Adoption of the voluntary conflict of interest statement on PubMed

In 2017, the National Library of Medicine (NLM) added a voluntary field for conflict of interest (COI) statements ("posted COI") on the abstract page of PubMed, but the extent to which it is used is unknown. This repeated cross-sectional study examined journals and articles indexed on PubMed from 2016 through 2021. We described the proportion of all journals with at least one article that included a posted COI and the percentage of all articles that included a posted COI over time. We also examined 100 randomly selected articles published between June 2021 and May 2022 from each of the 40 highest impact journals. For these, we established whether the articles had published COIs, and, of these, the proportion that included a posted COI. Among approximately 7,000 journals publishing articles each year, the proportion of journals with at least one article with a posted COI statement increased from 25.9% in 2016 to 33.2% in 2021. Among nearly 400,000 articles published each year, the proportion of articles that included a posted COI also increased from 9.0% in 2016 to 43.0% in 2021. Among 3,888 articles published in the 40 highest impact journals in 2021-2022, 30.2% (95% CI: 28.7%-31.6%) had published COIs; of these, 63.3% (95% CI: 60.4%-66.0%) included a posted COI. Use of the PubMed COI statement has increased since it became available in 2017, but adoption is still limited, even among high impact journals. NLM should carry out additional outreach to journals that are not using the statement to promote greater transparency of COIs.