In a first, U.S. CDC retracts, replaces study about suicide risk in farmers

In a first for the CDC, the agency’s premier scientific publication has retracted a 2016 article on suicide, five months after a news story pointed out serious errors in the paper.

The article, initially published as “Suicide Rates by Occupational Group — 17 States, 2012,” had purported to find that farmers were at particularly high risk of suicide. That result in particular caught the attention of a website called The New Food Economy (TNFE), which last June called out what it said were errors in the CDC’s analysis. And on June 29, the journal, the Morbidity and Mortality Weekly Report (MMWR), issued a reader’s note.

As TNFE wrote, the crux of the mistake involves the misclassification of farmer suicides in a way that significantly inflated the rate of these events — errors the website said it first raised with the CDC in April 2018:

Under the federal occupational guidelines, farmers are classified as having a “management occupation,” not a “farming, fishing, and forestry occupation.” Yet it was the farming, fishing, and forestry, or “Triple-F,” occupational group that had the highest suicide rate in the country: 84.5 per 100,000 people, over 4 times the overall average of 20.3 among people in the workforce. The suicide rate among managers, in contrast, was exactly average.

The Triple-F category is made up of, as the name suggests, workers in agriculture, commercial fishing, hunting, and forestry. The emphasis is on “workers.” Managers, business owners, administrators, advisors, and other white-collar or entrepreneurial positions within these industries are generally categorized separately.

The CDC’s retraction notice, released today, acknowledges as much:

On July 1, 2016, MMWR published “Suicide Rates by Occupational Group — 17 States, 2012.”  On June 14, 2018, the authors informed MMWR about their concerns regarding the validity of some of the findings in the report, and on June 29, 2018, MMWR published “Notice to Readers: Ongoing Analysis of Suicide Rates Data by Occupational Group from Results Reported in MMWR.” The analysis is complete, and because the corrections change the conclusions, the original report is being retracted.

A new MMWR report, “Suicide Rates by Major Occupational Group — 17 States, 2012 and 2015,” will be published [November 15]. This report corrects inadvertent errors in the retracted report, uses updated methodology, includes authors from the National Institute for Occupational Safety and Health and additional authors from the National Center for Injury Prevention and Control, and provides analysis of both 2012 and 2015 National Violent Death Reporting System data. Corrected errors include the manual misclassification of some occupation codes in the earlier report (e.g., erroneous coding of farmers to the Farming, Fishing, and Forestry major occupational group instead of to the correct Management major occupational group), which led to errors in reporting of suicide numbers and rates in some groups.

In the new article, the triple F category ranks 8 and 9 in suicide rate, in 2012 and 2015, respectively. Construction and extraction workers rank number 1 in both years, up from number 2 in the erroneous analysis.   

A subanalysis in the new study found that farmers in the broader category of managers had a suicide rate of 44.9 per 100,000 in 2012 and 32 per 100,000 in 2015, which would be on par with construction workers. However, Deborah Stone, of the Division of Violence Prevention in CDC’s Injury Center, and one of the authors of both papers, said they did not compare those figures to other workers in the same category, so they are not making any comparisons:

Farmers are just a small subset of that major occupational group. It’s possible that other subsets would have been even higher.

Stone said the wholesale reworking of the article to correct the error and expand the years involved warranted adding authors from other agencies.

First retraction in more than 50 years of publishing

Charlotte Kent, the acting editor in chief of the MMWR, said the retraction was the first for MMWR since the agency began publishing the journal in 1961.

Because this was something new for us, we had a steep learning curve.

Kent said CDC spoke with retraction experts — not, in the interests of full disclosure yours truly — in order to make sure it handled the matter appropriately.

Once we had made a decision about which path we were going to take, then we came up with this path of retraction for errors that change things, and corrections for errors that didn’t.

The “corrections for errors that didn’t” includes a correction and republication of a 2016 paper on autism rates, which also appears today in MMWR.

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