A new paper in the MDPI journal Publications reports that the only controlled study on the effect of giving COPD patients Omega-3 has been cited 52 times since being retracted. Of those, only two mentioned the retraction.
In 2005, Chest published an article that found that COPD patients who took omega-3 supplements for 2 years experienced improvements in their condition, such as better walking tests and a decrease in sputum cytokines. But when an institutional investigation found the lead author had falsified the data, the journal retracted the paper in 2008.
That’s news to many researchers in the field. Among the 50 papers that cited the research after 2008 without stating it had been retracted, 20 included “specific data” from the paper, while the other 30 “cited the reference in passing.” Articles citing the retracted study have themselves been cited 947 times total, pointing to the ripple effect this kind of unwitting mention can have throughout the literature.
These findings suggest that the retraction “was unsuccessfully communicated to the scientific community,” the authors note. On Chest’s site, the retracted article, “Effects of Omega-3 Polyunsaturated Fatty Acids on Inflammatory Markers in COPD” appears with a link to the retraction notice; PubMed also contains a note saying it is retracted.
The perpetuation of bad data is not just a problem for scientists, as the authors note. Googling “fish oil and COPD” (without quotes) brings up both news articles and pages on reference guides like WebMD and Everyday Health that reference the research without noting the retraction.
John Budd et al have been noting this problem since 1999, when they found that 92% of post-retraction citations failed to mention that the paper had been pulled.
The authors tap Retraction Watch as a useful resource, but until we get our database up and running, we aren’t a comprehensive stop for scientists checking their citations. They suggest both that journals make retractions very clear on the paper itself, and that scientists be more proactive in making sure they’re not citing retracted work.
Here’s the abstract for “Persistent Citation of the Only Published Randomised Controlled Trial of Omega-3 Supplementation in Chronic Obstructive Pulmonary Disease Six Years after Its Retraction”:
Scientific articles are retracted infrequently, yet have the potential to influence the scientific literature for years. The only randomised controlled trial to explore the effects of omega-3 polyunsaturated fatty acids in people with chronic obstructive pulmonary disease was retracted in 2008 due to falsified data. The objective of this research was to determine the frequency and nature of citations of this retracted paper. Web of Science and Google Scholar were used to determine the number of times the retracted article was cited. Citations were classified as either “retraction acknowledged” or “retraction not acknowledged”. The search was conducted on 6 August 2013 and updated on 25 March 2014. Results: The search resulted in 76 citations, of which 24 occurred prior to the retraction of the article. Of the 52 citations occurring after the retraction, only two acknowledged the retraction. Of the citations not acknowledging the retraction, 20 referred to specific data and 30 cited the reference in passing. This retracted article continues to be cited by authors, suggesting that information about the retraction was unsuccessfully communicated to the scientific community. Continual citation of retracted literature has the potential to bias a field of research and potentially misinform end-users.
Hat tip Rolf Degen.