research paper when to use et al

How Do You Use et al. in Scientific Papers? (with many examples)

Et al. in academic writing helps you cite a publication with multiple contributors. Exactly how and where to use it varies depending on the specific journal publication or prescribed style guide. Even experienced authors have trouble with “et al.” Here we help clarify its use across every major style guide.

Updated on June 15, 2022

In scholarly papers, citation rules definitely have some strange terms. Some aren't English, and some aren't words. The term “et al.”, for instance, isn't an English word. For someone who speaks a non-Latin-origin language, like Japanese or Arabic, it's especially confusing. This post explains the use of et al. and some common mistakes related to it.

You use “et al.” in academic writing to cite a publication that has multiple authors (or other contributors, such as editors). For example, instead of an in-text citation reading (Schouten, McAlexander, Smith, Rogers, & Koenig 2010), it would simply be (Schouten et al., 2010).

Et al. is used in manuscript body text and in reference lists and footnotes. Exactly how and where to use it varies depending on the prescribed style, such as APA, AMA, Harvard, Vancouver, or that of a specific publication. It's short for et alia (or the respective masculine and feminine plural et alii or et aliae) – Latin for “and others.” The abbreviation is required, but it also makes writing easier to read, helping the reader find the cited works faster.

Even experienced authors have trouble with “et al.” because many major academic writing style guides, as well as specific journals, use it slightly differently. Let's look at the main ones you'll typically see when you're seeking to publish your scientific manuscript. Some of these styles are updated regularly, so always be sure to check with your professor and/or with your target publication's guidelines.

Using et al. in the main academic referencing styles

The following sections will show how to use “et al.” in APA, MLA, Vancouver, and other main referencing styles, especially those found in journals.

APA (American Psychological Association) Style

APA is commonly used in the social sciences and medicine, both in universities and in publications. Keep up to date on the latest APA style as well.

For in-text citations in APA Style , when a source has two authors, list both authors by their last names, followed by the publication year. For three or more authors, cite the first author followed by “et al.”

Note that these rules are based on the Publication Manual of the American Psychological Association, Seventh Edition (APA 7). The previous versions required listing more authors in the in-text citations, and had some differences in the reference list requirements.

APA Style in-text citations

The main difference in APA Style in-text citations is their use of the ampersand (&) symbol. Et al. is now simply used for three-plus authors. It used to be more confusing, as up to five authors were listed at first reference and then et al. on second reference. Many will not be familiar with the current style, so be sure to check.

APA Style reference list

The “et al.” abbreviation is not used in the APA references list. But knowing how to prepare the list can help you know when to use et al. in the in-text citations.

For publications with 3–20 authors put all the authors. For example:

Eckhardt, G., Houston, M., Jiang, B., Lamberton, C., Rindfleisch, A. & Zervas, G. (2019). Marketing in the sharing economy. Journal of Marketing , 83(5), 5-27.

For a source with 20 or more authors put the first six authors, followed by an ellipsis (…) and then the final author. For example:

Pegion, K., Kirtman, B. P., Becker, E., Collins, D. C., LaJoie, E., Burgman, R., . . . Kim, H. (2019). The subseasonal experiment (SubX): A multimodel subseasonal prediction experiment. Bulletin of the American Meteorological Society , 100(10), 2043-2061.

APA Style is rather idiosyncratic with its combinations of spaces and commas. Be careful with those, especially if you have a picky adviser or run into a picky peer reviewer or journal editor.

MLA (Modern Language Association) Style

MLA Style is most commonly used in the humanities. Nothing makes it especially unique, but it has its own slight differences.

MLA Style in-text citations

Unlike APA Style, MLA Style doesn't use the year in the citation. Instead, it uses the authors' last names and the relevant page number.

Use “et al.” for sources with three or more authors for both in-text citations and in the references list.

MLA Style reference list

For the reference list, known as the Works Cited list in MLA Style, publications with three or more authors will look like this:

Wysocki, Anne Frances, et al. Writing New Media: Theory and Applications for Expanding the Teaching of Composition . Utah State University Press, 2004.

Vancouver Style

The Vancouver Style guide was developed in Canada by the International Committee of Medical Journal Editors (ICMJE) . It's now widely used for journal referencing in medicine, health sciences, and life sciences, and even in technology.

It's a concise style that works well for hyperlinking and with referencing software such as EndNote.

Vancouver Style in-text citations

Vancouver Style uses numbers for in-text citations, so using “et al.” is not a concern. However, if an author is named in a sentence, use “et al.” for publications with more than one author. For example:

“Holt et al. found that there was no histochemical evidence of mitochondrial myopathy.”

Vancouver Style reference list

For the reference list, put the names of up to six authors. For example:

Holt IJ, Miller DH, Harding AE. Genetic heterogeneity and mitochondrial DNA heteroplasmy in Leber's hereditary optic neuropathy. J Med Genet. 1989 Dec; 26 (12): 739-743 .

For seven or more authors put the first six and “et al.” For example:

Meakin CJ, King DA, White J, Scott JM, Handley H, Griffiths A, et al. Screening for depression in the medically ill. J Nerv Ment Dis 1991; 12: 45‐53 .

AMA (American Medical Association) Style

Also very common in medical referencing is AMA Style. AMA Style tends to be used for strictly clinical medical journals and the life sciences.

AMA Style In-text citations and reference list

The AMA system is similar to the Vancouver system in that it also uses numbers for in-text citations. The difference is found in the way AMA treats publications with seven or more authors in the reference list.

In AMA put the names of all the authors for up to six authors. For example:

Mizumoto K, Kagaya K, Zarebski A, Chowell G. Estimating the asymptomatic proportion of coronavirus disease 2019 (COVID-19) cases on board the Diamond Princess cruise ship, Yokohama, Japan, 2020. Euro Surveill. 2020;25(10):2000180.

For seven or more authors put the first three, followed by “et al.” For example:

Ahn DG, Shin HJ, Kim MH, et al. Current Status of Epidemiology, Diagnosis, Therapeutics, and Vaccines for Novel Coronavirus Disease 2019 (COVID-19). J Microbiol Biotechnol. 2020;30(3):313-324.

Chicago/Turabian Style

Chicago Style (and the very similar Turabian Style) is an American English style guide that is widely used in books in the social sciences and humanities, as well as journalism. It's less commonly used in journals.

The massive and comprehensive book called The Chicago Manual of Style (CMOS) has two referencing systems: author-date and notes and bibliography (which, by the way, LaTex can handle automatically).

Chicago Style in-text citations

Use of “et al.” is the same in both of the above referencing styles. For in-text citations put all last names when there are up to three authors. For four or more authors put the first author's name followed by “et al.”

For footnotes, but the full author name(s). Note that relevant page numbers are also usually given in Chicago Style. Also, unlike APA Style, the word “and” is used instead of the & ampersand symbol. Footnotes are usually indicated in the text with a superscript number.

Chicago Style reference list

For the reference list in Chicago Style, use all authors' full names if the source has up to 10 authors. For example:

Sechzer, Jeri A., S. M. Pfaffilin, F. L. Denmark, A. Griffin, and S. J. Blumenthal, eds. Women and Mental Health . Baltimore: Johns Hopkins University Press, 1996.

For more than 10 authors put the first seven, followed by “et al.”

Harvard Style

This style guide will be familiar for students who have studied in the US or under US professors. It's commonly used from the high school level upward. It's less common in scientific publications.

Harvard Style in-text citations

For in-text citations in Harvard Style put all names if the source has three or fewer authors. Use “et al.” if there are four or more authors. Just to make things even more confusing, Harvard usually does not put a comma between the author name or between “et al.” and the year.

Harvard Style reference list

For the reference list in Harvard Style put the names of all the authors, no matter how many there are. For example:

Lupien, S.J., McEwen, B.S., Gunnar, M.R. and Heim, C., 2009. Effects of stress throughout the lifespan on the brain, behaviour and cognition. Nature Reviews Neuroscience , 10(6), pp. 434-445.

Harvard style is primarily used in university settings, and each school may have its own variations. Be sure to check, because Harvard shows a lot of variety in punctuation and capitalization depending on the university or publication using it.

Specific journal variations

Despite the great number of referencing styles available, some journals prefer to use their own style of referencing. These are almost never 100% unique. Most often, they are based on a popular style, but with a few alterations.

Most commonly, Vancouver Style is used as a basis for making a publication's or journal's “house style” (see more on that topic below). Some add spaces. Some change the punctuation. Some use superscript numbers while others use numbers in parentheses or brackets.

For instance, the popular online open-access (OA) journal PLOS ONE states it uses Vancouver Style. It does, but it also places citation numbers in brackets and it removes spaces in some punctuation in the reference list. These are small differences, but an author must do them correctly or they risk having their submission rejected by their target journal .

Another example, the American Society of Agricultural and Biological Engineers (ASABE) , which produced journals including Transactions of the ASABE , uses a variation of APA Style 6th Edition. Why? We may never know. But if you're submitting to them, you must follow their guidelines.

To be sure you satisfy the guidelines you can hire a professional scientific editor who has done this task hundreds, even thousands, of times. We're skilled at spotting tiny differences in styles. It's part of an editor job.

Common mistakes in using et al. in academic writing

There are several common mistakes that authors of any level should be aware of when using et al.

Using et al. when you shouldn't

Knowing where you should and should not put et al. depends on the style guide you're following. That's all. However, some authors simply put use et al. when there's more than one author. That's just wrong.

The recent APA Style update also made things confusing for students and publication-seeking researchers, because some professors and journal reviewers will be following APA 6 while others will be updated to APA 7. Still others may not care. If you're not sure, ask.

Using the period in et al.

Maybe the most common problem in using et al. is knowing where to put the period. It should be after the “al.” and not after the “et”. This is because, as mentioned, “et al.” is an abbreviation of the Latin phrase “et alia.” The “et” is itself a word.

The “et al.” may be followed by any other punctuation. For example:

(Aaker et al., 2004)

Or it may not. It depends on the publication.

When et al. ends a sentence, use only one period. For example:

“This leads to a 40% reduction in food waste, as shown by Simpson et al.”

“Et al.” vs. “etc.”

“Et al.” and “etc.” are sometimes confused with each other. But they're completely different.

The abbreviation “et al.” is used for lists of authors (or other contributors). That's all. However, “etc.” ( et cetera , which is the Latin word for “and other similar things”) is used for lists or related items. For example:

“Riches et al. (2017) suggest that subcultures form around a variety of popular music styles (punk, hip hop, etc.), each with its own aesthetics and ethos.”

Final words on et al.

Although the basic concept behind using “et al.” is easy, each system is different. For journal submission, check the specifics. The journal may use a common style such as APA or Vancouver, but with a few custom differences. Some journals are very picky about this, some are not.

Even though the abbreviation is required, it adds readability. Modern scientific writing should be accessible and readable; so et al., though tricky, is a good thing .

If you need formatting for your manuscript to be sure you're using the right guidelines, scientific editors can do that for you. Journal guidelines are notoriously quirky and if English isn't your first language, they're even harder.

Professional scientific editors are trained in dealing with this. Many of us even enjoy it! Get a professional edit if you want to be sure you have your references totally consistent and pleasing to the journal editor's discerning eyes.

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Citations: Using et al.

Using et al..

For a work with one or two authors, include the name(s) in every citation. Here is how this could look:

(Dusek & Bakke, 2019)

According to Lai and Sookochoff (2018)…

In APA 7, for a work with three or more authors, list the first author and “et al.” for all citations, including the first citation, unless doing so would create ambiguity. (Note that this rule has changed from APA 6 guidelines on using "et al.," which recommend listing all author names in the first citation up to five authors but then using "et al." for the second and subsequent citations.)

Here is how this would look for a source authored by Sookochoff, Lai, and Bakke published in 2017:

(Sookochoff et al., 2017)

According to Sookochoff et al. (2017)...

Remember that there is no comma between the surname and "et al.," and the period goes only after the "al." The English translation of "et al." is "and others."

A helpful table of this rule can be found in APA 7, Table 8.1.

Shortening Citations With et al. Video

• APA Formatting & Style: Shortening Citations With et al. (video transcript)

Related Resources

Knowledge Check: Using et al.

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How to Use Et Al. in Every Format—Et Al. Meaning

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Written by  Scribendi

Have you ever come across "et al." and wondered what it meant? Or how to use it?

If so, you're not alone. This Latin phrase is commonly used in academic writing and can be confused with other Latin phrases like "etc."

Things get even more complex when you realize that the placement of et al. changes depending on what style guide you're using.

Read on for a simplified breakdown of how to use et al. in every format, so you never get stuck.

Et Al. Meaning

Before we get into the nitty-gritty details, it helps to first understand the literal definition of et al. That way, you'll know exactly what you're saying when you use the term.

The phrase "et al." is derived from the Latin phrase "et alia," which means "and others." You are likely to encounter et al. in the references, in-text citations, and reference lists of academic texts.

For example, you might see the phrase, "Horowitz et al. (2012) published groundbreaking research," which means that Horowitz and others published the research.

Why Is Et Al. Used?

Et al. is used to simplify citations within your text or reference list. It lets the reader know that other authors have contributed to the work you're citing, without you having to list every author.

Et al. is also used to simplify subsequent references to groups of coauthors that have already been cited in full. For example, if you're citing the same group over and over, using et al. can simplify that citation throughout your paper.

How to Write Et Al.

Where should i put the period.

The period in et al. should go at the end of "al" because "al" is an abbreviation for "alia," meaning "others."

There is no period after "et" because "et" isn't an abbreviation. It's a full word in Latin, meaning "and."

Remember, "et al." is the only correct way to type this phrase.

A trick for remembering to include the period after "al" is to think of another common abbreviation, "etc."

"Etc." abbreviates et cetera, meaning "and the rest," and it always requires a period at the end. So et al., which is similar, always takes a period at the end too.

Here are a few common misspellings of et al.:

When you use other punctuation with et al., like a comma, it goes after the period. But if you're ending a sentence with et al., you don't need an additional period.

Should I Italicize Et Al.?

Most major style guides (including APA, MLA, the Chicago Manual of Style, and Harvard) do not require et al. to be italicized. However, some field-specific publications do require the italicization of the phrase, so it's always a good idea to double-check.

Using et al. in a sentence appropriately varies among style guides. Check out the overviews of different style guides below to make sure you're using this tricky phrase correctly.

How to Use Et Al., with Examples

APA format, established by the American Psychological Association, is commonly used for publications, essays, reports, and books in the fields of psychology and social science.

Also called APA style, this format has established specific standards for scientific and scholarly writing. It encourages uniformity and consistency in the way content is organized and references are cited.

APA in-text citations, reference lists, and title pages adhere to formatting requirements that differ from those of other styles.

For example, APA includes the author's surname and publication year in in-text citations, using an ampersand if there are two authors:

(Smith, 2012)

(Smith & Jones, 2012)

Another differentiator between APA and other styles is that APA requires a cover page, called a Title Page, and uses the title "References" above the citation list at the end of papers or manuscripts.

Traditionally, APA format is used for a range of subjects in the social and behavioral sciences, including:

Linguistics

When to Use Et Al. in APA

When dealing with a work by three or more authors in APA format (seventh edition), use the first author's last name in the signal phrase or parenthesis, followed by et al.

(McKenzie et al., 2020)

McKenzie et al. (2020)

Keep in mind that et al. wouldn't be needed if you were citing just two authors. If you were citing two authors and you replaced one of their names with et al., meaning "and others," this would be incorrect.

Use et al. in APA in-text citations only if you're citing at least three authors, and remember that et al. is never used in the reference list in APA.

Et Al. Example in APA Format

The use of et al. in APA format differs from other styles when it comes to the References.

Its format requires listing the surnames and first initials of up to 20 authors, placing an ampersand before the final author.

Karloff, J., McMahon, S., Watson, C., Williamson, M., Russell, S., Holden, R., Williams, B., Messier, A., Nesbo, J., Lamott, A., Shaffer, M., Barrows, A., Perry, T., Rooney, K., Cruz, M., Warren, G., Granville, D., Gonzalez, R., Johnson, S., & Galloway, J.

For more than 20 authors, you would replace all authors after the 19th with ellipses, followed by the final author's name.

Karloff, J., McMahon, S., Watson, C., Williamson, M., Russell, S., Holden, R., Williams, B., Messier, A., Nesbo, J., Lamott, A., Shaffer, M., Barrows, A., Perry, T., Rooney, K., Cruz, M., Warren, G., Granville, D., Gonzalez, R., Johnson, S., … Galloway, J.

Et Al. in APA In-Text Citations with Multiple Authors

When citing three or more authors in text with APA (seventh edition), you can use et al. upon the first and subsequent references to a source.

Before the seventh edition of APA, the names of up to five authors had to be spelled out in the text. Et al. could only be used upon subsequent references.

Luckily, the seventh edition has been simplified. Here is an example of how to use et al. for in-text citations in APA.

Three or more authors:

Parenthetical: (Johnson et al., 2020)

Nonparenthetical: Johnson et al. (2020)

MLA format was developed by the Modern Language Association. It provides specific guidelines for students and researchers writing academically in the fields of language and literature.

Often called MLA style, this format allows for an easy reading experience. It offers a uniform and consistent method of adding citations to books or literature.

Using et al. in MLA is different from APA and other styles in its requirements for the use of et al. MLA has different standards for layout, citations, and abbreviations.

There are also slight differences in the way authors are cited. But the spelling of et al. is always the same, regardless of the style guide being used, with lowercase letters and no punctuation after "et"—the only punctuation is the period after "al."

MLA format is traditionally used by writers and students creating work in the following disciplines:

Language and literature

Comparative literature

Literary criticism

Cultural studies

If you're formatting an essay or paper in MLA, the most updated edition is the ninth, published in April 2021.

When to Use Et Al. in MLA

You can use et al. in MLA when referring to multiple authors—three or more, to be exact. And you can add et al. to both your in-text citations and your Works Cited page (the name for the reference list).

Et Al. Example in MLA Format

Let's look at how to cite multiple authors in MLA in your Works Cited page with et al.

See the following two examples for citing a collection of poems and a collection of stories using et al. in MLA.

O'Hara, Frank, et al. The Collected Poems of Frank O'Hara . University of California Press, 1995.

Levine, Robert S., et al. The Norton Anthology of American Literature . Ninth ed., W.W. Norton &

Company, 2022.

Note that the second line of the citation is indented by half an inch.

Et Al. in MLA In-Text Citations with Multiple Authors

Now, we'll review how to cite multiple authors using et al. in MLA in-text citations.

MLA format requires the inclusion of the first author's surname, then et al., and then the page number.

(Lackey et al. 56)

The above is an example of a parenthetical in-text citation with et al. Here is an example of how to incorporate it within your prose:

According to Gilbert et al., "Today, however, we can see more clearly just how complex and multifaceted Woolf's set of women writers really is" (23).

The Chicago Manual of Style, often called CMS, CMOS, or Chicago, is a style guide used by authors, editors, indexers, designers, and publishers to prepare manuscripts and to aid in the revision of grammar, punctuation, and usage.

Dubbed the "editor's bible," the Chicago Manual of Style is typically used with material intended for publication. It's the style most often applied to novels, blogs, and creative nonfiction.

A key differentiator of Chicago style is that it offers two systems for source citations: notes and bibliography or author-date.

The notes and bibliography system is used by scholars and writers working in the humanities, and the author-date system is preferred by writers in the fields of science and social science.

That being said, here are a few of the most common fields in which Chicago style is used:

Social science

Natural science

The most recent edition is the 17th, which was published in September 2017. Let's look at how to use et al. in Chicago style.

When to Use Et Al. in Chicago Style

In essays adhering to Chicago style, you can use et al. when citing a source with four or more authors.

The format and placement of et al. can vary because, as we mentioned earlier, Chicago uses two systems for source citation: notes and bibliography and author-date. So the placement really depends on which system you're using!

But as a general rule, you can use et al. in your in-text citations, in your footnotes and endnotes, and in your reference list at the end of your document.

Note that bibliographies go with the notes and bibliography system, and reference lists go with the author-date system.

Et Al. Example in Chicago Style

You will use et al. in bibliographic form in Chicago Style for sources with more than 10 authors. In such cases, you'll list the first seven authors, followed by et al.

The citation format in your bibliography will change depending on whether you're using the notes and bibliography system or the author-date system, but the placement and format of et al. are the same.

Notes and bibliography system:

Jackson, Tiffany D., Nic Stone, Ashley Woodfolk, Dhonielle Clayton, Angie Thomas, Nicola Yoon,

Natasha Schrader, et al. Blackout . New York, NY: Quill Tree Books, an imprint of

HarperCollins Publishers, 2021.

Author-date system:

Natasha Schrader, et al. 2021. Blackout . New York, NY: Quill Tree Books, an imprint of

HarperCollins Publishers.

Et Al. in Chicago Style In-Text Citations with Multiple Authors

When using et al. in an in-text citation of four or more authors, et al. can be formatted in a few different ways, depending on which source citation system you're using. Take a look at the examples below.

In the author-date system, et al. goes after the first author's surname in an in-text citation.

(Johnson et al. 2021, 465)

In the notes and bibliography system, et al. can go in a short or long footnote. Here's how the format breaks down for each type:

Short footnote: Johnson et al.

Long footnote: David Johnson et al.

Turabian style is similar to Chicago style when it comes to how to write et al. Published by Kate L. Turabian in 1937, this style was created for researchers and students. Its official title is A Manual for Writers of Research Papers, Theses, and Dissertations.

You can think of it as a student's version of Chicago style. Turabian style places greater emphasis on student needs regarding the formatting of papers and citations, and this is its biggest differentiator.

This manual is also shorter and contains fewer instructions than others. Another differentiator of Turabian is that it covers a wide spectrum of disciplines, including:

Art history

Social studies

Global studies

Religious studies

If you're looking for the latest edition, be sure to use the ninth, published in 2018.

When to Use Et Al. in Turabian Style

As in Chicago style, you can use et al. in a sentence in Turabian when citing four or more authors.

You can also use et al. when citing sources in both the main text and the bibliography, and this is true of both the notes and bibliography and the author-date citation systems.

Where you should put et al. and how you should format it will vary depending on which citation system you use. Just keep in mind that you can use et al. in Turabian style whenever you have four or more authors to cite.

Et Al. Example in Turabian Style

The great thing about using Turabian style is that if you understand how to use et al. in Chicago style, using it in Turabian will be a breeze.

Below are some examples of how to write et al. in either your bibliography (notes and bibliography system) or reference list (author-date system) in Turabian style.

Notes and bibliography system (book):

Using the Turabian citation system, you'll follow the same format for et al. Only the placement of the publication date changes. See the examples below.

Kitamura, Katie, Allen Johnson, Birk Meyer, Alex Fritas, Joan Bigsby, Becca Thomas, Greg 

Lewis, et al. A Separation . New York: Riverhead Books. 2017. 

Author-date citation system (book):

For more than 10 authors, list the first seven authors and follow them up with et al.

Kitamura, Katie, Allen Johnson, Birk Meyer, Alex Fritas, Joan Bigsby, Becca Thomas, Greg Lewis,       

et al. 2017. A Separation . New York: Riverhead Books. 

Et Al. in Turabian In-Text Citations with Multiple Authors

Using et al. in your in-text citations is the same in Turabian as it is in Chicago style. You'll put et al. in your footnotes (short and long) and within your text. Below are examples of each.

(Johnson et al. 2017, 45)

In the notes and bibliography system, et al. could go in a short or long footnote. Here's how the format breaks down for each type of footnote.

Short footnote: Weber et al.

Long footnote: Jesse N. Weber et al.

Harvard style is a popular formatting style across many universities. It's been known to go by a couple of different names, including the Harvard Referencing System and Author-Date Referencing.

There's no official connection between Harvard style and Harvard University. This style is simply another way for students to cite their sources and format their papers uniformly.

Common disciplines that use this style include the following:

Behavioral sciences

The thing to remember about Harvard style is that it isn't as cut-and-dried as other styles—different schools have different requirements. This means that using et al. in Harvard style can change depending on what school you go to.

Be sure to refer to your professor's instructions before using et al. in your papers.

For the purposes of this post, we'll be talking about how to use et al. following Harvard Business School's Citation Guide.

When to Use Et Al. in Harvard Style

While some aspects of Harvard style can vary across institutions, one thing everyone seems to agree on is that et al. should be used to cite four or more authors.

So you should use et al. when you're citing four or more authors in both your footnotes and in your bibliography. You can also use the term in both parenthetical statements and as a signal phrase.

Et Al. Example in Harvard Style

In the bibliography section of your paper, you can use et al. for academic citations of sources with four or more authors .

Unlike Chicago, you don't have to list a certain number of authors before you list et al.—you can simply use et al. after the first author's name.

Here are two examples, one for a book citation and one for a web citation:

Christensen, C. Roland, et al. Business Policy: Text and Cases . 5th ed. Homewood, IL: Richard 

D. Irwin, Inc., 1982.

Enright, Michael J., et al. "Daewoo and the Korean Chaebol." University of Hong Kong case no. 

HKU143 (University of Hong Kong, August 2001). Harvard Business Publishing. 

https://hbsp.harvard.edu/, accessed March 2007.

Et Al. in Harvard Style In-Text Citations with Multiple Authors

When it comes to using et al. in Harvard style in-text citations, you can use it in your footnotes, parenthetical phrases, and signal phrases.

See examples of each below.

³C. Roland Christensen et al., Business Policy: Text and Cases, 5th ed. (Homewood, IL:

Richard D. Irwin, Inc., 1982), p. 101.

Parenthetical phrase:

(Johnson et al. 2007)

Signal phrase:

Johnson et al. (2007)

Again, keep in mind that Harvard style gives your instructor leeway in their guidelines for how to format et al., so be sure to follow their instructions.

An additional way to cite references is to use Vancouver style. This style was developed in Vancouver in 1978 by medical journal editors. It is most commonly used in medicine and science.

The biggest difference between Vancouver and other styles is its use of numbers. Often called the Numbering System, Vancouver cites sources by placing numbers within parentheses or superscripts in the main text.

These citation numbers are tied to entries in your reference list. Like in other styles, your reference list in Vancouver style will have all of the sources you've cited within your text.

Some common fields that use Vancouver are as follows:

Biomedicine

As in Harvard style, keep in mind that some universities and organizations have their own specific formatting requirements when it comes to citing work with et al. in Vancouver style.

When to Use Et Al. in Vancouver Style

With Vancouver style, you can use et al. for both in-text citations and within the reference list.

You should use et al. in your reference list when citing more than six authors. If you're citing just six authors, you'll need to spell out each author's surname and first initial, separating each author with a comma.

You should use et al. within the main text when citing multiple authors. Some universities differ in terms of how many authors, so it's best to check with your institution to confirm its preferences for this style.

Et Al. Example in Vancouver Style

Let's start our et al. examples for Vancouver with those in bibliographic form.

In Vancouver style, the bibliography is called a reference list. You'll add et al. to reference entries only if you're listing more than six authors. List the first six authors, then add et al.

Here's an example of a book citation with et al. in the reference list:

Doornbos MM, Groenhout ER, Hotz GK, Brandsen C, Cusveller B, Flikkema M, et al. 

Transforming care: a Christian vision of nursing practice. Grand Rapids, Michigan: 

William B. Eerdmans Publishing Company; 2005.

Note that the authors' surnames are followed by their first and (in many cases) middle initials, without punctuation.

Here's an example for an electronic journal article:

Aho M, Irshad B, Ackerman SJ, Lewis M, Leddy R, Pope T, et al. Correlation of sonographic

features of invasive ductal mammary carcinoma with age, tumor grade, and 

hormone-receptor status. J Clin Ultrasound [Internet]. 2013 Jan [cited 2015 Apr 

27];41(1):10-7. Available from: https://onlinelibrary.wiley.com/doi/10.1002/jcu.21990/full 

DOI: 10.1002/jcu.21990

Et Al. in Vancouver Style In-Text Citations with Multiple Authors

As far as in-text citations go in Vancouver style, you can use et al. directly in the text, followed by a reference number.

Because Vancouver references sources within parentheses or superscripts, here are examples using et al. in-text with both systems:

Harrison et al. (5) agree that only one solution is viable.

Harrison et al. 5 agree that only one solution is viable.

Et Alibi, Et Alii, and Others

Sometimes, et al. can be confused with other Latin phrases like et alibi and et alii. This is understandable because the terms all begin with the same letters!

Don't worry. Over the next few sections, we'll break down what each of these phrases means. That way, if you need to use them in your next paper or article, you won't use them incorrectly.

Et alia is the Latin phrase for "and others," and the phrase "et al." is its abbreviated form.

Et alia is meant to be used when a list contains too many people or things to name. In academic writing, it is used when citing sources with multiple authors.

However, the full phrase "et alia" isn't typically spelled out in academic writing. In papers, journals, and manuscripts, the abbreviated form "et al." is used, with a period after "al."

Et alibi means "and elsewhere" in Latin. It's used in academic writing to show that the information you're citing is mentioned in other parts of a text, too.

For example, if you're citing a passage from the Bible that can also be found in other locations of the text, that would be a perfect instance for using et alibi.

Keep in mind that "et al." is the abbreviated form of both et alibi and et alia.

Et aliae also means "and others" but in the feminine plural form. This means that et aliae refers specifically to a group of women or girls.

However, you won't need to differentiate between feminine or masculine forms when using et al. in your writing. You would simply use "et al."—the abbreviated form of both.

The Latin phrase et alii means "and others" in the masculine plural form. It’s used to refer to a group of men or boys.

But the abbreviated form, "et al.," is still what you would use to cite multiple authors.

As long as you can remember how to write the abbreviation et al. in your papers, you're good to go!

Difference between Et Al. and Etc.

Do you ever confuse et al. with etc.? You're not alone. The two are very similar.

While et al. means "and others" in Latin, etc. is short for the Latin et cetera and means "and the rest."

Both phrases indicate that something has been omitted from the text, and both are abbreviations. However, there are key differences to keep in mind to avoid using them incorrectly in your paper.

You use etc. to shorten a list. Its use lets the reader know that there are more items or examples you could list but that the shortened list allows the reader to get the idea.

For example, if you were to write, "The event is at the beach, so bring your swimsuits, towels, sunscreen, sandals, etc.," readers know they need to bring all beach items, not just the ones mentioned.

Similarly, you use et al. to shorten a list of authors or collaborators.

Common Mistakes

Spelling and formatting Latin phrases is no walk in the park—especially when you need to get them right to earn a passing grade.

It also doesn't help that each style guide has its own formatting or that many Latin phrases can sound the same. It's enough to make your head spin!

Below, we'll cover common mistakes made when using et al. and why using it is so important for clear and concise academic writing.

Spelling Latin phrases can be tricky, but abbreviating them correctly can be even trickier.

When using et al. in your papers, be sure to abbreviate it correctly and to use the right punctuation.

Et al. is always spelled as two separate words—"et" and "al"—with a period after "al."

The best way to remember how to punctuate and spell it is to remember that it's an abbreviation.

Here are a few common misspellings of et al. so you know to avoid them:

Using the Incorrect Style

Spelling et al. correctly is only half the battle. You'll also need to be sure you're using et al. in the style required by your university, institution, or professor.

As we mentioned earlier, there are many style guides to choose from, including MLA, Chicago, APA, and Turabian.

Each style has its own specific format for et al., so be sure to study its guidelines carefully before adding et al. to your references.

You'll especially want to take note of how et al. is used in both in-text and reference list citations and how many authors necessitate its use.

Not Using Et Al.

Using et al. is a clear and concise way of communicating your source information to readers without overwhelming them or taking away from your work.

It lets readers know that multiple authors or collaborators contributed to the source without having to list them all. Also, when referencing a source with several authors or collaborators multiple times, the use of et al. keeps the writing neat and tidy.

Not using et al. would make academic writing awkwardly long and arduous within the main text while extending bibliographies and reference lists unnecessarily.

Et al. helps academic writers and authors reference their sources in a clean-cut way.

How to Cite a Tweet

Nowadays, it's not uncommon for students or researchers to turn to social platforms like Twitter for their research.

Because of this, styles like MLA, APA, and Chicago have stayed current by offering standards for formatting citations of Tweets in research papers and scholarly articles.

Each style has its own formatting requirements for citing a Tweet, and these can vary among different editions of the same style.

Below are instructions for citing Tweets in each of the three major styles.

To cite a Tweet in MLA (ninth edition), you'll cite the first name and surname of the account holder (or the name of the organization) in addition to the Twitter handle.

Here is the basic structure:

Surname, First name [Username]. "Tweet message." Twitter , date posted, URL.

Here's an example:

Swift, Taylor [@taylorswift13]. "I'm so proud of this song and the memories I have with you guys 

because of it." Twitter , 22 November 2021, 

twitter.com/taylorswift13/status/1462908809542787072.

To cite a Tweet from an organization in MLA, you'll use this structure:

Organization or Account Name [Username]. "Tweet message". Twitter , date posted, URL.

The Wall Street Journal [@WSJ]. "Activist hedge fund Trian has acquired a stake in Unilever, 

people familiar with the matter say, adding pressure on the consumer-goods company." 

Twitter , 23 January 2022, twitter.com/WSJ/status/1485356694972551171.

To cite a Tweet in APA style (seventh edition), you'll do things a little differently from MLA. APA requires only the author's full surname with the first name initialized.

You'll also include only the first 20 words of the Tweet in your reference.

Surname, Initials [@username]. (Year, Month Day). Text of Tweet [Tweet]. Twitter. URL

Gates, B. [@BillGates]. (2019, September 7). Today, it's difficult for researchers to diagnose 

#Alzheimers patients early enough to intervene. A reliable, easy and accurate diagnostic 

would [Thumbnail with link attached] [Tweet]. Twitter.  

https://twitter.com/BillGates/status/1170305718425137152

To cite a Tweet in Chicago style, you'll include many of the same elements as Tweet citations in other styles, but you'll also add a timestamp.

The general structure is as follows:

First name Surname (@TwitterHandle), "Text of Tweet," Twitter, Month Day, Year, 00:00 

a.m., link to Tweet.

Here's an example from the Chicago Manual of Style:

Conan O'Brien (@ConanOBrien), "In honor of Earth Day, I'm recycling my Tweets," Twitter, April 

22, 2015, 11:10 a.m., https://twitter.com/ConanOBrien/status/590940792967016448.

If you'd like to cite a Tweet within your text, here's an example using the above Tweet:

Conan O'Brien's Tweet was characteristically deadpan: "In honor of Earth Day, I'm recycling my Tweets" (@ConanOBrien, April 22, 2015).

Frequently Asked Questions

What does et al. mean in a citation.

In a citation, et al. indicates that multiple authors are being cited within a reference in an academic work but that not all of their names are listed.

It's not uncommon for some sources to have 10 or even 20 authors, given the collaborative nature of research in the fields of medicine and science. Using et al. is a way of ensuring that all authors are referenced without crowding the content.

When Should Et Al. Be Used in APA Style?

Use et al. in APA in-text citations with multiple authors, as well as in the References. Specifically, use it when dealing with a work by three to five authors. You'll use the first author's surname in the signal phrase, parenthetical statement, or bibliographic entry, followed by et al.

Keep in mind that you should use et al. only for three or more authors, not two. Since et al. is an abbreviation for "and others," it must stand in for more than one person. If you were trying to cite two authors and you used et al. after the first one, et al. would represent one person as opposed to several "others," which would be incorrect.

What Is Et Al. in MLA?

In MLA style, et al. is an abbreviated Latin phrase meaning "and others." It indicates that multiple authors contributed to the source being cited but that not all of them are listed.

MLA recommends using et al. for sources with three or more authors. Et al. can be used both within the main text and on the Works Cited page. It's punctuated in the same way as in other styles, with a period after "al" only.

Here is a citation example using et al. in MLA:

(Gubar et al. 56)

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How to Use Et Al. Effectively in Your Research Paper

Discover how to use et al correctly and easily with this step-by-step guide. Learn the rules and examples of using et al in academic writing.

Academic writing is full of various citation styles and abbreviations, and one of the most commonly used ones is “et al.” But what does it really mean, and how should you use it? 

When there are three or more writers, this Latin phrase, short for “et alia,” is used instead of mentioning all of them. While it may appear simple, correctly using “et al.” can be difficult, and many writers struggle to understand when and how to use it.

This article will go over everything you need to know about utilizing “et al.” in your research paper, from what it is to how to cite it.

What Is Et Al.? 

“Et al.” is a common acronym in academic writing to denote the presence of other writers who are not expressly mentioned. It comes from the Latin phrase “et alia” (which means “and others” in English). The use of Latin terms in academic writing extends back to the medieval period when Latin was the main scholarly language in Europe.

When a source contains three or more authors, it might be difficult to list all of them in a citation, especially when there is a large list of authors. In these specific situations, “et al.” might be used to indicate the presence of other authors who are not identified.

It’s worth noting that the use of “et al.” differs based on the citation style. In certain styles, such as APA and Chicago , “et al.” is used for sources with three or more authors, however, in MLA style, “et al.” is only used for sources with four or more writers in others.

How To Use Et Al.?

Here are some guidelines for effectively using “et al.” in academic writing:

• Use “et al.” when a source has a large list of authors: When there are several authors of a source, the term “et al.” is used to shorten the citation, and it is commonly used when there are three or more writers; nevertheless, verify your citation style guidelines. 
• After the first author’s name, add “et al.” Most citation styles, including APA and MLA, include “et al.” after the first author’s name in the citation. 
• The period should come after “al.”. For instance, “Smith et al.” is correct, however, “Smith et. al” is wrong.
• In academic writing, “et al.” is italicized but not capitalized. 
• Understand the citation style guidelines: The use of “et al.” varies depending on the citation style. Make sure to follow the citation style guidelines specified for your academic writing.

In general, “et al.” is a useful abbreviation that simplifies citations in research papers, and mastering its correct usage is crucial for producing clear and precise academic writing.

Et Alibi, Et Alii, And Others

One important piece of information concerning et al. is the different forms it may take. Here’s some more information on all the different forms of “et al.” and their meanings:

Et alia is the most fundamental and widespread form of “et al.” in academic writing, meaning “and others.” When the number of authors of a source exceeds the maximum allowed by a citation style, this phrase is commonly used in citations to denote multiple authors.

Et Alibi 

Another Latin term for “and elsewhere.” It is used to highlight that further information about a topic is available from another source or location. For example, if you’re referencing a source and there’s more material on the same issue in another source, you might say “et alibi” to indicate that other sources are available. 

In Latin, this is the feminine plural form of “et al.” It is used to show that a source has numerous female authors. For instance, if a source includes numerous female authors and you wish to highlight this in your citation, you may use “et aliae” rather than “et al.”

In Latin, this is the male plural form of “et al.” It is used to show that a source has numerous male authors. For instance, if a source includes numerous male authors and you wish to highlight this in your citation, you may use “et alii” rather than “et al.”

Difference Between Et Al. And Etc.

Et al. and etc. are two separate abbreviations used in academic writing.

Et al. is an abbreviation of the Latin term “et alia,” which translates as “and others.”, as previously stated. It is used in citations to show many authors of a source and is usually used amid a citation, after the first author’s name. Simply put, you may use “et al.” to indicate that there are other authors aside from the name mentioned. 

Etc. is an abbreviation of the Latin term “et cetera,” which means “and so forth” or “and other things.” It is used to show that a list of things extends beyond those specifically mentioned. For instance, if you’re presenting several examples of a specific topic, you may use “etc.” to show that there are more examples. The expression “Etc.” is commonly used at the conclusion of a list and is preceded by a comma. It is frequently followed by a period and, depending on the citation style, italicized.

In summary, “et al.” indicates numerous authors of a source in a citation, whereas “etc.” indicates a continuation of a list of items.

Common Mistakes

• Using “et al.” to indicate a list continuation: As previously stated, “et al.” should be used to denote multiple authors of a source and should not be used to suggest a list continuation.
• Using “etc.” to denote many authors: “Etc.” should never be used to denote multiple authors of a source. This is the responsibility of “et al.” and using “etc.” instead is considered wrong and deceptive.
• Capitalizing “et al.” and “etc.”: Both “et al.” and “etc.” are abbreviations and should be written in lowercase characters, unless at the beginning of a phrase.
• Using “and others” instead of “et al.”: It is more suitable in academic writing to use “et al.” instead of “and others” to denote multiple authors of a source. Using “and others” can be informal and may violate the citation style.
• Using “et cetera” instead of “etc.”: The acceptable abbreviation for “et cetera” is “etc.” and should be used instead. Using the entire sentence may be considered needless, and it may also take up precious space in a citation or text.

How To Cite Et Al.

Here’s how to properly quote “et al.” in several citation styles:

In MLA style, “et al.” is used after the first author’s name on the paper’s reference page. For example, if a source has three or more authors, you would list the first author’s name followed by “et al.”, example:

Smith, John, et al. “The Effects of Climate Change on Biodiversity.” Environmental Science Journal, vol. 27, no. 2, 2020, pp. 25-34.

For in-text citations, you would include the first author’s name followed by “et al.” and at the end, the page number should be enclosed in parentheses, for example: 

(Smith et al. 36).

In the references page, put “et al.” after the first author’s name. If a source includes three or more authors, you would list the first author’s name followed by “et al.”, example:

Smith, J., Johnson, A., Williams, K., & Brown, M. (2019). “The Impact of Social Media on Adolescent Mental Health.” Journal of Adolescent Health, 65(3), 42-51.

In-text citations would include the first author’s name in parenthesis, followed by “et al.” and the year of publication, for example:

(Smith et al., 2019).

Chicago Format

On the reference page, “et al.” is used after the first author’s name in Chicago style. If a source includes four or more authors, you would list the first author’s name followed by “et al.”, for example:

Jones, S., et al. “The History of the American Civil War.” Civil War History, vol. 55, no. 2, 2009, pp. 34-47.

In-text citations would include the first author’s name in parenthesis, followed by “et al.” and the page number:

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When to Use Author “et al.” in Citation and References

We publish because we want to share our knowledge and because we want recognition for our work. We acknowledge people’s ideas and findings by providing citations. Unfortunately, however, the rules regarding this common practice are not always easy to decipher, even for the best of us! We have published a number of other articles that help you navigate citation requirements, for example on the best citation format for science papers, how many references you should include in your research paper, and the general differences between common citation styles .

This article focuses on how to name the authors of cited works, including when to use the abbreviated Latin term “et al.” that usually accompanies the phrase “author et al.” Please make sure to follow the relevant journal guidelines concerning punctuation, citation style, etc., as publishers do not always follow the exact same formatting rules. Let’s start with some general definitions, and then look at specific rules of the most common style guides .

Table of Contents:

• What are the main types of citations? 
• Why do we use “et al.” in citations? 
• Using “et al.” vs “etc.”
• When Do We Use “et al.” in Citations? 

How to Cite “et al.” in APA Style

• How to Cite “et al.” in Chicago
• How to Cite “et al.” in MLA Citations

What are the main types of citations?

When referring to published literature, you need to provide details so that others can find and review the original material you base your ideas and claims on. In your research paper, you can make references to source materials using either endnotes and footnotes (i.e., numbers in the text that refer to the bottom of the page or the end of the paper) or in-text citations. Both styles require you to also provide a reference list at the end of the document.

In-text (or parenthetical) citations

When referencing other literature by author name or title in the text paragraphs of your paper, you are using in-text citations . Another similar method of citing is using parenthetical citations , as the referencing information is usually placed within parentheses. Both of these citation types are common in APA style.

Endnotes and footnotes

Endnotes and footnotes help declutter your writing. They are simple notation systems that allow you to use numbers in the body of a text to reference a cited work. Each number corresponds to further information or a citation entry found at the end of a manuscript (for endnotes) or at the bottom of the page where the cited reference is mentioned (for footnotes).

Footnotes are rarely found in scientific writing but are frequently used in the humanities and social sciences. Additionally, endnotes often replace parenthetical in-text citations in scientific journals these days – make sure you pay attention to the journal guidelines when you prepare your manuscript so that you don’t have to suddenly change your entire citation style before submitting or during the review process.

Reference lists

A reference list compiles all the works cited within a document for ease of reference and is included at the end of a manuscript. It must be included regardless of how the source material is acknowledged within the main body of your article. The author guidelines of your target journal will tell you whether the list has to be ordered alphabetically or in order of appearance in the text (when using a numbered system), and what general style it has to adhere to.

Why do we use “et al.” in citation?

The Latin term “et al.” is short for “et alii” and means “and others.” The abbreviation is used when citing a source with multiple authors. Its function is similar to that of “et cetera”, another common Latin phrase that is usually abbreviated as “etc.” and means “and other similar things.”

Using “et al.” vs “etc.” in Citation and References

As stated above, “et al.” is used strictly when talking about people, while “etc.” is only used for things. Apart from this key difference, they have the same function: replacing a list.

When to Use “et al.” in Reference and Citation

We cannot stress this enough, but always double-check your journal or relevant style guide regarding Latin terms and citations. There is no uniform rule on when to use “et al.”, but at least the phrase’s spelling is consistent. Always write “et al.” in lowercase and include a period after “al.”, even when it appears in the middle of a sentence.

The abbreviation “et al.” replaces author names in endnotes, footnotes, and in-text citations; it depends on the target journal whether “author et al.” citation style can also be used in the reference list or whether all author names need to be spelled out in that section . In the following section, you will find further information on how to cite references according to the most common citation styles and examples.

The APA style is frequently used in social science publications. Examples of book and journal citations are provided below. For information about other sources and special cases, see the Publication Manual of the American Psychological Association , Seventh Edition (2020) .

In-text or parenthetical citations (author-date system)

APA style uses the author-date notation, and the in-text citation rules apply to both digital and print editions of books and journals. Also, while providing page number references is optional for paraphrased statements, the APA recommends including them. Also, note that APA style uses the ampersand (&) to list author names in parentheses.

The same author rules apply to all source media including books, print periodicals, electronic journals, etc. Also, since reading electronic journals has become the norm for academics, the APA recommends including a DOI number for each journal article referenced, even if you accessed the document in print. Do not include a period (.) after the DOI information. Also note that APA reference lists should not contain “et al.”, and that the author-number thresholds for formatting rules in the reference list are different from those for in-text citations specified above.

The APA style does not use footnotes and strongly discourages the use of endnotes, which should only provide tangential information. However, sometimes content notes are necessary. In such cases, use the notation covered in Section 2.12 of the  APA Publication Manual .

How to Cite “et al.” in Chicago Style

The Chicago style is commonly used in the humanities. Below, we only comment on general book and journal citation formats. For additional information, see Wordvice’s guide on the Chicago Manual of Style , 17th edition . For an example of an annotated paper that uses bibliographic notation (i.e., numbers that refer to sources in a list), see the Pu rdue Owl’s NB sampler. See an example of an author-date paper.

Note that for formally published online sources, such as electronic academic journals, you do not need to include access date information except if required by your publisher or discipline. If no DOI is available, provide the uniform resource locator (URL). Unlike APA style, Chicago style does NOT use the ampersand (&) in name lists; instead, use “and.” Additionally, an author’s given names (first and middle) should be written in full (no initials) unless the author consistently publishes using initials.

Using “et al.” in in-text or parenthetical citations (author-date system)

Parenthetical citations are more commonly adopted by authors in the social, physical, and natural sciences. The same notation is used for digital and print editions of books and journals.

Don’t use “et al.” in reference lists

Using author “et al.” in books

Using author “et al.” in journals

Using “et al.” in endnotes and footnotes (bibliographic system)

How to cite “et al.” in mla style.

The MLA style is commonly used by writers in the humanities. General book and journal citation formations are highlighted below. For information regarding other media and special cases, see Wordvices guide on the MLA Handbook style rules .

Using “et al.” in in-text (parenthetical) citations

The MLA style uses an author-page style instead of an author-date style.

Using “et al.” in the reference list (works cited page)

Using “et al.” in endnotes and footnotes.

The MLA style does not generally encourage endnotes and footnotes; however, it does accommodate their use when needed to clarify points that don’t otherwise belong in the main body of your work. The formats for these notes are similar to the format used for in-text citations, but without the parentheses:

One author : See [last name] [page range]

See Johnson 5-15 for a further discussion of this phenomenon.

Multiple authors/studies:  

[Comment]. See [last name] [page range], [last name] [page range], [last name] [page range]

Several other studies make the same argument. See, for example, Walker and Francis 112-118, Thomson 20-43, and Muller 78-90.

Regarding [content topic], see [last name] [page range] and [last name] [page range]; for [content topic], see [last name] [page range], [last name] [page range], and [last name] [page range].

Regarding this phenomenon’s impact on trauma caretakers, see Miller 54-68 and Willis 23-25; for alternative explanations, see Jones 23-25, Thompson 64-55, and Smith 12-15.

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How to Use "et al."

What is the meaning of “et al.”.

"Et al." is an abbreviation for the Latin phrase "et alii" or "et alia," which translates to "and others" in English. It is used to indicate that there are additional authors or contributors beyond those explicitly mentioned.

In academic and scholarly writing, "et al." is commonly used in citations, reference lists, and bibliographies to represent multiple authors (three or more) when citing a source. It is an efficient way to acknowledge all contributors without listing all of the names, especially when there are numerous authors involved.

For example, if a research paper has several authors, the first citation may include all authors’ names, but all following in-text citations may use "et al." to refer to them collectively. This means that the first time the article is referenced, the author would state “Williams, Clark, and Fisher (2010)”. Every time that same article is mentioned after that, the author would write “Williams et al. (2010)”.

How to Use “et al.” in Citations

Here's another example of how “et al.” is used in a citation:

- First citation: Anong, Johnson, Anderson, and Brown (2022)

- Subsequent citations: Anong et al. (2022)

By using “et al.”, the reader understands that there are three or more additional authors not explicitly listed in the citation.

It’s important to note that the usage and formatting of “et al.” varies depending on the citation style or guidelines you are following. Each style guide, such as APA, MLA, or Chicago, has its own rules for using “et al.” for in-text citations and reference lists. You need to consult the appropriate style guide for the specific rules and conventions of your chosen citation style.

Some journals do not require you to follow a specific style guide, but do request that you keep your reference formatting consistent. If you’re submitting to the Journal of Economic Psychology , for example, “references can be in any style or format as long as the style is consistent.”

Using “et al.” in Reference Lists

In a reference list or bibliography, “et al.” is sometimes used to indicate multiple authors for a particular source. This applies for some , but not all, style guides. Here's an example:

   - For an article with multiple authors: Anong, S., Solis, O., et al. (2022). Title of the article. Journal Name , Volume (Issue), Page range.

   Note: The first few authors’ names (up to and including three authors) are listed, followed by “et al.” to indicate additional authors.

It’s important to follow the specific citation style recommended by your academic institution or the guidelines provided by the publication you are writing for. Different citation styles, such as APA, MLA, or Chicago, may have specific rules for using “et al.” in citations. Make sure to consult the appropriate style guide for the specific formatting and citation requirements.

APA Style “et al.”

In APA (American Psychological Association) style, “et al.” is used to represent multiple authors in in-text citations and reference lists. Here's how “et al.” is used in APA style:

1. Et al. in-text citations:

For sources with three or more authors: In the first in-text citation, list all the authors’ names. In subsequent citations, use the first author's last name followed by “et al.” and the publication year. For example:

     - First citation: (Anong, West, Anderson, & Brown, 2022)

     - Subsequent citations: (Anong et al., 2022)

 For sources with two authors: Always include both authors’ names in the in-text citation, connected by an ampersand (&). For example:

     - (Anong & West, 2022)

2. Reference list:

   - List up to 20 authors: Include the names of all authors in the reference list.

   - List more than 20 authors: After the 19th author's name, use an ellipsis (...) and then include the last author's name. For example:

     Anong, S., Johnson, A., Anderson, B., ... Brown, C.

Remember to follow the specific APA guidelines for your particular source type, such as journal articles, books, or websites. This is important because there may be slight variations in formatting and punctuation for each type.

It’s necessary to consult the official APA Publication Manual (currently the 7th edition) or online resources provided by the APA for comprehensive guidance on citing sources and using “et al.” correctly in APA style.

“Et al.” in a Sentence

One example of using “et al.” in a sentence following APA Style if the authors are Zhong, Xiao, and Su is: “Zhong et al. (2005) found a gender difference in behavior.” This could also be written as “Research has shown a gender difference in behavior (Zhong et al., 1995). Note that the first time the paper by Zhong et al. (2005) is noted, all authors’ names would be included: “Zhong, Xiao, and Su (2005) found a gender difference in behavior.”

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You should use et al . in your citations when a source you have used has 'four or more' (ie more than three) authors.  You should list all of the authors in your reference.

What is et al. .

et al. stands for ' and others ' and it should be used in your   in-text citations  only,  to indicate that a work has multiple authors.  In your reference list at the end of your work, you should include  all of the authors.

It should  only  be used if the source you are citing has  four or more  authors (ie more than three). Where a source has one, two or three authors, you should name them all in both your in-text citation and your reference.

et al . should always be written in italics, with a full stop at the end of  al .

Previously, if you were a student at SGUL, you were required to use et al . in both your citation and your reference list, so this is a change.

Find some examples of the correct use below:

Books or ebooks with four or more authors (more than three)

You should use Davey  et al ., 2015 in your citation but list all of the authors in your reference list.  For example: Citation: Davey et al . (2015) discuss the mechanisms of antibacterial drugs....

Davey, P., Wilcox, M.H, Irving, W. and Thwaites, G. (2015) Antimicrobial chemotherapy . 7th edn. Oxford: Oxford University Press.

Articles with four or more authors (more than three)

You should use Glavin  et al ., 2021 in your citation but list all of the authors in your reference list. For example:

Citation: Chronotype is a biological factor that affects sleep (Glavin et al ., 2021, p.2637).

Glavin, E.E., Ceneus, M., Chanowitz, M., Kantillerakis, J., Mendelow, E., Mosquera, J. and Spaeth, A.M. (2021) 'Relationships between sleep, exercise timing, and chronograph in young adults' Journal of Health Psychology, 26(13), pp. 2636-2647.

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Enago Thesis

How to effectively use "et al." in apa, mla, and chicago style.

In academic writing, referencing and citation are crucial for giving credit to the authors of the sources used and avoiding plagiarism. However, in cases where multiple authors have contributed to a source, it can be tedious and repetitive to list all their names in every instance of citation. This is where the abbreviation "et al." comes into play. In this article, we will discuss what et al. means, how to use it in every format, and common mistakes to avoid.

What is Et al.? Why is it used?

"Et al." is a Latin used in academic writing to avoid the repetition of a long list of authors in reference lists or in-text citations. It is an abbreviation for "et alia," which means "and others" in English.

It is particularly useful when citing sources with multiple authors, such as academic papers, books, or journal articles. By using et al., you can condense the list of authors to just the first author's name and "et al.," which is especially helpful when dealing with citations that have more than three authors.

For example, if a research paper has four authors, instead of listing all the authors every time their names are mentioned, the first author's name is followed by "et al." after the first mention. This helps to simplify the text and reduce repetition.

The correct way to use "et al." in a citation depends on the citation style being used. In general, it is used for in-text citations and in the reference list or bibliography to indicate that there are multiple authors.

Et al. in Referencing

In-text citations with et al. should be used when citing a source that has three or more authors. When citing the source for the first time, all the authors' names should be included, separated by commas. For example, "According to Smith, Johnson, and Brown (2019)..." When citing the source again, "et al." can be used instead of listing all the authors' names. For instance, "As previously noted (Smith et al., 2019)..."

In reference lists or bibliographies, et al. is used to refer to sources with multiple authors. When listing the authors in the reference list, the first author's name should be listed in the standard format, followed by a comma and "et al." For example, "Smith, J., et al. (2019). Title of the source."

Proper formatting of et al. in different citation styles

Different citation styles have varying guidelines on how to use et al. Here are some examples of how to use et al. in different citation styles:

APA style:  In in-text citations, use "et al." when there are three or more authors. For reference lists, the first author's name is listed, followed by "et al." For example, "Smith, J., et al. (2019). Title of the source."

MLA style:  In in-text citations, use "et al." when there are three or more authors. In the Works Cited list, the first author's name is listed, followed by "et al." For example, "Smith, John, et al. Title of the source. Publisher, Year."

Chicago style:  In in-text citations, use "et al." when there are four or more authors. In the bibliography, the first author's name is listed, followed by "et al." For example, "Smith, John, et al. Title of the source. Publisher, Year."

Examples of using et al. in APA, MLA, and Chicago Style

Jones, A., Smith, B., Johnson, C., et al. (2020). The effects of climate change on marine biodiversity. Science, 367(6485), 979-983.

Jones, Adam, et al. "The Effects of Climate Change on Marine Biodiversity." Science, vol. 367, no. 6485, 2020, pp. 979-983.

Jones, Adam, Bob Smith, Carol Johnson, et al. "The Effects of Climate Change on Marine Biodiversity." Science 367, no. 6485 (2020): 979-983.

Et Alibi, Et Alii, and Others

In addition to "et al.," there are other Latin phrases that are sometimes used in academic writing, including "et alibi" and "et alii."

"Et alibi" means "and elsewhere" and is often used to refer to sources that are cited elsewhere in the same work. For example, if a source is cited in one chapter and then referenced again in another chapter, the second citation may use "et alibi" instead of repeating the full citation.

"Et alii" means "and others" and is sometimes used interchangeably with "et al." However, "et alii" can also be used to refer to groups of people or things that are not authors. For example, "et alii" may be used to refer to multiple members of a research team or to multiple participants in a study.

It's worth noting that while these phrases have similar meanings, they are not always interchangeable. It's important to understand the context in which they are being used and to use them appropriately.

Difference Between Et Al. and Etc.

While "et al." and "etc." are both Latin abbreviations used in academic writing , they have different meanings and uses.

"Et al." means "and others" and is typically used in reference to multiple authors of a work, particularly when citing sources with more than three authors. For example, "Jones et al. (2021) found that..." would indicate that there are additional authors besides Jones who contributed to the work being cited.

"Etc." is short for "et cetera," which means "and so forth" or "and other things." It is typically used to refer to a list of additional items or examples that are not explicitly listed. For example, "The study examined the effects of diet, exercise, stress reduction, etc. on overall health" would indicate that there are additional factors being considered beyond the three specifically mentioned.

Common Mistakes to Avoid While Using Et al.

• Incorrectly using "et al." with single-author sources: "Et al." should only be used when there are multiple authors of a work. If there is only one author, the full name should be used in the citation.
• Not including enough author names: While "et al." is used to shorten a list of authors, it's important to include enough names to accurately identify the source. In general, if there are four or fewer authors, all names should be listed in the citation.
• Inconsistent use of "et al." in the same work: If "et al." is used to shorten a list of authors in one citation, it should be used consistently throughout the rest of the work.
• Incorrect placement of punctuation: The period should be placed after "al" and should not be italicized. For example, "Jones et al. (2021)" is correct, while "Jones et al. (2021)" is incorrect.
• Not using "et al." when necessary: If there are more than three authors of a work, "et al." should be used to shorten the citation. Failing to do so can make the citation unnecessarily long and cumbersome to read.

In conclusion, using et al. is a useful tool for academic writing , allowing for concise and efficient referencing of sources with multiple authors. Be sure to use it correctly and follow the guidelines for your chosen citation style. By doing so, you will avoid plagiarism and give proper credit to the authors of the sources used in your writing.

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How to Use ‘‘et al.’’ in APA Style (7th Edition)

The term ‘‘et al.’’ is the abbreviated form of the Latin term ‘‘et alia,’’ which means ‘‘and others.’’ It is used in academic in-text citations when referring to a source with multiple authors. In APA style, for a source with three or more authors, list the first author’s last name and “et al.” for all citations, including the first citation.

The Term ‘‘et al.’’ is the Abbreviation of Latin Term ‘‘et elia,’’ Meaning ‘‘and others’’

The term ‘‘et al.’’ is the abbreviated form of the Latin term ‘‘ et alia,’’ which means ‘‘and others.’’ It is used in academic in-text citations when referring to a source with multiple authors. In APA style, for a source with three or more authors , list the first author’s last name and “et al.” for all citations, including the first citation. Note that this rule has changed from APA 6th edition guidelines on using ‘‘et al.’’  which recommend listing all author names in the first citation up to five authors but then using ‘‘et al.’’  for the second and subsequent citations.

In October 2019, the American Psychological Association (APA) introduced the 7th edition of the APA Publication Manual, which replaces the 6th edition. The in-intext citation for works with three or more authors is now abbreviated right from the first citation. You only include the first author’s name and  “et al.”

For two authors: Always cite both authors' names in-text everytime you reference them.

Here is how this would look for a source authored by Parker, Robin, and Williams published in 2018.

( Parker et al., 2018)

            or

Parker et al. (2018) claimed that…

Note that there will be no comma between the surname and  ‘‘et al.’’  but a comma should be placed before the date in parentheses citation.  Also, the period goes only after the  ‘‘al.’’     even when it falls in the middle of a sentence.

The Correct Use of ‘‘et al.’’

Authors make several mistakes when using ‘‘et al.’’ in academic writings. The “al” in “et al.” is always followed by a period because the period shows that it is the abbreviated form of the term ‘‘et alia.’’

Thus, the following forms are not correct: ‘‘ et al’’, ‘‘et. al’’, ‘‘et. al.’’

The proper use of the abbreviation is ‘‘et al.’’

Also, “et al.” can be directly followed by another punctuation where necessary. However, the period always comes first:

(Parker et al., 2018)

When “et al.” is used right at the end of a sentence, only one period is used:

... by Parker et al. (2018)

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For more information about the citation styles and APA style, read the following articles:  

The 9 Most Important Changes in the 7th Edition of the APA Manual

APA Manual 7th Edition: In-Text Citation

How to Present Tables and Figures in APA Style (7th edition)

How to Use et al. in APA Style (7th Edition)?

APA Style: In-Text Citation | Reference List Entry

How to Cite Sources in APA Referencing Style? | With APA 7th Edition Update

How and When to Use ”et al.” in APA In-Text Citations?

Citation Styles | Which Citation Style Should I Use?

APA Formatting Guide for Academic Manuscripts

This handout discusses how and when to use et al. in APA style (7th edition). To give you an opportunity to practice your proofreading, we have left a few spelling, punctuation, or grammatical errors in the text. See if you can spot them! If you spot the errors correctly, you will be entitled to a 10% discount.

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Whenever you use words, facts, ideas, or explanations from other works, those sources must be cited. Academic referencing is required when you have copied texts from an essay, an article, a book, or other sources verbatim, which is called quotation. You also need referencing when you use an idea or a fact from another work even if you haven’t used their exact expression.

The American Psychological Association (APA) introduced the 7th Edition of the APA Publication Manual in 2019. This edition replaced the previous one, the 6th Edition of the manual. Since then, several things have changed. The latest edition also updated listing web pages in the 7th edition of the APA Manual Publication

Academic referencing and academic citing acknowledge the sources used by authors in their manuscripts. It necessitates the linkage of citations to the list of works cited in a paper. It also gives credit to the sources of information used in the manuscript. Whether it is about writing a book or other academic documents, you first need to learn how to use APA referencing style and format. With the help of citations, readers can easily understand the messages conveyed in an article.

Home / Guides / Citation Guides / MLA Format / How to use et al. in MLA

How to use et al. in MLA

When you need to cite sources that have three or more authors or contributors, you don’t have to cite all of the contributors’ names. Instead, you can use et al.

Et al. is an abbreviation for the Latin word, et alii, which means “and others.” Using et al. shows that three or more contributors wrote, edited, or collaborated on the work, even though only one name is listed in the citation.

Using et al. in MLA

There are many places in mla citation style where you can use et al..

• Works with three or more writers
• Works with three or more editors
• Collections of essays, stories, or poems with three or more contributors

Citing a journal article in MLA is a common instance where you may need to use et al., as journal articles often have three or more authors.

When to use et al.

You can use et al. in both your MLA in-text citations and the Works Cited page. When using et al., you should always use the name of the writer listed first in the source material.

Note: Using et al. should not be confused with etc. or other abbreviations that indicate more content than listed. For example, etc. is an abbreviation for et cetera and is used at the end of a list to indicate that there are other similar items included in the list that are not names.

How to Format et al. in MLA Style

The format to write et al. is always the same: et al. Use lowercase letters with no punctuation after et and a period after al.

To format an in-text citation

• Use the first writer’s last name. Use the first writer listed on the source material. Do not use any of the other writers’ names.
• Follow the last name with et al. Write et al. in lowercase letters. There is no punctuation after the et, and there is always a period after the al.
• Other end punctuation can come after the period following al., but you must include the period because this is an abbreviation.

Example et al. citations for the following source

• Title: “Interrogating Disciplines/Disciplinarity in WAC/WID: An Institutional Study”
• Author(s): Anne Ruggles Gere, Sarah C. Swofford, Naomi Silver and Melody Pugh.
• Source: College Composition and Communication , vol. 67, no. 2, 2015, pp. 243–266

In-text citation example

(Gere et al. 243)

The Works Cited page citation for that source

Gere, Anne Ruggles, et al. “Interrogating Disciplines/Disciplinarity in WAC/WID: An Institutional Study.”  College Composition and Communication , vol. 67, no. 2, 2015, pp. 243–266. JSTOR , www.jstor.org/stable/24633857.

NOTE: A comma is needed after the name before et al. in the works cited citation, but it is not required for the in-text citation example.

Works cited

Gere, Anne Ruggles, et al. “Interrogating Disciplines/Disciplinarity in WAC/WID: An Institutional Study.”  College Composition and Communication , vol. 67, no. 2, 2015, pp. 243–266., www.jstor.org/stable/24633857. Accessed 6 Oct. 2020.

MLA Handbook . 9th ed., Modern Language Association of America, 2021.

Published October 25, 2020.

By Catherine Sigler. Catherine has a Ph.D. in English Education and has taught college-level writing for 15 years.

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What does ‘et al.’ mean and How to Use ‘et al.’ in a Research Paper

A majority of researchers wonder how to use et al. in a research paper. Et al. is one of the most commonly used Latin abbreviations, just like as,  etc. ,  versus ,  circa ,  ibid.  and  id. , and often crops up in academic writing. While the English phrases of all these above mentioned words are acceptable, researchers use Latin abbreviations as they take less time and fewer characters to write. Yet it’s not always easy to get these right.

In this article, we focus on one such abbreviation – et al. by explaining what does et al. mean and how to use et al. in a research paper correctly

Table of Contents

Et al. definition: what does et al. mean in academic writing, how to use et al. in a research paper, how to use et al. in a research paper: common mistakes to avoid.

The number of co-authors in an academic publication is, in principle, unlimited. Imagine having to write the names of all the authors in your bibliography. This is where et al. comes into play to indicate other authors in an academic work.

Et al. is the abbreviated form of et alia (or et alii or et aliae, the masculine and feminine plural, respectively). According to the Cambridge Dictionary, 1 the synonyms for et al. are “also,” “extra,” and “in addition.” Et al. is mostly used to indicate more than two people; it can also simplify subsequent references to groups of co-authors already cited in full. For example, when citing the same group of authors multiple times in your paper, using et al. can simplify the citations.

The number of authors to be listed before et al. can vary depending on the style guides. A few guidelines on the proper use of et al. in citations and references are given below. 2

• APA Style Guide
• Reference list : Et al. is never used in the reference list in APA.
• In-text Citation : Use et al. only if citing at least three authors (seventh edition). Use the first author’s last name in the signal phrase or parenthesis, followed by et al. For example,

Parenthetical: (Smith et al., 2020)

Nonparenthetical: Smith et al. (2020)

• MLA Style Guide
• Reference list : Use et al. when referencing work with three or more authors; include only the first author, followed by a comma, and the words et al, ending with a period.
• In-text Citation : Use et al. when citing a work with three or more authors. The author name is followed by the page number in place of the year. For example,

Parenthetical: …(James et al. 157-65).

Nonparenthetical: James et al. (157-65)

• Chicago Style Guide
• Reference list : When a source has more than 10 authors, list the first seven followed by “et al.” Otherwise, list every author.
• In-text Citation : When a source has four or more authors, give only the first author’s name followed by “et al.” For example,

(Bay et al. 2017, 465)

• Vancouver Style Guide
• Reference list : When a source has more than six authors, list the first six followed by “et al.” Otherwise, list every author.
• In-text Citation : When a source has three or more authors, give only the first author’s name followed by “et al.” Use et al. directly in the text, followed by the reference number. For example,

Doornbos et al. (5) agree that only one solution is viable.

• Plural vs. singular: Wondering if et al. is a plural or singular verb? Whenever this confuses you, remember that because a phrase ending in “et al.” refers to a group of people, you will use plural verbs when the “et al.” phrase is the subject.

Incorrect: Smith et al. (2015) states that …

Correct: Smith et al. (2015) state that …

Also, “et al.” is plural and indicates at least two people. So, you cannot use et al. to substitute for only one author. For example, if you are dealing with three authors and have typed out two names, the last author cannot be replaced with et al.

• Punctuation: “Et al.” is commonly misspelled as “et all,” “et. al.,” “et. al,” or “et-al.” Remember, “et al.” is composed of two words, with the “al” always followed by a period. The period indicates that the term is an abbreviation.
• Using the incorrect style: Decide on the style guide to follow before you start your writing. The use of et al. in a sentence can vary if using APA, MLA, etc.
• Possessive noun: When using a possessive noun, use “ ’s ” after “et al.”

Correct: In Smith et al.s’ study.

Correct: In Smith et al.’s study.

But, it’s best to avoid possessive phrasing when using et al. Instead, change it “Smith et al. (2015) found that . . .” or “In a study by Smith et al.”

• Italics: Italicizing is unnecessary when using “et al.” But this is more of a style guideline and can vary.
• “Et Al.” vs. “Etc.” and “Et Alibi”: “Et al.,” is sometimes confused with “Etc.” and “et alibi” but they mean different things and have other usages. “Etc.” meaning “rest,” is used at the end when listing things rather than people. “Et Alibi” means “and elsewhere” and is used when listing places or locations.

Finally, remember that when you think of the meaning of et al. in research, it is a word used to indicate other authors in the list. It is not intended to highlight the first author’s contribution as more important than the others, but simply to save space and time.

• Cambridge Dictionary https://dictionary.cambridge.org/dictionary/english/et-al
• Purdue Online Writing Lab. APA Formatting and Style Guide (7 th edition) https://owl.purdue.edu/owl/research_and_citation/apa_style/apa_formatting_and_style_guide/general_format.html

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In-Text Citations: Author/Authors

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Though the APA's author-date system for citations is fairly straightforward, author categories can vary significantly from the standard "one author, one source" configuration. There are also additional rules for citing authors of indirect sources, electronic sources, and sources without page numbers.

A Work by One Author 

The APA manual recommends the use of the author-date citation structure for in-text citation references. This structure requires that any in-text citation (i.e., within the body of the text) be accompanied by a corresponding reference list entry. In the in-text citation provide the surname of the author but do not include suffixes such as "Jr.". 

Citing Non-Standard Author Categories

A work by two authors.

Name both authors in the signal phrase or in parentheses each time you cite the work. Use the word "and" between the authors' names within the text and use the ampersand in parentheses.

A Work by Three or More Authors

List only the first author’s name followed by “et al.” in every citation, even the first, unless doing so would create ambiguity between different sources.

In  et al. , et  should not be followed by a period. Only "al" should be followed by a period.

If you’re citing multiple works with similar groups of authors, and the shortened “et al” citation form of each source would be the same, you’ll need to avoid ambiguity by writing out more names. If you cited works with these authors:

They would be cited in-text as follows to avoid ambiguity:

Since et al. is plural, it should always be a substitute for more than one name. In the case that et al. would stand in for just one author, write the author’s name instead.

Unknown Author

If the work does not have an author, cite the source by its title in the signal phrase or use the first word or two in the parentheses. Titles of books and reports are italicized; titles of articles, chapters, and web pages are in quotation marks. APA style calls for capitalizing important words in titles when they are written in the text (but not when they are written in reference lists).

Note : In the rare case that "Anonymous" is used for the author, treat it as the author's name (Anonymous, 2001). In the reference list, use the name Anonymous as the author.

Organization as an Author

If the author is an organization or a government agency, mention the organization in the signal phrase or in the parenthetical citation the first time you cite the source, just as you would an individual person.

If the organization has a well-known abbreviation, you may include the abbreviation in brackets the first time the source is cited and then use only the abbreviation in later citations. However, if you cite work from multiple organizations whose abbreviations are the same, do not use abbreviations (to avoid ambiguity).

Two or More Works in the Same Parentheses

When your parenthetical citation includes two or more works, order them the same way they appear in the reference list (viz., alphabetically), separated by a semi-colon.

If you cite multiple works by the same author in the same parenthetical citation, give the author’s name only once and follow with dates. No date citations go first, then years, then in-press citations.

Authors with the Same Last Name

To prevent confusion, use first initials with the last names.

Two or More Works by the Same Author in the Same Year

If you have two sources by the same author in the same year, use lower-case letters (a, b, c) with the year to order the entries in the reference list. Use the lower-case letters with the year in the in-text citation.

Introductions, Prefaces, Forewords, and Afterwords

When citing an Introduction, Preface, Foreword, or Afterword in-text, cite the appropriate author and year as usual.

Personal Communication

For interviews, letters, e-mails, and other person-to-person communication, cite the communicator's name, the fact that it was personal communication, and the date of the communication. Do not include personal communication in the reference list.

If using a footnote to reference personal communication, handle citations the same way.

Traditional Knowledge of Indigenous Peoples

When citing information you learned from a conversation with an Indigenous person who was not your research participant, use a variation of the personal communication citation above. Include the person’s full name, nation or Indigenous group, location, and any other relevant details before the “personal communication, date” part of the citation.

Citing Indirect Sources

Generally, writers should endeavor to read primary sources (original sources) and cite those rather than secondary sources (works that report on original sources). Sometimes, however, this is impossible. If you use a source that was cited in another source, name the original source in your signal phrase. List the secondary source in your reference list and include the secondary source in the parentheses. If you know the year of the original source, include it in the citation.

Electronic Sources

If possible, cite an electronic document the same as any other document by using the author-date style.

Unknown Author and Unknown Date

If no author or date is given, use the title in your signal phrase or the first word or two of the title in the parentheses and use the abbreviation "n.d." (for "no date").

Sources Without Page Numbers

When an electronic source lacks page numbers, you should try to include information that will help readers find the passage being cited. Use the heading or section name, an abbreviated heading or section name, a paragraph number (para. 1), or a combination of these.

Note:  Never use the page numbers of webpages you print out; different computers print webpages with different pagination. Do not use Kindle location numbers; instead, use the page number (available in many Kindle books) or the method above. 

Other Sources

The  APA Publication Manual  describes how to cite many different kinds of authors and content creators. However, you may occasionally encounter a source or author category that the manual does not describe, making the best way to proceed unclear.

In these cases, it's typically acceptable to apply the general principles of APA citation to the new kind of source in a way that's consistent and sensible. A good way to do this is to simply use the standard APA directions for a type of source that resembles the source you want to cite. For example, a sensible way to cite a virtual reality program would be to mimic the APA's guidelines for computer software.

You may also want to investigate whether a third-party organization has provided directions for how to cite this kind of source.

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Use of et al. – for referencing in an academic paper

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“Et al.” is a popular expression used by college and university students when citing a research source having more than one author. Included in this article is its definition, how to use it when using different citation styles, and the most frequently asked questions regarding the use of et al. The information contained here is vital, as it will assist you to know how to use the term correctly, which may, in the long run, help in boosting your grades.

Inhaltsverzeichnis

• 1 Use of et al. - FAQ
• 2 Use of et al.: Definition
• 3 Use of et al. in Citation
• 4 Use of et al. Common Mistakes
• 5 In a Nutshell

Use of et al. - FAQ

When do you need to use et al..

Et al. is an abbreviation of et al. ii, a Latin expression, which means ‘and others’. You often need to make use of et al. in a citation that has three or more authors. Its purpose is to assist in making the citations manageable. If you are using the author’s name, you have to ensure you add a full stop after writing et al.

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How do you punctuate et al.?

Some college students don’t know how to make the right use of et al. Whenever you have to use the term, you have to note that the “al” should always have a period after it. The period is vital because et al. is an abbreviation . Including the period helps to show this to the reader.

How do you read et al.?

Learning the use of et al. also means learning how to pronounce it. If reading it aloud, you will be required to pronounce the term in full, i.e., “et alia” or “et al. ii”. On the other hand, you could also choose to say “and others.” It’s the same way you would opt to say “for example,” as opposed to reading the abbreviation “e.g.”

Can you start an email with et al.?

Not sure how to make use of et al. in an email? It’s possible to do so. For example, in the greeting section, you could say Dear Daniel et al., Hello, Kevin et al., Remember that the expression stands for “and others.”

Should et al. be Italicized?

When using et al., you shouldn’t underline or italicize it. You have to write it without either of the two. As a rule, the most commonly used Latin abbreviations and words shouldn’t be italicized.

Use of et al.: Definition

Definition 1: et al. and others: It’s an abbreviation of ‘et alii’ which is used when the author is referring to a group of people. Definition 2: et al. and elsewhere: Authors use it when they want to refer to other occurrences in the text. Why it’s used: When citing papers that use the name and dating system, it can prove awkward when the author provides a long string containing numerous names. It’s the reason why many scientific journals recommend that authors make use of et al. When it’s used: Its recommended to try to make use of et al. when an author doesn’t want to have to name all the things or people in a list. The abbreviation works in the same manner as “etc.”

Use of et al. in Citation

Using Et Al. in APA Citation

APA citation happens to have a few quirks, with one of them being in the use of et al. While the abbreviation is used when citing sources having many authors, the 7th APA citation edition happens to differ from the rest in terms of how to make use of et al.

Only make use of et al. when using in-text citations

The 7th edition states that et al. should only be used when one is using in-text citations. It’s a significant change from the previous edition where authors could use et al. in the reference list. This means that the reference list in the 7th edition doesn’t support the use of et al.

In-text citation format using et al.

Et al. should only be used in in-text citations when an author wants to reference a source having three or more authors. Here, you can make use of et al. by including the authors first name, and then including et al. in every other Citation.

Exceptions: Multiple works sharing a single author

There are instances when making use of et al. could lead to unwanted problems. For example, when numerous works share the same three authors and year of publication, simply writing “et al.” could muddy the waters. When dealing with such a case, it’s recommended to write as many names as possible to help differentiate the references. You can then make use of et al. for any remaining names.

Using Et Al. in MLA Citation

For MLA citation , it’s recommended that you make use of et al. whenever there are sources with more than three sources. It’s a rule that applies to both the Works Cited list and the in-text citations.

Using Et Al. in Chicago Citation

Chicago Style Citation traditionally has two citation systems: author-date style and notes and bibliography style. The use of et al. doesn’t differ in both styles. When working with sources with one, two, or three plus authors, you will need to list all their names in your in-text citations (author-date or footnotes).

In case you have a source with four-plus authors, then it’s advisable to use et al. by listing the first name and following it up with et al. In the Chicago style bibliography or reference list, you will need to list up to ten authors. For any source with over ten authors, you should list the first seven and then follow this with et al.

For example, Harold Peters, McDonnel, Anne Elliot, Frederick, Robert Davis, Molly Davidson, Ronald Clobus, Jessica Singh, et al.

Use of et al. Common Mistakes

I. Most students tend to make use of et al. with works that don’t have multiple sources. Remember, you only need to use it when the source has more than three authors. II. Punctuation Mistakes: the “al” in “et al.” should always have a period after it. The reason for using the period is because “et al.” is an abbreviation. It’s why you need the period.

• Where necessary, it can also be followed by another punctuation mark where deemed necessary. However, make sure that the period comes first, before the other punctuation mark.

III. Et al. vs etc. Some students end up confusing “etc.” with et al. This shouldn’t happen as “etc.” is used for concepts and lists of things whereas “et al.” is primarily used when dealing with lists of people.

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In a Nutshell

• Et al. is an abbreviation for a Latin term “et alia” which means “and others.”
• The expression is commonly used in academic papers when a writer wants to cite more than one author
• Each citation style has its own rules on how to use et al. in both the in-text citations and in the works cited section.
•  Common FAQs on making use of et al. have to do with reading it aloud and punctuating it correctly.

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Error bars indicate SDs.

Other includes American Indian or Alaska Native, Middle Eastern or North African, Native Hawaiian or other Pacific Islander, or none of these categories can fully describe the participant. Multiple races correspond to those who self-identified as more than 1 race and ethnicity category. All trends were statistically significant at P  < .05. Error bars indicate 95% CIs.

All trends were statistically significant at P  < .05. Error bars indicate 95% CIs.

The exploratory mediation analysis estimated that 46% (95% CI, 35%-61%) of the temporal trend in age at menarche was explained by BMI at menarche. Total effect represents the overall change in age at menarche per 10-year lapse in birth year, direct effect represents the proportion of this change that is independent of BMI z score at menarche, and indirect effect represents the proportion of this change mediated through BMI z score at menarche. Error bars indicate 95% CIs.

eMethods. Detailed Exclusion of Individuals With Potentially Inaccurate Time to Regularity Information

eFigure 1. Conceptual Model of the Research Question and Potential Mechanisms

eFigure 2. Flowchart of Participants in This Study

eFigure 3. Percentage of Participants in Each Time to Cycle Regularity by Age at Menarche

eFigure 4. Percentage of Participants With Predicted Time to Cycle Regularity Across Birth Year Categories, With Age at Menarche Fixed at the Mean (12.2 Years of Age)

eFigure 5. Temporal Trends of Time to Cycle Regularity by Birth Year Category, Stratified by Race/Ethnicity

eFigure 6. Temporal Trends of Time to Cycle Regularity by Birth Year Category, Stratified by Socioeconomic Status (SES)

eFigure 7. Temporal Trends of BMI Across Age Categories, Based on BMI z Scores and Percentiles Using the CDC Growth Chart (N = 9865)

eFigure 8. Predicted Mean Age at Menarche Across Birth Years by Race/Ethnicity, When Adjusted for BMI at Menarche

eTable 1. Characteristics of the Subset of 9865 AWHS Participants Who Provided Self-Recalled Weight and Height at Menarche, Overall and by Birth Year Category

eTable 2. Age at Menarche and Time to Cycle Regularity Measures by Birth Year Groups, Stratified by Race/Ethnicity

eTable 3. Age at Menarche and Time to Cycle Regularity Measures by Birth Year Groups, Stratified by Socioeconomic Status

eTable 4. Effect Estimates for the Temporal Trend in Age at Menarche, Mutually Adjusted for Race/Ethnicity and Socioeconomic Status

eTable 5. Age at Menarche and Time to Cycle Regularity Measures by Birth Year Groups, Stratified by Geographical Region

eTable 6. Effect Estimates for the Temporal Trend in Age at Menarche and Time to Regularity, Accounting for BMI at Menarche

eTable 7. Causal Mediation Analysis for the Temporal Trends in Time to Regularity Measures Among 8752 Participants With BMI z-Score at Menarche (Mediator)

Data Sharing Statement

• Menstruation as the Next Vital Sign JAMA Network Open Invited Commentary May 29, 2024 Lauren C. Houghton, PhD

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Wang Z , Asokan G , Onnela J, et al. Menarche and Time to Cycle Regularity Among Individuals Born Between 1950 and 2005 in the US. JAMA Netw Open. 2024;7(5):e2412854. doi:10.1001/jamanetworkopen.2024.12854

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Menarche and Time to Cycle Regularity Among Individuals Born Between 1950 and 2005 in the US

• 1 Department of Environmental Health, Harvard T.H. Chan School of Public Health, Boston, Massachusetts
• 2 Department of Biostatistics, Harvard T.H. Chan School of Public Health, Boston, Massachusetts
• 3 Epidemiology Branch, Division of Intramural Research, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, Durham, North Carolina
• 4 Health, Apple Inc, Cupertino, California
• 5 Department of Epidemiology, Harvard T.H. Chan School of Public Health, Boston, Massachusetts
• Invited Commentary Menstruation as the Next Vital Sign Lauren C. Houghton, PhD JAMA Network Open

Question   In the US, what are the temporal trends in age at menarche and time from menarche to cycle regularity?

Findings   This cohort study of 71 341 US female individuals born between 1950 and 2005 found significant trends toward earlier menarche and longer time to regularity over time, and these trends were more pronounced among those who were non-Hispanic Black, Asian, or of other or multiple races (compared with non-Hispanic White individuals) and among low socioeconomic status groups. Body mass index at menarche partially mediated the trend for menarche.

Meaning   These findings suggest that early-life menstrual characteristics have been trending in directions that indicate higher risk of later adverse health outcomes, which may contribute to health disparities.

Importance   Early menarche is associated with adverse health outcomes. Trends toward earlier menarche have been observed in the US, but data remain limited on differences by sociodemographic factors and body mass index (BMI). Time from menarche to cycle regularity is another understudied early-life characteristic with health implications.

Objectives   To evaluate the temporal trends and disparities in menarche and time to regularity and explore early-life BMI as a mediator.

Design, Setting, and Participants   This ongoing cohort study enrolled participants from an ongoing mobile application–based US cohort from November 14, 2019, to March 20, 2023.

Exposures   Birth year (categorized as 1950-1969, 1970-1979, 1980-1989, 1990-1999, and 2000-2005).

Main Outcomes and Measures   Main outcomes were age at menarche and time to regularity, which were self-recalled at enrollment. In addition, early (aged <11 years), very early (aged <9 years), and late (aged ≥16 years) age at menarche was assessed.

Results   Among the 71 341 female individuals who were analyzed (mean [SD] age at menarche, 12.2 [1.6] years; 2228 [3.1%] Asian, 3665 [5.1%] non-Hispanic Black, 4918 [6.9%] Hispanic, 49 518 [69.4%] non-Hispanic White, and 8461 [11.9%] other or multiple races or ethnicities), 5223 were born in 1950 to 1969, 12 226 in 1970 to 1979, 22 086 in 1980 to 1989, 23 894 in 1990 to 1999, and 7912 in 2000 to 2005. The mean (SD) age at menarche decreased from 12.5 (1.6) years in 1950 to 1969 to 11.9 (1.5) years in 2000 to 2005. The number of individuals experiencing early menarche increased from 449 (8.6%) to 1223 (15.5%), the number of individuals experiencing very early menarche increased from 31 (0.6%) to 110 (1.4%), and the number of individuals experiencing late menarche decreased from 286 (5.5%) to 137 (1.7%). For 61 932 participants with reported time to regularity, the number reaching regularity within 2 years decreased from 3463 (76.3%) to 4075 (56.0%), and the number not yet in regular cycles increased from 153 (3.4%) to 1375 (18.9%). The magnitude of the trend toward earlier menarche was greater among participants who self-identified as Asian, non-Hispanic Black, or other or multiple races (vs non-Hispanic White) ( P  = .003 for interaction) and among participants self-rated with low (vs high) socioeconomic status ( P  < .001 for interaction). Within a subset of 9865 participants with data on BMI at menarche, exploratory mediation analysis estimated that 46% (95% CI, 35%-61%) of the temporal trend in age at menarche was explained by BMI.

Conclusions and Relevance   In this cohort study of 71 341 individuals in the US, as birth year increased, mean age at menarche decreased and time to regularity increased. The trends were stronger among racial and ethnic minority groups and individuals of low self-rated socioeconomic status. These trends may contribute to the increase in adverse health outcomes and disparities in the US.

Menarche is the culmination of a complex sequence of events involving the maturation of the reproductive axis. 1 , 2 Early menarche is associated with increased risk of adverse health outcomes, such as cardiovascular diseases, cancers, spontaneous abortion, and premature death, 3 - 9 whereas late menarche is associated with increased risk of fractures. 10 , 11 Studies have found trends toward earlier menarche during the past 5 to 10 decades in the US as well as globally. 12 - 19 In the US, studies have additionally evaluated whether this trend varied by sociodemographic factors. 13 , 20 - 26 Some of them 13 , 21 - 23 , 25 showed significant racial and ethnic differences, whereas others 20 , 24 , 26 did not, and most 13 , 20 , 22 , 24 were limited to non-Hispanic Black vs White comparisons. Furthermore, most studies 20 , 21 , 23 , 24 , 26 focused on mean age at menarche, with the frequency of early or late menarche rarely evaluated. Notably, obesity is a risk factor for early-onset puberty, 27 - 31 and the prevalence of childhood obesity has increased in the US, 32 , 33 leading to hypotheses on the potential role of obesity in the trends toward earlier menarche. However, whether obesity is the primary factor underlying the trends in menarche remains debatable. 34 Whether and to what extent the trend in menarche is attributable to changes in early-life body mass index (BMI) remains to be determined. 28

The menstrual cycle is a vital sign. 35 The maturation of the reproductive axis, measured as the time from menarche to established cycle regularity, is another important but understudied hallmark of early-life menstrual health. Within 1 to 2 years after menarche, irregular cycles are considered a normal process of pubertal transition. 36 , 37 Full maturation of the reproductive axis leads to more regular menstrual function. 38 Longer time to regularity has been associated with lower fecundability, longer menstrual cycles, and increased risk of metabolic conditions and all-cause mortality. 39 - 42 Whereas the trends in time to regularity (influenced by environmental pollutants) 43 , 44 were evaluated in Japanese 14 and French 45 cohorts, it is not known whether it has also changed during the past several decades in the US.

In this study, we used data from a large, mobile application–based cohort of adults in the US to evaluate temporal trends in menarche and time to regularity among members of a racially and ethnically diverse study population born between 1950 and 2005. We analyzed overall temporal trends and whether observed trends differ by sociodemographic factors. Additionally, we explored whether BMI at menarche might mediate the observed temporal trends.

The Apple Women’s Health Study is a prospective digital cohort study in the US. Users of the Apple Research app on their iPhone were eligible if they had ever menstruated at least once in life, live in the US, were at least 18 years old (19 years in Alabama and Nebraska and 21 years in Puerto Rico), and were able to communicate in English. Eligibility also required sole use of an iCloud account and an iPhone. Enrollment began on November 14, 2019, and is ongoing. Participants provided written informed consent at enrollment. This study was approved by the institutional review board at Advarra. Details were described previously. 46 On enrollment, participants were asked to complete surveys of demographics as well as reproductive and medical history. For this analysis, we included participants who reported female sex assigned at birth, who were enrolled until March 20, 2023, and who provided age at menarche information. We excluded those born in 1931 to 1949 due to potential survival bias and too few individuals representing this group. A conceptual model is shown in eFigure 1 in Supplement 1 . The final study population included 71 341 participants; data analysis was limited to subsets who answered the relevant questions (eFigure 2 in Supplement 1 ). This study followed the Strengthening the Reporting of Observational Studies in Epidemiology ( STROBE ) guideline.

We grouped self-reported year of birth as 1950 to 1969 (n = 5223), 1970 to 1979 (n = 12 226), 1980 to 1989 (n = 22 086), 1990 to 1999 (n = 23 894), and 2000 to 2005 (n = 7912). Participants were asked the question, “ At what age did you have your first menstrual period? It’s okay to estimate,” with the following response options: “7 years old or younger,” integer options between 8 and 15 years old, “16 years old or older,” “I don’t know,” or “I prefer not to answer.” Those who indicated they did not know or preferred not to answer or did not respond were excluded. We derived the following measures: (1) age at menarche (in years) (we assigned the value of 7 to those aged ≤7 years [196 (0.3%)] and the value of 16 to those aged ≥16 years [2447 (3.4%)]); (2) early menarche (yes/no) (age at menarche <11 years 47 ); (3) very early menarche (yes/no) (age at menarche <9 years 48 ); and (4) late menarche (yes/no) (age at menarche ≥16 years). 49

Participants were asked, “After your first menstrual cycle, how long did it take for your cycle to become regular?” with the following response options: “less than 1 year,” “1-2 years,” “3-4 years,” “more than 5 years,” “after using hormones (eg, birth control pills),” “They’re not yet regular,” “I don’t know,” or “I prefer not to answer.” Those who indicated don’t know or prefer not to answer or who did not respond were considered missing. We further excluded 224 individuals with potentially inaccurate time-to-regularity information (eMethods in Supplement 1 ). For the remaining 61 932 participants, we categorized time to regularity as 2 years or less, 3 to 4 years, more than 5 years, not yet regular, or regular after using hormones.

We considered the following self-reported variables to evaluate whether the temporal trends in age at menarche or time to regularity differ by sociodemographic factors: (1) self-identified race and ethnicity (Asian, Hispanic, non-Hispanic Black, non-Hispanic White, and other and multiple races (including American Indian or Alaska Native, Middle Eastern or North African, Native Hawaiian or other Pacific Islander, “None of these fully describe me,” and self-identified with >1 option) 50 ; (2) subjective socioeconomic status (SES) at enrollment based on the MacArthur Scale of Subjective Social Status 51 (categorized as 0-3 [low], 4-5 [medium], and 6-9 [high]), which was used as a surrogate for premenarche SES; and (3) geographic location (based on state of residence and categorized as Northeast, Midwest, South, and West).

In addition, among a subset of 9865 participants (13.8%) who retrospectively reported weight and height at menarche, we derived BMI (calculated as weight in kilograms divided by height in meters squared) for age z scores, percentiles, and categories at menarche using the Centers for Disease Control and Prevention Growth Chart. 52 - 54 We considered BMI at menarche as a potential mediator of temporal trends in age at menarche or time to regularity.

We calculated means (SDs) for continuous variables and reported numbers (percentages) for binary or categorical variables, overall and stratified by birth year categories (χ 2 tests were performed to identify differences in time to regularity by birth year categories). We summarized the percentages of time to regularity by age at menarche. We used generalized linear regression (gaussian or binomial distributions for continuous or binary categorical variables), with birth year as the exposure variable to generate P values for temporal trends.

To understand how temporal trends differ by sociodemographic factors, we performed analyses stratified by each covariate. A test of trend was performed within each level of the covariate by including birth year as the exposure variable in regression models. We also tested whether the slope of trends differed by covariates by including an interaction term between each covariate and birth year in the regression models and performing a type 3 test for significance.

We evaluated trends over time in the subset of 9865 participants with data on BMI at menarche. We performed an exploratory causal mediation analysis 55 , 56 with nonparametric bootstrap (500 simulations) to quantify the proportions (95% CIs) of temporal trends in menarche or time to regularity mediated by BMI z score at menarche. We evaluated these temporal trends as a secondary analysis after stratifying by BMI categories at menarche or adjusting for BMI at menarche z scores.

To evaluate the robustness of our results, we performed sensitivity analyses, including evaluating the temporal trends in time to regularity when further adjusted for age at menarche, using models that mutually adjusted for race and ethnicity and SES and using multinomial logistic models for the categorical time-to-regularity variable, with 2 years or less as the referent group. Analyses were conducted in Python, version 3.6 (Python Software Foundation) and R, version 4.1.2 (R Project for Statistical Computing). All statistical tests were 2-sided with 95% CIs. P  < .05 was considered statistically significant.

The Table shows the characteristics of the 71 341 participants. Among them, 2228 (3.1%) self-identified as Asian, 4918 (6.9%) as Hispanic, 3665 (5.1%) as non-Hispanic Black, 49 518 (69.4%) as non-Hispanic White, and 8461 (11.9%) as other or multiple races. A total of 21 561 (30.2%) had a high subjective SES level. The mean (SD) age at menarche was 12.2 (1.6) years, and 9174 (12.9%) had early menarche (aged <11 years). A total of 38 524 (62.2%) reached regularity within 2 years after menarche, whereas 6950 (11.2%) did not establish regularity. Characteristics of the 9865 participants with weight and height information at menarche are given in eTable 1 in Supplement 1 . Compared with the full study population, these participants tend to have earlier birth years, be non-Hispanic White, and have high subjective SES.

Figure 1 shows the temporal trends of age at menarche and time to regularity. The mean (SD) age at menarche decreased from 12.5 (1.6) to 11.9 (1.5) years comparing those born in 1950 to 1969 vs 2000 to 2005 ( P < .001 for trend) ( Figure 1 A and Table ). The number of individuals experiencing early menarche increased from 449 (8.6%) to 1223 (15.5%), the number of individuals experiencing very early menarche increased from 31 (0.6%) to 110 (1.4%) for very early menarche, and the number of individuals experiencing late menarche decreased from 286 (5.5%) to 137 (1.7%) ( P < .001 for trend) ( Figure 1 B and Table ). From the 1950 to 1969 birth years to the 2000 to 2005 birth years, the number reaching regularity within 2 years decreased from 3463 (76.3%) to 4075 (56.0%), and the number not yet in regular cycles increased from 153 (3.4%) to 1375 (18.9%) ( P < .001 for trend) ( Figure 1 C and Table ). The mean (SD) time to regularity among those who spontaneously established regularity increased from 1.27 to 1.40 years ( P < .001 for trend) ( Table ). eFigure 3 in Supplement 1 shows lower percentages of time to regularity less than 2 years among those with either early or late menarche (inverse U-shaped association). Further adjusting for age at menarche resulted in similar distributions of time to regularity (eFigure 4 in Supplement 1 ).

The temporal trends stratified by race and ethnicity are presented in Figure 2 (estimates in eTable 2 in Supplement 1 ). Participants who were Asian, Hispanic, non-Hispanic Black, or of other or multiple races or ethnicities had consistently earlier mean age at menarche than non-Hispanic White participants. All racial and ethnic groups had temporal trends toward earlier menarche ( P  < .001 for trend), but when compared with non-Hispanic White participants, the magnitude of decrease in mean age at menarche across birth year categories was larger among those self-identified as non-Hispanic Black, Asian, and other or multiple races or ethnicities ( P  = .003 for interaction). All racial and ethnic groups showed a decreasing proportion of time to regularity within 2 years and an increased proportion of not establishing regularity ( P  < .001 for trend) (eFigure 5 and eTable 2 in Supplement 1 ), although there was no interaction between race and ethnicity and birth year. The temporal trends stratified by SES are presented in Figure 3 (estimates in eTable 3 in Supplement 1 ). Compared with those with high SES, those with low SES had earlier menarche, lower proportion of time to regularity within 2 years (eFigure 6 in Supplement 2 ), and larger magnitude of decrease in age at menarche. The heterogeneity by race and ethnicity for the trend toward earlier menarche remained when further adjusted for SES and vice versa (eTable 4 in Supplement 1 ). There was no interaction between geographic region and birth year when adjusting for race and ethnicity (eTable 5 in Supplement 1 ).

Overall, using multinomial logistic regressions yielded P -for-trend values of <.001 for each category of time to regularity compared with ≤2 years. Among the 9865 participants who provided weight and height at menarche, the BMI z score, percentile, and prevalence of obesity increased across birth year categories (eFigure 7 and eTable 1 in Supplement 1 ). An exploratory mediation analysis showed that the proportion of the temporal trends toward earlier menarche mediated by BMI z score at menarche was 46% (95% CI, 35%-61%) ( Figure 4 ). When stratified by BMI categories at menarche, the healthy and underweight group still showed a trend toward earlier menarche (eTable 6 in Supplement 1 ). When adjusted for BMI z scores, a trend toward earlier menarche remained (eTable 6 in Supplement 1 ), as did heterogeneity by race and ethnicity (eFigure 8 in Supplement 1 ). There was no evidence of significant mediation by BMI at menarche for the temporal trends in time to regularity (eTable 7 in Supplement 1 ).

This cohort study of 71 341 participants born between 1950 and 2005 in the US found temporal trends toward earlier menarche (earlier mean age, higher percentage of early menarche, and lower percentage of late menarche) and longer time from menarche to cycle regularity (lower percentage of time to regularity within 2 years, higher percentage of time to regularity within 3-4 years, and higher percentage of not establishing regularity). These trends remained across all sociodemographic groups but were stronger among certain non-White (specifically, Asian, non-Hispanic Black, and other or multiple races or ethnicities) and low SES groups. In an exploratory analysis, BMI at menarche may explain a significantly large proportion of the temporal trends toward earlier menarche.

Our findings of a temporal trend toward earlier menarche are consistent with some US-based studies, with similar magnitude of changes. 12 , 13 , 16 Other studies indicated that age at menarche stabilized during the past 50 years, whereas evidence that the median decreased by 2.5 to 4 months in the past 25 years remains, 20 , 57 consistent with a change from 12.2 to 11.9 years of age for those born in 1980 to 1989 vs 2000 to 2005 in our study. Despite a relatively small magnitude of change in mean age, our study is among the first to show that the percentages of early and very early menarche have also increased by almost 2-fold across birth years from 1950 to 2005, raising concerns that more individuals may be vulnerable to adverse health outcomes related to early menarche. 3 - 6 Late menarche has decreased, which may have other health implications, such as the decreasing rates of fractures. 58 , 59

We found that non-Hispanic Black participants had consistently earlier mean age at menarche than White participants, also similar to prior US-based studies. 13 , 20 - 26 We also found that non-Hispanic Black participants had a larger magnitude of change toward earlier menarche across birth year categories compared with non-Hispanic White participants. Similarly, we found other groups (Asian and other or multiple races), rarely evaluated in previous studies of menarche, also had consistently earlier mean ages and larger magnitudes of change toward earlier menarche than non-Hispanic White participants. We found similar patterns for self-rated low SES (compared with high SES). The factors driving this widening gap of disparities remain to be explored; transethnic genome-wide association studies indicated that these disparities are unlikely to be attributed to genetic variations, suggesting they may be driven by other environmental or contextual factors that may, through racism, impact different pathways, leading to earlier menarche. 60

Onset of menarche is closely related to attainment of adequate body fat via pathways such as increased insulin-like growth factor 1 and leptin that stimulate gonadotropin-releasing hormone. 61 In our exploratory analysis, we found that BMI at menarche may explain 46% of the temporal trends in menarche. This finding suggests that childhood obesity, a risk factor for earlier puberty, 27 - 30 , 62 which has increased in the US, 32 , 33 could be a contributing factor to the trend toward earlier menarche. However, the remaining 54% remain unclear. Our exploratory analysis also showed that BMI may have contributed to earlier menarche among non-Hispanic White, Black, and other or multiple races, whereas the trend among Asian and Hispanic individuals remains to be further explored. Previous studies also showed that the biggest decrease in age at menarche occurred before the obesity epidemic in the US, 34 suggesting that other factors need to be explored to explain these trends and disparities, including environmental factors (eg, endocrine-disrupting chemicals, metals, or air pollutants could impact pubertal timing, 63 - 65 with disproportionally higher exposure among certain racial and ethnic minority groups), 66 - 68 dietary patterns (eg, sugar intake via insulin-mediated pathways), 69 - 71 psychosocial stress, 72 and adverse childhood experiences. 73

Our findings of temporal trends toward longer time to regularity and higher proportion of never establishing regularity in the US have not been previously reported. Because longer time to regularity has been associated with adverse outcomes, 39 - 42 it may serve as an early-life vital sign. These temporal trends may be driven by longer time to maturation of the reproductive axis (eg, impacted by endocrine disruptors) 74 or increasing ovulation disorders 75 that impact cycle regularity. Although earlier studies suggest that regular menstruation should be established within 1 to 2 years after menarche, 37 , 38 , 76 , 77 evidence remains limited on whether delays beyond 2 years warrant clinical or lifestyle intervention. 78 In our study, the mean time to regularity among those who spontaneously established regularity was 1.2 to 1.5 years within the 2-year window. However, the proportions taking 3 to 4 years or never establishing regularity were increasing. A French cohort born between 1935 and 1950 showed a decrease from 64% to 53% for time to regularity within 1 year, but data are limited for the US. 45 We also found differences by race and ethnicity (eg, Hispanic individuals reported a higher rate of not establishing regularity compared with their non-Hispanic White peers, consistent with a study 79 showing that Hispanic individuals having the highest risk of cycle irregularity in adulthood). Our findings suggest the necessity of further studies on the postmenarche years and the need for early intervention during relevant time windows. Continued research on the association of BMI and other factors on reproductive development is needed, and findings should be conveyed to health professionals.

This study has several unique strengths. First, a large study size of 71 341 participants in a heterogeneous population allowed for sufficient statistical power to detect racial and ethnic differences, even for groups that were previously understudied. Second, we evaluated temporal trends in the percentages of early or late menarche in addition to mean age. Third, our study is the first, to our knowledge, to evaluate and report a temporal trend toward longer time to regularity, suggesting future research directions on this understudied early-life marker of menstrual health. Fourth, our study is the first, to our knowledge, to use digital observational cohort data evaluating BMI at menarche as a potential contributor to the observed temporal trends.

Our study also has limitations. First, the retrospective self-report may induce recall bias and misclassification, likely differential across birth year categories. However, previous validation studies 80 - 82 showed moderate to high correlations between recalled and original age and body size at menarche. Second, BMI at menarche was only available among a subset of participants with demographic distributions different from the full study population. Third, data are limited for additional early-life factors that may contribute to these trends. Fourth, our results may not be generalizable to all US individuals who menstruate or to other populations. Potential selection bias may arise due to self-selection into the study that may be impacted by sociodemographic characteristics.

In this US cohort study of 71 341 individuals born between 1950 and 2005, we observed temporal trends toward earlier menarche and longer time to regularity. These trends appeared across all sociodemographic groups but were stronger among certain racial and ethnic groups (Asian, non-Hispanic Black, or other and multiple races or ethnicities) and low subjective SES groups. Body mass index at menarche mediated a significantly large proportion of the trends toward earlier menarche. Further awareness among health care practitioners and researchers is needed to understand the reasons for these trends and their health implications.

Accepted for Publication: March 1, 2024.

Published: May 29, 2024. doi:10.1001/jamanetworkopen.2024.12854

Open Access: This is an open access article distributed under the terms of the CC-BY-NC-ND License . © 2024 Wang Z et al. JAMA Network Open .

Corresponding Author: Zifan Wang, PhD, MS, Department of Environmental Health, Harvard T.H. Chan School of Public Health, 665 Huntington Ave, Bldg 1, Room 1404, Boston, MA 02115 ( [email protected] ).

Author Contributions: Dr Wang and Mr Asokan had full access to all of the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis. Dr Wang and Mr Asokan contributed equally to this work.

Concept and design: Wang, Jukic, Williams, Hauser, Coull, Mahalingaiah.

Acquisition, analysis, or interpretation of data: All authors.

Drafting of the manuscript: Wang, Asokan, Mahalingaiah.

Critical review of the manuscript for important intellectual content: Asokan, Onnela, Baird, Jukic, Wilcox, Curry, Fischer-Colbrie, Williams, Hauser, Coull, Mahalingaiah.

Statistical analysis: Wang, Asokan, Onnela, Coull, Mahalingaiah.

Obtained funding: Curry, Williams, Hauser, Coull, Mahalingaiah.

Administrative, technical, or material support: Asokan, Jukic, Wilcox, Curry, Fischer-Colbrie, Coull, Mahalingaiah.

Supervision: Hauser, Mahalingaiah.

Conflict of Interest Disclosures: Dr Curry and Mr Fischer-Colbrie are employed by Apple Inc and report owning Apple stocks. No other disclosures were reported.

Funding/Support: This research was supported in part by award Z01ES103333 from the Intramural Research Program of the National Institutes of Health (Drs Baird, Jukic, and Wilcox). Support for Drs Baird, Jukic, and Wilcox was provided by the Intramural Research Program of the National Institute of Environmental Health Sciences, National Institutes of Health. Apple Inc is the sponsor of this study.

Role of the Funder/Sponsor: Apple Inc provided platforms and software for the collection and management of the data and participated in the review and approval of the manuscript. It played no role in the design and conduct of the study, analysis and interpretation of the data, preparation of the manuscript, or in the decision to submit the manuscript for publication.

Meeting Presentation: Preliminary findings of this work were presented at the American Society for Reproductive Medicine Scientific Congress & Expo; October 16, 2023; New Orleans, Louisiana.

Data Sharing Statement: See Supplement 2 .

Additional Contributions: Malaika Gabra, BA, Mackenzie Collyer, BS, Elizabeth Peebles, BA, Carrie Sarcione, MEd, and Ariel Scalise, MPH, Harvard T.H. Chan School of Public Health, assisted with this study and are paid staff members of the Apple Women's Health Study (AWHS), who provided support on the administrative parts of this study. The AWHS team would like to thank the study participants for consenting and contributing to the advancement of women’s health research.

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• Volume 3, Issue 1
• Regular use of fish oil supplements and course of cardiovascular diseases: prospective cohort study
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• Ge Chen 1 ,
• Zhengmin (Min) Qian 2 ,
• Junguo Zhang 1 ,
• Shiyu Zhang 1 ,
• http://orcid.org/0000-0002-7003-6565 Zilong Zhang 1 ,
• Michael G Vaughn 3 ,
• Hannah E Aaron 2 ,
• Chuangshi Wang 4 ,
• Gregory YH Lip 5 , 6 and
• http://orcid.org/0000-0002-3643-9408 Hualiang Lin 1
• 1 Department of Epidemiology , Sun Yat-Sen University , Guangzhou , China
• 2 Department of Epidemiology and Biostatistics, College for Public Health and Social Justice , Saint Louis University , Saint Louis , Missouri , USA
• 3 School of Social Work, College for Public Health and Social Justice , Saint Louis University , Saint Louis , Missouri , USA
• 4 Medical Research and Biometrics Centre , Fuwai Hospital, National Centre for Cardiovascular Diseases, Peking Union Medical College , Beijing , China
• 5 Liverpool Centre for Cardiovascular Science , University of Liverpool and Liverpool Heart and Chest Hospital , Liverpool , UK
• 6 Department of Clinical Medicine , Aalborg University , Aalborg , Denmark
• Correspondence to Dr Hualiang Lin, Department of Epidemiology, Sun Yat-Sen University, Guangzhou, Guangdong 510080, China; linhualiang{at}mail.sysu.edu.cn

Objective To examine the effects of fish oil supplements on the clinical course of cardiovascular disease, from a healthy state to atrial fibrillation, major adverse cardiovascular events, and subsequently death.

Design Prospective cohort study.

Setting UK Biobank study, 1 January 2006 to 31 December 2010, with follow-up to 31 March 2021 (median follow-up 11.9 years).

Participants 415 737 participants, aged 40-69 years, enrolled in the UK Biobank study.

Main outcome measures Incident cases of atrial fibrillation, major adverse cardiovascular events, and death, identified by linkage to hospital inpatient records and death registries. Role of fish oil supplements in different progressive stages of cardiovascular diseases, from healthy status (primary stage), to atrial fibrillation (secondary stage), major adverse cardiovascular events (tertiary stage), and death (end stage).

Results Among 415 737 participants free of cardiovascular diseases, 18 367 patients with incident atrial fibrillation, 22 636 with major adverse cardiovascular events, and 22 140 deaths during follow-up were identified. Regular use of fish oil supplements had different roles in the transitions from healthy status to atrial fibrillation, to major adverse cardiovascular events, and then to death. For people without cardiovascular disease, hazard ratios were 1.13 (95% confidence interval 1.10 to 1.17) for the transition from healthy status to atrial fibrillation and 1.05 (1.00 to 1.11) from healthy status to stroke. For participants with a diagnosis of a known cardiovascular disease, regular use of fish oil supplements was beneficial for transitions from atrial fibrillation to major adverse cardiovascular events (hazard ratio 0.92, 0.87 to 0.98), atrial fibrillation to myocardial infarction (0.85, 0.76 to 0.96), and heart failure to death (0.91, 0.84 to 0.99).

Conclusions Regular use of fish oil supplements might be a risk factor for atrial fibrillation and stroke among the general population but could be beneficial for progression of cardiovascular disease from atrial fibrillation to major adverse cardiovascular events, and from atrial fibrillation to death. Further studies are needed to determine the precise mechanisms for the development and prognosis of cardiovascular disease events with regular use of fish oil supplements.

• Health policy
• Nutritional sciences
• Public health

Data availability statement

Data are available upon reasonable request. UK Biobank is an open access resource. Bona fide researchers can apply to use the UK Biobank dataset by registering and applying at http://ukbiobank.ac.uk/register-apply/ .

This is an open access article distributed in accordance with the Creative Commons Attribution 4.0 Unported (CC BY 4.0) license, which permits others to copy, redistribute, remix, transform and build upon this work for any purpose, provided the original work is properly cited, a link to the licence is given, and indication of whether changes were made. See:  https://creativecommons.org/licenses/by/4.0/ .

https://doi.org/10.1136/bmjmed-2022-000451

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WHAT IS ALREADY KNOWN ON THIS TOPIC

Findings of the effects of omega 3 fatty acids or fish oil on the risk of cardiovascular disease are controversial

Most previous studies focused on one health outcome and did not characterise specific cardiovascular disease outcomes (eg, atrial fibrillation, myocardial infarction, stroke, heart failure, and major adverse cardiovascular events)

Whether fish oil could differentially affect the dynamic course of cardiovascular diseases, from atrial fibrillation to major adverse cardiovascular events, to other specific cardiovascular disease outcomes, or even to death, is unclear

WHAT THIS STUDY ADDS

In people with no known cardiovascular disease, regular use of fish oil supplements was associated with an increased relative risk of atrial fibrillation and stroke

In people with known cardiovascular disease, the beneficial effects of fish oil supplements were seen on transitions from atrial fibrillation to major adverse cardiovascular events, atrial fibrillation to myocardial infarction, and heart failure to death

HOW THIS STUDY MIGHT AFFECT RESEARCH, PRACTICE, OR POLICY

Regular use of fish oil supplements might have different roles in the progression of cardiovascular disease

Further studies are needed to determine the precise mechanisms for the development and prognosis of cardiovascular disease events with regular use of fish oil supplements

Introduction

Cardiovascular disease is the leading cause of death worldwide, accounting for about one sixth of overall mortality in the UK. 1 2 Fish oil, a rich source of omega 3 fatty acids, containing eicosapentaenoic acid and docosahexaenoic acid, has been recommended as a dietary measure to prevent cardiovascular disease. 3 The UK National Institute for Health and Care Excellence recommends that people with or at high risk of cardiovascular disease consume at least one portion of oily fish a week, and the use of fish oil supplements has become popular in the UK and other western countries in recent years. 4 5

Although some epidemiological and clinical studies have assessed the effect of omega 3 fatty acids or fish oil on cardiovascular disease and its risk factors, the findings are controversial. The Agency for Healthcare Research and Quality systematically reviewed 37 observational studies and 61 randomised controlled trials, and found evidence indicating the beneficial effects of higher consumption of fish oil supplements on ischaemic stroke, whereas no beneficial effect was found for atrial fibrillation, major adverse cardiovascular events, myocardial infarction, total stroke, or all cause death. 6 In contrast, the Reduction of Cardiovascular Events with Icosapent Ethyl-Intervention Trial (REDUCE-IT) reported a decreased risk of major adverse cardiovascular events with icosapent ethyl in patients with raised levels of triglycerides, regardless of the use of statins. 7 Most of these findings, however, tended to assess the role of fish oil at a certain stage of cardiovascular disease. For example, some studies restricted the study population to people with a specific cardiovascular disease or at a high risk of cardiovascular disease, 8 9 whereas others evaluated databases of generally healthy populations. 10 All of these factors might preclude direct comparison of the effects of omega 3 fatty acids on atrial fibrillation events or on further deterioration of cardiovascular disease. Few studies have fully characterised specific cardiovascular disease outcomes or accounted for differential effects based on the complex disease characteristics of participants. Hence, in this study, we hypothesised that fish oil supplements might have harmful, beneficial, or no effect on different cardiovascular disease events in patients with varying health conditions.

Most previous studies on the association between fish oil and cardiovascular diseases generally focused on one health outcome. Also, no study highlighted the dynamic progressive course of cardiovascular diseases, from healthy status (primary stage), to atrial fibrillation (secondary stage), major adverse cardiovascular events (tertiary stage), and death (end stage). Clarifying this complex pathway in relation to the detailed progression of cardiovascular diseases would provide substantial insights into the prevention or treatment of future disease at critical stages. Whether fish oil could differentially affect the dynamic course of cardiovascular disease (ie, from atrial fibrillation to major adverse cardiovascular events, to other specific cardiovascular disease outcomes, or even to death) is unclear.

To deal with this evidence gap, we conducted a longitudinal cohort study to estimate the associations between fish oil supplements and specific clinical cardiovascular disease outcomes, including atrial fibrillation, major adverse cardiovascular events, and all cause death in people with no known cardiovascular disease or at high risk of cardiovascular disease for the purpose of primary prevention. We also assessed the modifying effects of fish oil supplements on the disease process, from atrial fibrillation to other outcomes, in people with known cardiovascular disease for the purpose of secondary prevention.

The UK Biobank is a community based cohort study with more than half a million UK inhabitants aged 40-69 years at recruitment. 11–13 Participants were invited to participate in this study if they were registered with the NHS and lived within 35 km of one of 22 Biobank assessment centres. Between 1 March 2006 and 31 July 2010, a baseline survey was conducted, based on a touch screen questionnaire and face-to-face interviews, to collect detailed personal, socioeconomic, and lifestyle characteristics, and information on diseases. 11–13

We excluded patients who had a diagnosis of atrial fibrillation (n=8326), heart failure (n=2748), myocardial infarction (n=11 949), stroke (n=7943), or cancer (n=48 624) at baseline; who withdrew from the study during follow-up (n=1299); or who had incomplete or outlier data for the main information (n=11 748). Because we focused only on a specific sequence of progression of cardiovascular disease (ie, from healthy status to atrial fibrillation, to major adverse cardiovascular events, and then to death), we excluded 1983 participants with other transition patterns. The remaining 415 737 participants were included in this analysis ( figure 1 ).

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Flowchart of selection of participants in study. The count of diagnosed diseases does not equate to the total number of individuals, because each person could have multiple diagnoses

Determining use of fish oil supplements

Information on regular use of fish oil supplements was collected from a self-reported touchscreen questionnaire during the baseline survey. 14 15 Each participant was asked whether they regularly used any fish oil supplement. Trained staff conducted a verbal interview with participants, asking if they were currently receiving treatments or taking any medicines, including omega 3 or fish oil supplements. Based on this information, we classified participants as regular users of fish oil supplements and non-users.

Follow-up and outcomes

Participants were followed up from the time of recruitment to death, loss to follow-up, or the end date of follow-up (31 March 2021), whichever came first. Incident cases of interest, including atrial fibrillation, heart failure, stroke, and myocardial infarction, were identified by linkage to death registries, primary care records, and hospital inpatient records. 11 Information on deaths was obtained from death registries of the NHS Information Centre, for participants in England and Wales, and from the NHS Central Register Scotland, for participants in Scotland. 11 Outcomes were defined by a three character ICD-10 (international classification of diseases, 10th revision) code. In this study, atrial fibrillation was defined by ICD-10 code I48, and major adverse cardiovascular events was determined by a combination of heart failure (I50, I11.0, I13.0, and I13.2), stroke (I60-I64), and myocardial infarction (I21, I22, I23, I24.1, and I25.2) codes.

We collected baseline data on age (<65 years and ≥65 years), sex (men and women), ethnic group (white and non-white), Townsend deprivation index (with a higher score indicating higher levels of deprivation), smoking status (never, previous, and current smokers), and alcohol consumption (never, previous, and current drinkers). Data for sex were taken from information in UK Biobank rather than from patient reported gender. Baseline dietary data were obtained from a dietary questionnaire completed by the patient or by an interviewer. The questionnaire was established for each nation (ie, England, Scotland, and Wales) to assess an individual's usual food intake (oily fish, non-oily fish, vegetables, fruit, and red meat). Diabetes mellitus was defined by ICD-10 codes E10-E14, self-reported physician's diagnosis, self-reported use of antidiabetic drugs, or haemoglobin A1c level ≥6.5% at baseline. Hypertension was defined by ICD-10 code I10 or I15, self-reported physician's diagnosis, self-reported use of antihypertensive drugs, or measured systolic and diastolic blood pressure ≥130/85 mm Hg at baseline. Information on other comorbidities (obesity (ICD-10 code E66), chronic obstructive pulmonary disease (J44), and chronic renal failure (N18)) was extracted from the first occurrence (UKB category ID 1712). Information on the use of drugs, including antihypertensive drugs, antidiabetic drug, and statins, was extracted from treatment and drug use records. Biochemistry markers were measured immediately at the central laboratory from serum samples collected at baseline. Binge drinking was defined as consumption of ≥6 standard drinks/day for women or ≥8 standard drinks/day for men. Detailed information on alcohol consumption and binge drinking in the UK Biobank was reported previously. 16

Statistical analysis

Characteristics of participants are summarised as number (percentages) for categorical variables and mean (standard deviation (SD)) for continuous variables. Comparisons between regular users of fish oil supplements and non-users were made with the χ 2 test or Student's t test.

We used a multi-state regression model to assess the role of regular use of fish oil supplements in the temporal disease progression from healthy status to atrial fibrillation, to major adverse cardiovascular events, and subsequently to death. The multi-state model is an extension of competing risks survival analysis. 17–19 The model allows simultaneous estimation of the role of risk factors in transitions from a healthy state to atrial fibrillation (transition A), healthy state to major adverse cardiovascular events (transition B), healthy state to death (transition C), atrial fibrillation to major adverse cardiovascular events (transition D), atrial fibrillation to death (transition E), and major adverse cardiovascular events to death (transition F) (transition pattern I, figure 2 ). The focus on these six transitions rather than on all possible health state transitions was preplanned and evidence based. If participants entered different states on the same date, we used the date of the theoretically previous state as the entry date of the latter state minus 0.5 days.

Numbers of participants in transition pattern I, from baseline to atrial fibrillation, major adverse cardiovascular events, and death

We further examined the effects of regular use of fish oil supplements on other pathways. For example, we divided major adverse cardiovascular events into three individual diseases (heart failure, stroke, and myocardial infarction), resulting in three independent pathways (transition patterns II, III, and IV, online supplemental figures S1–S3 ). All models were adjusted for age, sex, ethnic group, Townsend deprivation index, consumption of oily fish, consumption of non-oily fish, smoking status, alcohol consumption, obesity, hypertension, diabetes mellitus, chronic obstructive pulmonary disease, chronic renal failure, and use of statins, antidiabetic drugs, and antihypertensive drugs.

Supplemental material

We conducted several sensitivity analyses for the multi-state analyses of transition pattern A: additionally adjusting for setting (urban and rural), body mass index (underweight, normal, overweight, and obese), and physical activity (low, moderate, and high) in the model; adjusting for binge drinking rather than alcohol consumption; additionally adjusting for other variables of dietary intake (consumption of vegetables, fruit, and red meat); calculating participants' entry date into the previous state with different time intervals (0.5 years, one year, and two years); excluding participants who entered different states on the same date; excluding events occurring in the first two years of follow-up; restricting the follow-up date to 31 March 2020 to evaluate the influence of the covid-19 pandemic; and the use of the inverse probability weighted method to deal with biases between the regular users and non-users of fish oil supplements. Also, we conducted grouped analyses for sex, age group, ethnic group, smoking status, consumption of oily fish, consumption of non-oily fish, hypertension, and drug use, to examine effect modification. The interactions were tested with the likelihood ratio test. All analyses were carried out with R software (version 4.0.3), and the multi-model analysis was performed with the mstate package. A two tailed P value <0.05 was considered significant.

Patient and public involvement

Patients and/or the public were not involved in the design, or conduct, or reporting, or dissemination plans of this research. Participants were involved in developing the ethics and governance framework for UK Biobank and have been engaged in the progress of UK Biobank through follow-up questionnaires and additional assessment visits. UK Biobank keeps participants informed of all research output through the study website ( https://www.ukbiobank.ac.uk/explore-your-participation ), participant events, and newsletters.

A total of 415 737 participants (mean age 55.9 (SD 8.1) years; 55% women), aged 40-69 years, were analysed, and 31.4% (n=1 30 365) of participants reported regular use of fish oil supplements at baseline ( figure 1 ). Table 1 shows the characteristics of regular users (n=130 365) and non-users (n=285 372) of fish oil supplements. In the group of regular users of fish oil supplements, we found higher proportions of elderly people (22.6% v 13.9%), white people (95.1% v 94.2%), and women (57.6% v 53.9%), and higher consumption of alcohol (93.1% v 92.0%), oily fish (22.1% v 15.4%), and non-oily fish (18.0% v 15.4%) than non-users. The Townsend deprivation index (mean −1.5 (SD 3.0) v −1.3 (3.0)) and the proportion of current smokers (8.1% v 11.4%) were lower in regular users of fish oil supplements. Online supplemental table S1 provides more details on patient characteristics and online supplemental table S2 compares the basic characteristics of included and excluded people.

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Baseline characteristics of study participants grouped by use of fish oil supplements

Over a median follow-up time of of 11.9 years, 18 367 participants had atrial fibrillation (transition A) and 17 826 participants had major adverse cardiovascular events (transition B); 14 902 participants died without having atrial fibrillation or major adverse cardiovascular events (transition C). Among patients with incident atrial fibrillation, 4810 developed major adverse cardiovascular events (transition D) and 1653 died (transition E). Among patients with incident major adverse cardiovascular events, 5585 died during follow-up (transition F, figure 2 ). In separate analyses for individual diseases (transition patterns II, III, and IV, online supplemental figures S1–S3 ), in patients with atrial fibrillation, 3085 developed heart failure, 1180 had a stroke, and 1415 had a myocardial infarction. During follow-up, 2436, 2088, and 2098 deaths occurred in patients with heart failure, stroke, and myocardial infarction, respectively.

Multi-state regression results

Table 2 shows the different roles of regular use of fish oil supplements in transitions from healthy status to atrial fibrillation, to major adverse cardiovascular events, and then to death. For individuals in the primary stage (healthy status), we found that the use of fish oil supplements had a harmful effect on the transition from health to atrial fibrillation, with an adjusted hazard ratio of 1.13 (95% CI 1.10 to 1.17, transition A). The hazard ratio for transition B (from health to major adverse cardiovascular events) was 1.00 (95% CI 0.97 to 1.04) and for transition C (from health to death) was 0.98 (0.95 to 1.02).

Hazard ratios (95% confidence intervals) for each transition, for different transition patterns for progressive cardiovascular disease by regular use of fish oil supplements

For individuals in the secondary stage (atrial fibrillation) at the beginning of the study, regular use of fish oil supplements decreased the risk of major adverse cardiovascular events (transition D, hazard ratio 0.92, 95% CI 0.87 to 0.98), and had a borderline protective effect on the transition from atrial fibrillation to death (transition E, 0.91, 0.82 to 1.01). For transition F, from major adverse cardiovascular events to death, after adjusting for covariates, the hazard ratio was 0.99 (0.94 to 1.06, transition pattern I, table 2 ).

We divided major adverse cardiovascular events into three individual diseases (ie, heart failure, stroke, and myocardial infarction) and found that regular use of fish oil supplements was marginally associated with an increased risk of stroke in people with a healthy cardiovascular state (hazard ratio 1.05, 95% CI 1.00 to 1.11), whereas a protective effect was found in transitions from healthy cardiovascular states to heart failure (0.92, 0.86 to 0.98). For patients with atrial fibrillation, we found that the beneficial effects of regular use of fish oil supplements were for transitions from atrial fibrillation to myocardial infarction (0.85, 0.76 to 0.96), and from atrial fibrillation to death (0.88, 0.81 to 0.95) for transition pattern IV. For patients with heart failure, we found a protective effect of regular use of fish oil supplements on the risk of mortality (0.91, 0.84 to 0.99) (transition patterns II, III, and IV, table 2 ).

Stratified and sensitivity analyses

We found that age, sex, smoking, consumption of non-oily fish, prevalent hypertension, and use of statins and antihypertensive drugs modified the associations between regular use of fish oil supplements and the transition from healthy states to atrial fibrillation ( online supplemental figure S4 ). We found that the association between regular use of fish oil supplements and risk of transition from healthy states to major adverse cardiovascular events was greater in women (hazard ratio 1.06, 95% CI 1.00 to 1.11, P value for interaction=0.005) and non-smoking participants (1.06, 1.06 to 1.11, P value for interaction=0.001) ( online supplemental figure S4 ). The protective effect of regular use of fish oil supplements on the transition from healthy states to death was greater in men (hazard ratio 0.93, 95% CI 0.89 to 0.98, P value for interaction=0.003) and older participants (0.91, 0.86 to o 0.96, P value for interaction=0.002) ( online supplemental figures S5 and S6 ). The results were not substantially changed in the sensitivity analyses ( online supplemental table S3 ).

Principal findings

Our study characterised the regular use of fish oil supplements on the progressive course of cardiovascular disease, from a healthy state (primary stage), to atrial fibrillation (secondary stage), major adverse cardiovascular events (tertiary stage), and death (end stage). In this prospective analysis of more than 400 000 UK adults, we found that regular use of fish oil supplements could have a differential role in the progression of cardiovascular disease. For people with a healthy cardiovascular profile, regular use of fish oil supplements, a choice of primary prevention, was associated with an increased risk of atrial fibrillation. For participants with a diagnosis of atrial fibrillation, however, regular use of fish oil supplements, as secondary prevention, had a protective effect or no effect on transitions from atrial fibrillation to major adverse cardiovascular events, atrial fibrillation to death, and major adverse cardiovascular events to death. When we divided major adverse cardiovascular events into three individual diseases (ie, heart failure, stroke, and myocardial infarction), we found associations that could suggest a mildly harmful effect between regular use of fish oil supplements and transitions from a healthy cardiovascular state to stroke, whereas potential beneficial associations were found between regular use of fish oil supplements and transitions from atrial fibrillation to myocardial infarction, atrial fibrillation to death, and heart failure to death.

Comparison with other studies

Primary prevention.

The cardiovascular benefits of regular use of fish oil supplements have been examined in numerous studies but the results are controversial. Extending previous reports, our study estimated the associations between regular use of fish oil supplements and specific clinical cardiovascular disease outcomes in people with no known cardiovascular disease. Our findings are in agreement with the results of several previous randomised controlled trials and meta-analyses. The Long-Term Outcomes Study to Assess Statin Residual Risk with Epanova in High Cardiovascular Risk Patients with Hypertriglyceridaemia (STRENGTH) reported that consumption of 4 g/day of marine omega 3 fatty acids was associated with a 69% higher risk of new onset atrial fibrillation in people at high risk of cardiovascular disease. 20 A meta-analysis of seven randomised controlled trials showed that users of marine omega 3 fatty acids supplements had a higher risk of atrial fibrillation events, with a hazard ratio of 1.25 (95% CI 1.07 to 1.46, P=0.013). 21 The Vitamin D and Omega-3 Trial (VITAL Rhythm study), a large trial of omega 3 fatty acids for the primary prevention of cardiovascular disease in adults aged ≥50 years, however, found no effects on incident atrial fibrillation, major adverse cardiovascular events, or cardiovascular disease mortality among those treated with 840 mg/day of marine omega 3 fatty acids compared with placebo. 10 22

One possible explanation for the inconsistent results in these studies is that adverse effects might be related to dose and composition. Higher doses of omega 3 fatty acids used in previous studies might have had an important role in causing an adverse effect on atrial fibrillation. 21 One study found that high concentrations of fish oil altered cell membrane properties and inhibited Na-K-ATPase pump activity, whereas a low concentration of fish oil minimised peroxidation potential and optimised activity. 23 In another study, individuals with atrial fibrillation or flutter had higher percentages of total polyunsaturated fatty acids, and n-3 and n-6 polyunsaturated fatty acids, on red blood cell membranes than healthy controls. 24

In terms of composition of omega 3 fatty acids, a recent meta-analysis showed that eicosapentaenoic acid alone can be more effective at reducing the risk of cardiovascular disease than the combined effect of eicosapentaenoic acid and docosahexaenoic acid. 25 Similar outcomes were reported in the INSPIRE study, which showed that higher levels of docosahexaenoic acid reduced the cardiovascular benefits of eicosapentaenoic acid when given as a combination. 26 Another possible explanation is that age, sex, ethnic group, smoking status, dietary patterns, and use of statins and antidiabetic drugs by participants might modify the effects of regular use of fish oil supplements on cardiovascular disease events. Despite these differences in risk estimates, our findings do not support the use of fish oil or omega 3 fatty acid supplements for the primary prevention of incident atrial fibrillation or other specific clinical cardiovascular disease events in generally healthy individuals. Caution might be warranted when fish oil supplements are used for primary prevention because of the uncertain cardiovascular benefits.

Secondary prevention

Our large scale cohort study assessed the role of regular use of fish oil supplements on the disease process, from atrial fibrillation to more serious cardiovascular disease stages, to death, in people with known cardiovascular disease. Contrary to the observations for primary prevention, we found associations that could suggest beneficial effects between regular use of fish oil supplements and most cardiovascular disease transitions. No associations were found between regular use of fish oil supplements and transitions from atrial fibrillation to death, or from major adverse cardiovascular events to death.

Consistent with our hypothesis, the Gruppo Italiano per lo Studio della Sopravvivenza nell'Infarto Miocardico (GISSI) Prevenzione study reported an association between administration of low dose prescriptions of n-3 polyunsaturated fatty acids and reduced cardiovascular events in patients with recent myocardial infarction. 27 A meta-analysis of 16 randomised controlled trials also reported a tendency towards a greater beneficial effect for secondary prevention in patients with cardiovascular disease. 28 Why patients with previous atrial fibrillation benefit is unclear. These findings indicate that triglyceride independent effects of omega 3 fatty acids might in part be responsible for the benefits in cardiovascular disease seen in previous trials. 29–31 No proven biological mechanism for this explanation exists, however, and the dose and formulation of omega 3 fatty acids used in clinical practice are not known.

For the disease process, from cardiovascular disease to death, our findings are consistent with the results of secondary prevention trials of omega 3 fatty acids, which have mostly shown a weak or neutral preventive effect in all cause mortality with oil fish supplements. The GISSI heart failure trial (GISSI-HF), conducted in 6975 patients with chronic heart failure, reported that supplemental omega 3 fatty acids reduced the risk of all cause mortality by 9% (hazard ratio 0.91, 95% CI 0.833 to 0.998, P=0.041). 32 Zelniker et al showed that omega 3 fatty acids were inversely associated with a lower incidence of sudden cardiac death in patients with non-ST segment elevation acute coronary syndrome. 33 A meta-analysis found that use of omega 3 supplements of ≤1 capsule/day was not associated with all cause mortality, but among participants with a risk of cardiovascular disease, taking a higher dose was associated with a reduction in cardiac death and sudden death. 28 Individuals who might benefit the most from fish oil or omega 3 fatty acid supplements are possibly more vulnerable individuals, such as those with previous cardiovascular diseases and those who can no longer live in the community. How fish oil supplements stop further deterioration of cardiovascular disease is unclear, but the theory that supplemental omega 3 fatty acids might protect the coronary artery is biologically plausible, suggesting that omega 3 fatty acids have anti-inflammatory and anti-hypertriglyceridaemia effects, contributing to a reduction in thrombosis and improvement in endothelial function. 34–41 Nevertheless, the effects of omega 3 fatty acids vary according to an individual's previous use of statins, which might partly explain the different effects of fish oil supplements in people with and without cardiovascular disease.

Many studies of omega 3 fatty acids, including large scale clinical trials and meta-analyses, have not produced entirely consistent results. 21 25 42 Our study mainly explored the varied potential effects of regular use of fish oil supplements on progression of cardiovascular disease, offering an initial overview of this ongoing discussion. Our findings suggest caution in the use of fish oil supplements for primary prevention because of the uncertain cardiovascular benefits and adverse effects. Further studies are needed to determine whether potential confounders modify the effects of oil fish supplements and the precise mechanisms related to the development and prognosis of cardiovascular disease events.

Strengths and limitations of this study

The strengths of our study were the large sample size, long follow-up period, which allowed us to analyse clinically diagnosed incident diseases, and complete data on health outcomes. Another strength was our analytical strategy. The multi-state model gives less biased estimates than the conventional Cox model, and distinguished the effect of regular use of fish oil supplements on each transition in the course of cardiovascular disease.

Our study had some limitations. Firstly, as an observational study, no causal relations can be drawn from our findings. Secondly, although we adjusted for multiple covariates, residual confounding could still exist. Thirdly, information on dose and formulation of the fish oil supplements was not available in this study, so we could not evaluate potential dose dependent effects or differentiate between the effects of different fish oil formulations. Fourthly, the use of hospital inpatient data for determining atrial fibrillation events could have excluded some events triggered by acute episodes, such as surgery, trauma, and similar conditions, resulting in underestimation of the true risk because undiagnosed atrial fibrillation is a common occurrence. 43 Fifthly, most of the participants in this study were from the white ethnic group and whether the findings can be generalised to other ethnic groups is not known. Finally, our study did not consider behavioural changes in populations with different cardiovascular profiles because of limited information, and variations in outcomes for different cardiovascular states merits further exploration.

Conclusions

This large scale prospective study of a UK cohort suggested that regular use of fish oil supplements might have differential roles in the course of cardiovascular diseases. Regular use of fish oil supplements might be a risk factor for atrial fibrillation and stroke among the general population but could be beneficial for disease progression, from atrial fibrillation to major adverse cardiovascular events, and from atrial fibrillation to death. Further studies are needed to determine whether potential confounders modify the effects of oil fish supplements and the precise mechanisms for the development and prognosis of cardiovascular disease events.

Ethics statements

Patient consent for publication.

Consent obtained directly from patients.

Ethics approval

The UK Biobank study obtained ethical approval from the North West Multicentre Research ethics committee, Information Advisory Group, and the Community Health Index Advisory Group (REC reference for UK Biobank 11/NW/0382). Participants gave informed consent to participate in the study before taking part.

Acknowledgments

This study was conducted with UK Biobank Resource (application No: 69550). We appreciate all participants and professionals contributing to UK Biobank.

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Supplementary materials

Supplementary data.

This web only file has been produced by the BMJ Publishing Group from an electronic file supplied by the author(s) and has not been edited for content.

• Data supplement 1
• Data supplement 2

GYL and HL are joint senior authors.

Contributors HL supervised the whole project and designed the work. GC and HL directly accessed and verified the underlying data reported in the manuscript. GC contributed to data interpretation and writing of the report. ZQ, SZ, JZ, ZZ, MGV, HEA, CW, and GYHL contributed to the discussion and data interpretation, and revised the manuscript. All authors had full access to all of the data in the study and had final responsibility for the decision to submit for publication. The corresponding author attests that all listed authors meet authorship criteria and that no others meeting the criteria have been omitted. HL is the guarantor. Transparency: The lead author (guarantor) affirms that the manuscript is an honest, accurate, and transparent account of the study being reported; that no important aspects of the study have been omitted; and that any discrepancies from the study as planned (and, if relevant, registered) have been explained.

Funding This work was supported by the Bill and Melinda Gates Foundation (grant No INV-016826). Under the grant conditions of the foundation, a creative commons attribution 4.0 generic license has already been assigned to the author accepted manuscript version that might arise from this submission. The funder had no role in considering the study design or in the collection, analysis, interpretation of data, writing of the report, or decision to submit the article for publication.

Competing interests All authors have completed the ICMJE uniform disclosure form at www.icmje.org/disclosure-of-interest/ and declare: support from Bill and Melinda Gates Foundation for the submitted work; no financial relationships with any organisations that might have an interest in the submitted work in the previous three years; no other relationships or activities that could appear to have influenced the submitted work.

Provenance and peer review Not commissioned; externally peer reviewed.

Supplemental material This content has been supplied by the author(s). It has not been vetted by BMJ Publishing Group Limited (BMJ) and may not have been peer-reviewed. Any opinions or recommendations discussed are solely those of the author(s) and are not endorsed by BMJ. BMJ disclaims all liability and responsibility arising from any reliance placed on the content. Where the content includes any translated material, BMJ does not warrant the accuracy and reliability of the translations (including but not limited to local regulations, clinical guidelines, terminology, drug names and drug dosages), and is not responsible for any error and/or omissions arising from translation and adaptation or otherwise.

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Google research shows the fast rise of AI-generated misinformation

Artificial intelligence has become a source of misinformation with lightning speed.

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From fake images of war to celebrity hoaxes, artificial intelligence technology has spawned new forms of reality-warping misinformation online. New analysis co-authored by Google researchers shows just how quickly the problem has grown.

The research, co-authored by researchers from Google, Duke University and several fact-checking and media organizations, was published in a preprint last week. The paper introduces a massive new dataset of misinformation going back to 1995 that was fact-checked by websites like Snopes.

According to the researchers, the data reveals that AI-generated images have quickly risen in prominence, becoming nearly as popular as more traditional forms of manipulation.

• Don't believe your eyes — fake photos have been a problem for a long time
• Analysis With rise of AI-generated images, distinguishing real from fake is about to get a lot harder

The work was first reported by 404 Media after being spotted by the Faked Up newsletter, and it clearly shows that "AI-generated images made up a minute proportion of content manipulations overall until early last year," the researchers wrote.

Last year saw the release of new AI image-generation tools by major players in tech, including OpenAI, Microsoft and Google itself. Now, AI-generated misinformation is "nearly as common as text and general content manipulations," the paper said.

The researchers note that the uptick in fact-checking AI images coincided with a general wave of AI hype, which may have led websites to focus on the technology. The dataset shows that fact-checking AI has slowed down in recent months, with traditional text and image manipulation seeing an increase.

The study looked at other forms of media, too, and found that video hoaxes now make up roughly 60 per cent of all fact-checked claims that include media.

That doesn't mean AI-generated misinformation has slowed down, said Sasha Luccioni, a leading AI ethics researcher at machine learning platform Hugging Face.

"Personally, I feel like this is because there are so many [examples of AI misinformation] that it's hard to keep track!" Luccioni said in an email. "I see them regularly myself, even outside of social media, in advertising, for instance."

• Explicit fake images of Taylor Swift prove laws haven't kept pace with tech, experts say
• Fake photos, but make it fashion. Why the Met Gala pics are just the beginning of AI deception

AI has been used to generate fake images of real people, with concerning effects. For example, fake nude images of Taylor Swift circulated earlier this year. 404 Media reported that the tool used to create the images was Microsoft's AI-generation software, which it licenses from ChatGPT maker OpenAI — prompting the tech giant to close a loophole allowing the images to be generated.

The technology has also fooled people in more innocuous ways. Recent fake photos showing Katy Perry attending the Met Gala in New York — in reality, she never did —  fooled observers on social media and even the star's own parents.

The rise of AI has caused headaches for social media companies and Google itself. Fake celebrity images have been featured prominently in Google image search results in the past, thanks to SEO-driven content farms. Using AI to manipulate search results is against Google's policies.

Taylor Swift deepfakes taken offline. It’s not so easy for regular people

Google spokespeople were not immediately available for comment. Previously, a spokesperson told technology news outlet Motherboard that "when we find instances where low-quality content is ranking highly, we build scalable solutions that improve the results not for just one search, but for a range of queries."

To deal with the problem of AI fakes, Google has launched such initiatives as digital waterma rking , which flags AI-generated images as fake with a mark that is invisible to the human eye. The company, along with Microsoft, Intel and Adobe, is also exploring giving creators the option to add a visible watermark to AI-generated images.

"I think if Big Tech companies collaborated on a standard of AI watermarks, that would definitely help the field as a whole at this point," Luccioni said.

ABOUT THE AUTHOR

Jordan Pearson is a Toronto-based journalist and the former executive editor of Motherboard.

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A new future of work: The race to deploy AI and raise skills in Europe and beyond

At a glance.

Amid tightening labor markets and a slowdown in productivity growth, Europe and the United States face shifts in labor demand, spurred by AI and automation. Our updated modeling of the future of work finds that demand for workers in STEM-related, healthcare, and other high-skill professions would rise, while demand for occupations such as office workers, production workers, and customer service representatives would decline. By 2030, in a midpoint adoption scenario, up to 30 percent of current hours worked could be automated, accelerated by generative AI (gen AI). Efforts to achieve net-zero emissions, an aging workforce, and growth in e-commerce, as well as infrastructure and technology spending and overall economic growth, could also shift employment demand.

By 2030, Europe could require up to 12 million occupational transitions, double the prepandemic pace. In the United States, required transitions could reach almost 12 million, in line with the prepandemic norm. Both regions navigated even higher levels of labor market shifts at the height of the COVID-19 period, suggesting that they can handle this scale of future job transitions. The pace of occupational change is broadly similar among countries in Europe, although the specific mix reflects their economic variations.

Businesses will need a major skills upgrade. Demand for technological and social and emotional skills could rise as demand for physical and manual and higher cognitive skills stabilizes. Surveyed executives in Europe and the United States expressed a need not only for advanced IT and data analytics but also for critical thinking, creativity, and teaching and training—skills they report as currently being in short supply. Companies plan to focus on retraining workers, more than hiring or subcontracting, to meet skill needs.

Workers with lower wages face challenges of redeployment as demand reweights toward occupations with higher wages in both Europe and the United States. Occupations with lower wages are likely to see reductions in demand, and workers will need to acquire new skills to transition to better-paying work. If that doesn’t happen, there is a risk of a more polarized labor market, with more higher-wage jobs than workers and too many workers for existing lower-wage jobs.

Choices made today could revive productivity growth while creating better societal outcomes. Embracing the path of accelerated technology adoption with proactive worker redeployment could help Europe achieve an annual productivity growth rate of up to 3 percent through 2030. However, slow adoption would limit that to 0.3 percent, closer to today’s level of productivity growth in Western Europe. Slow worker redeployment would leave millions unable to participate productively in the future of work.

Demand will change for a range of occupations through 2030, including growth in STEM- and healthcare-related occupations, among others

This report focuses on labor markets in nine major economies in the European Union along with the United Kingdom, in comparison with the United States. Technology, including most recently the rise of gen AI, along with other factors, will spur changes in the pattern of labor demand through 2030. Our study, which uses an updated version of the McKinsey Global Institute future of work model, seeks to quantify the occupational transitions that will be required and the changing nature of demand for different types of jobs and skills.

Our methodology

We used methodology consistent with other McKinsey Global Institute reports on the future of work to model trends of job changes at the level of occupations, activities, and skills. For this report, we focused our analysis on the 2022–30 period.

Our model estimates net changes in employment demand by sector and occupation; we also estimate occupational transitions, or the net number of workers that need to change in each type of occupation, based on which occupations face declining demand by 2030 relative to current employment in 2022. We included ten countries in Europe: nine EU members—the Czech Republic, Denmark, France, Germany, Italy, Netherlands, Poland, Spain, and Sweden—and the United Kingdom. For the United States, we build on estimates published in our 2023 report Generative AI and the future of work in America.

We included multiple drivers in our modeling: automation potential, net-zero transition, e-commerce growth, remote work adoption, increases in income, aging populations, technology investments, and infrastructure investments.

Two scenarios are used to bookend the work-automation model: “late” and “early.” For Europe, we modeled a “faster” scenario and a “slower” one. For the faster scenario, we use the midpoint—the arithmetical average between our late and early scenarios. For the slower scenario, we use a “mid late” trajectory, an arithmetical average between a late adoption scenario and the midpoint scenario. For the United States, we use the midpoint scenario, based on our earlier research.

We also estimate the productivity effects of automation, using GDP per full-time-equivalent (FTE) employee as the measure of productivity. We assumed that workers displaced by automation rejoin the workforce at 2022 productivity levels, net of automation, and in line with the expected 2030 occupational mix.

Amid tightening labor markets and a slowdown in productivity growth, Europe and the United States face shifts in labor demand, spurred not only by AI and automation but also by other trends, including efforts to achieve net-zero emissions, an aging population, infrastructure spending, technology investments, and growth in e-commerce, among others (see sidebar, “Our methodology”).

Our analysis finds that demand for occupations such as health professionals and other STEM-related professionals would grow by 17 to 30 percent between 2022 and 2030, (Exhibit 1).

By contrast, demand for workers in food services, production work, customer services, sales, and office support—all of which declined over the 2012–22 period—would continue to decline until 2030. These jobs involve a high share of repetitive tasks, data collection, and elementary data processing—all activities that automated systems can handle efficiently.

Up to 30 percent of hours worked could be automated by 2030, boosted by gen AI, leading to millions of required occupational transitions

By 2030, our analysis finds that about 27 percent of current hours worked in Europe and 30 percent of hours worked in the United States could be automated, accelerated by gen AI. Our model suggests that roughly 20 percent of hours worked could still be automated even without gen AI, implying a significant acceleration.

These trends will play out in labor markets in the form of workers needing to change occupations. By 2030, under the faster adoption scenario we modeled, Europe could require up to 12.0 million occupational transitions, affecting 6.5 percent of current employment. That is double the prepandemic pace (Exhibit 2). Under a slower scenario we modeled for Europe, the number of occupational transitions needed would amount to 8.5 million, affecting 4.6 percent of current employment. In the United States, required transitions could reach almost 12.0 million, affecting 7.5 percent of current employment. Unlike Europe, this magnitude of transitions is broadly in line with the prepandemic norm.

Both regions navigated even higher levels of labor market shifts at the height of the COVID-19 period. While these were abrupt and painful to many, given the forced nature of the shifts, the experience suggests that both regions have the ability to handle this scale of future job transitions.

Businesses will need a major skills upgrade

The occupational transitions noted above herald substantial shifts in workforce skills in a future in which automation and AI are integrated into the workplace (Exhibit 3). Workers use multiple skills to perform a given task, but for the purposes of our quantification, we identified the predominant skill used.

Demand for technological skills could see substantial growth in Europe and in the United States (increases of 25 percent and 29 percent, respectively, in hours worked by 2030 compared to 2022) under our midpoint scenario of automation adoption (which is the faster scenario for Europe).

Demand for social and emotional skills could rise by 11 percent in Europe and by 14 percent in the United States. Underlying this increase is higher demand for roles requiring interpersonal empathy and leadership skills. These skills are crucial in healthcare and managerial roles in an evolving economy that demands greater adaptability and flexibility.

Conversely, demand for work in which basic cognitive skills predominate is expected to decline by 14 percent. Basic cognitive skills are required primarily in office support or customer service roles, which are highly susceptible to being automated by AI. Among work characterized by these basic cognitive skills experiencing significant drops in demand are basic data processing and literacy, numeracy, and communication.

Demand for work in which higher cognitive skills predominate could also decline slightly, according to our analysis. While creativity is expected to remain highly sought after, with a potential increase of 12 percent by 2030, work activities characterized by other advanced cognitive skills such as advanced literacy and writing, along with quantitative and statistical skills, could decline by 19 percent.

Demand for physical and manual skills, on the other hand, could remain roughly level with the present. These skills remain the largest share of workforce skills, representing about 30 percent of total hours worked in 2022. Growth in demand for these skills between 2022 and 2030 could come from the build-out of infrastructure and higher investment in low-emissions sectors, while declines would be in line with continued automation in production work.

Business executives report skills shortages today and expect them to worsen

A survey we conducted of C-suite executives in five countries shows that companies are already grappling with skills challenges, including a skills mismatch, particularly in technological, higher cognitive, and social and emotional skills: about one-third of the more than 1,100 respondents report a shortfall in these critical areas. At the same time, a notable number of executives say they have enough employees with basic cognitive skills and, to a lesser extent, physical and manual skills.

Within technological skills, companies in our survey reported that their most significant shortages are in advanced IT skills and programming, advanced data analysis, and mathematical skills. Among higher cognitive skills, significant shortfalls are seen in critical thinking and problem structuring and in complex information processing. About 40 percent of the executives surveyed pointed to a shortage of workers with these skills, which are needed for working alongside new technologies (Exhibit 4).

Companies see retraining as key to acquiring needed skills and adapting to the new work landscape

Surveyed executives expect significant changes to their workforce skill levels and worry about not finding the right skills by 2030. More than one in four survey respondents said that failing to capture the needed skills could directly harm financial performance and indirectly impede their efforts to leverage the value from AI.

To acquire the skills they need, companies have three main options: retraining, hiring, and contracting workers. Our survey suggests that executives are looking at all three options, with retraining the most widely reported tactic planned to address the skills mismatch: on average, out of companies that mentioned retraining as one of their tactics to address skills mismatch, executives said they would retrain 32 percent of their workforce. The scale of retraining needs varies in degree. For example, respondents in the automotive industry expect 36 percent of their workforce to be retrained, compared with 28 percent in the financial services industry. Out of those who have mentioned hiring or contracting as their tactics to address the skills mismatch, executives surveyed said they would hire an average of 23 percent of their workforce and contract an average of 18 percent.

Occupational transitions will affect high-, medium-, and low-wage workers differently

All ten European countries we examined for this report may see increasing demand for top-earning occupations. By contrast, workers in the two lowest-wage-bracket occupations could be three to five times more likely to have to change occupations compared to the top wage earners, our analysis finds. The disparity is much higher in the United States, where workers in the two lowest-wage-bracket occupations are up to 14 times more likely to face occupational shifts than the highest earners. In Europe, the middle-wage population could be twice as affected by occupational transitions as the same population in United States, representing 7.3 percent of the working population who might face occupational transitions.

Enhancing human capital at the same time as deploying the technology rapidly could boost annual productivity growth

About quantumblack, ai by mckinsey.

QuantumBlack, McKinsey’s AI arm, helps companies transform using the power of technology, technical expertise, and industry experts. With thousands of practitioners at QuantumBlack (data engineers, data scientists, product managers, designers, and software engineers) and McKinsey (industry and domain experts), we are working to solve the world’s most important AI challenges. QuantumBlack Labs is our center of technology development and client innovation, which has been driving cutting-edge advancements and developments in AI through locations across the globe.

Organizations and policy makers have choices to make; the way they approach AI and automation, along with human capital augmentation, will affect economic and societal outcomes.

We have attempted to quantify at a high level the potential effects of different stances to AI deployment on productivity in Europe. Our analysis considers two dimensions. The first is the adoption rate of AI and automation technologies. We consider the faster scenario and the late scenario for technology adoption. Faster adoption would unlock greater productivity growth potential but also, potentially, more short-term labor disruption than the late scenario.

The second dimension we consider is the level of automated worker time that is redeployed into the economy. This represents the ability to redeploy the time gained by automation and productivity gains (for example, new tasks and job creation). This could vary depending on the success of worker training programs and strategies to match demand and supply in labor markets.

We based our analysis on two potential scenarios: either all displaced workers would be able to fully rejoin the economy at a similar productivity level as in 2022 or only some 80 percent of the automated workers’ time will be redeployed into the economy.

Exhibit 5 illustrates the various outcomes in terms of annual productivity growth rate. The top-right quadrant illustrates the highest economy-wide productivity, with an annual productivity growth rate of up to 3.1 percent. It requires fast adoption of technologies as well as full redeployment of displaced workers. The top-left quadrant also demonstrates technology adoption on a fast trajectory and shows a relatively high productivity growth rate (up to 2.5 percent). However, about 6.0 percent of total hours worked (equivalent to 10.2 million people not working) would not be redeployed in the economy. Finally, the two bottom quadrants depict the failure to adopt AI and automation, leading to limited productivity gains and translating into limited labor market disruptions.

Four priorities for companies

The adoption of automation technologies will be decisive in protecting businesses’ competitive advantage in an automation and AI era. To ensure successful deployment at a company level, business leaders can embrace four priorities.

Understand the potential. Leaders need to understand the potential of these technologies, notably including how AI and gen AI can augment and automate work. This includes estimating both the total capacity that these technologies could free up and their impact on role composition and skills requirements. Understanding this allows business leaders to frame their end-to-end strategy and adoption goals with regard to these technologies.

Plan a strategic workforce shift. Once they understand the potential of automation technologies, leaders need to plan the company’s shift toward readiness for the automation and AI era. This requires sizing the workforce and skill needs, based on strategically identified use cases, to assess the potential future talent gap. From this analysis will flow details about the extent of recruitment of new talent, upskilling, or reskilling of the current workforce that is needed, as well as where to redeploy freed capacity to more value-added tasks.

Prioritize people development. To ensure that the right talent is on hand to sustain the company strategy during all transformation phases, leaders could consider strengthening their capabilities to identify, attract, and recruit future AI and gen AI leaders in a tight market. They will also likely need to accelerate the building of AI and gen AI capabilities in the workforce. Nontechnical talent will also need training to adapt to the changing skills environment. Finally, leaders could deploy an HR strategy and operating model to fit the post–gen AI workforce.

Pursue the executive-education journey on automation technologies. Leaders also need to undertake their own education journey on automation technologies to maximize their contributions to their companies during the coming transformation. This includes empowering senior managers to explore automation technologies implications and subsequently role model to others, as well as bringing all company leaders together to create a dedicated road map to drive business and employee value.

AI and the toolbox of advanced new technologies are evolving at a breathtaking pace. For companies and policy makers, these technologies are highly compelling because they promise a range of benefits, including higher productivity, which could lift growth and prosperity. Yet, as this report has sought to illustrate, making full use of the advantages on offer will also require paying attention to the critical element of human capital. In the best-case scenario, workers’ skills will develop and adapt to new technological challenges. Achieving this goal in our new technological age will be highly challenging—but the benefits will be great.

Eric Hazan is a McKinsey senior partner based in Paris; Anu Madgavkar and Michael Chui are McKinsey Global Institute partners based in New Jersey and San Francisco, respectively; Sven Smit is chair of the McKinsey Global Institute and a McKinsey senior partner based in Amsterdam; Dana Maor is a McKinsey senior partner based in Tel Aviv; Gurneet Singh Dandona is an associate partner and a senior expert based in New York; and Roland Huyghues-Despointes is a consultant based in Paris.

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