Adherence to data-sharing policies - a comparison of the BMJ with other major medical journals

Background: In 2024, the BMJ updated its data-sharing policy for clinical trials, requiring deidentified individual patient data (IPD) to be openly deposited prior to publication. Our objective was to discover if data-sharing increased after introduction of the new policy. Method: All data-sharing statements were downloaded from BMJ trials published in 2023 (submitted pre-updated policy) and 2025 (submitted post-updated policy). Data for 2025 were gathered for trials in five comparison medical journals. Data-sharing statements were coded to specify whether IPD were immediately available, and if not, the reason why. Where a statement gave a link to a repository, we checked whether data were available. Results: Openly available IPD for BMJ trials increased from 0/32 prior to the new policy to 19/33 (58%) after the updated policy; seven articles gave repository links that did not yield any data. In the five comparison journals, rates of open IPD varied from 0% to 5.6%. Conclusions: There was a substantial increase in open sharing of IPD after introduction of the new policy compared to a prior period. Open sharing of IPD is possible, but it is unpopular with authors and is unlikely to be achieved without firm editorial enforcement