Conflicts of interest and industry funding declared in systematic reviews of interventions for six common diagnoses

There is a lack of data on the prevalence of conflicts of interest (COI) declared in systematic reviews over time. PubMed was searched for systematic reviews on interventions for chronic obstructive pulmonary disease, type 2 diabetes mellitus, hypertension, dementia, major depression, and osteoarthritis from 2010 and 2019. Selection was conducted by two independent authors, with disagreements resolved in consensus. COI and funding disclosures were extracted. COI were categorised using a specific framework. 746 systematic reviews were included. One third involved pharmacological interventions. Systematic reviews from China increased from 4% to 21% between 2010 and 2019; Cochrane reviews decreased from 19% to 4%. Systematic reviews presenting a COI statement increased from 79% to 94%. Those with at least one author declaring individual financial COI decreased from 22% to 17% but remained at 22–23% when excluding systematic reviews from China. Almost 1 in 3 systematic reviews on pharmacological interventions and invasive procedures declared individual financial COI for 2019. Individual intellectual COI were declared in 2.5% and other types of COI were very rare. Systematic reviews presenting a funding statement increased from 65% to 81%; industry funding decreased from 6% to 3.4%. Adding industry funding to the prevalence of systematic reviews declaring financial COI only made a marginal difference. The proportion of systematic reviews on interventions for common diagnoses declaring individual financial COI remained consistent at approximately one in five for both 2010 and 2019, underscoring the need for further research into the implications of this finding.