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We investigated to which degree commercial funding is associated with estimated intervention effects in randomized trials. We included meta-epidemiological studies with published data on the association between commercial funding and results or conclusions of randomized trials. We searched five databases and other sources. We selected one result per meta-epidemiological study, preferably unadjusted ratio of odds ratios (ROR), for example, odds ratio(commercial funding)/odds ratio(noncommercial funding). We pooled RORs in random-effects meta-analyses (ROR <1 indicated exaggerated intervention effects in commercially funded trials), subgrouped (preplanned) by study aim: commercial funding per se versus risk of commercial funder influence. We included eight meta-epidemiological studies (264 meta-analyses, 2725 trials). The summary ROR was 0.95 (95% confidence interval 0.85-1.06). Subgroup analysis revealed a difference (p = 0.02) between studies of commercial funding per se, ROR 1.06 (0.95-1.17) and studies of risk of commercial funder influence, ROR 0.88 (0.79-0.97). In conclusion, we found no statistically significant association between commercial funding and estimated intervention effects when combining studies of commercial funding per se and studies of risk of commercial funder influence. A preplanned subgroup analysis indicated that trials with high risk of commercial funder influence exaggerated intervention effects by 12% (21%-3%), on average. Our results differ from previous theoretical considerations and findings from methodological studies and therefore call for confirmation. We suggest it is prudent to interpret results from commercially funded trials with caution, especially when there is a risk that the funder had direct influence on trial design, conduct, analysis, or reporting.

Randomised trials are often funded by commercial companies and methodological studies support a widely held suspicion that commercial funding may influence trial results and conclusions. However, these studies often have a risk of confounding and reporting bias. The risk of confounding is markedly reduced in meta-epidemiological studies that compare fairly similar trials within meta-analyses, and risk of reporting bias is reduced with access to unpublished data. Therefore, we initiated the COMmercial Funding In Trials (COMFIT) study aimed at investigating the impact of commercial funding on estimated intervention effects in randomised clinical trials based on a consortium of researchers who agreed to share meta-epidemiological study datasets with information on meta-analyses and trials included in meta-epidemiological studies. Here, we describe the COMFIT study, its database, and descriptive results. We included meta-epidemiological studies with published or unpublished data on trial funding source and results or conclusions. We searched five bibliographic databases and other sources. We invited authors of eligible meta-epidemiological studies to join the COMFIT consortium and to share data. The final construction of the COMFIT database involves checking data quality, identifying trial references, harmonising variable categories, and removing non-informative meta-analyses as well as correlated meta-analyses and trial results. We included data from 17 meta-epidemiological studies, covering 728 meta-analyses and 6841 trials. Seven studies (405 meta-analyses, 3272 trials) had not published analyses on the impact of commercial funding, but shared unpublished data on funding source. On this basis, we initiated the construction of a combined database. Once completed, the database will enable comprehensive analyses of the impact of commercial funding on trial results and conclusions with increased statistical power and a markedly reduced risk of confounding and reporting bias. [This article was written on behalf of the COMFIT Consortium.]

Background: Peer review may improve the quality of research manuscripts and aid in editorial decisions, but reviewers can have conflicts of interest that impact on their recommendations., Objectives: The objective was to systematically map and describe the extent and nature of empirical research on peer reviewers' conflicts of interest in biomedical research., Design: Scoping review METHODS: In this scoping review, we included studies investigating peer reviewers' conflicts of interest in journal manuscripts, theses and dissertations, conference abstracts, funding applications and clinical guidelines. We searched MEDLINE, Embase, The Cochrane Methodology Register, Google Scholar (up to January 2024) and other sources. Two authors independently included studies and extracted data on key study characteristics and results, and we organised data by study domain (eg, journal manuscripts) and study aims. We included studies directly investigating peer reviewers' conflicts of interest in our primary analysis, and studies investigating other questions (eg, reasons for retraction), but reporting relevant data on peer reviewers' conflicts of interest, were solely included in a supplementary analysis., Results: After screening 44 353 references, we included 71 studies, of which 41 were included in our primary analysis. The 41 studies were published between 2005 and 2023, and 34 (83%) were journal publications. 30 (73%) studies investigated journal manuscripts, 1 (2%) conference abstracts, 4 (10%) funding applications and 6 (15%) clinical guidelines. No studies investigated theses or dissertations. 37 (90%) studies used quantitative research methods, 2 (5%) qualitative and 2 (5%) mixed methods. 21 (51%) studies investigated both financial and non-financial interests, 6 (15%) solely financial interests, 5 (12%) solely non-financial interests and 9 (22%) did not report the type of interest. We organised included studies based on study aims, with some studies having multiple aims: impact on recommendations (one study), occurrence of peer reviewers' conflicts of interest (11 studies), stakeholders' experiences (13 studies) and policy and management (22 studies). One (2%) study investigated the impact of peer reviewers' personal connections with authors on reviewers' recommendations. Nine (22%) studies estimated prevalences of conflicts of interest among peer reviewers, ranging from 3%-91%. Two (5%) studies both reported that conflicts of interest were a reason for declining to review in 1% of cases. 13 (32%) studies investigated stakeholders' experiences with peer reviewers' conflicts of interest, primarily using questionnaires of reviewers, editors and researchers. 16 (39%) studies estimated prevalences of having conflict of interest policies for peer reviewers, ranging from 5%-96%, among journals, conferences and clinical guideline organisations. Finally, six (15%) studies estimated prevalences of public availabilities of reviewers' conflicts of interest declarations, ranging from 0%-71%., Conclusions: Most studies addressed conflicts of interest in peer review of journal manuscripts, primarily through surveys of journal policies or questionnaires of researchers, editors and peer reviewers. The impact of peer reviewers' conflicts of interest on recommendations and their prevalence is still poorly understood. Our results can guide future studies and be used to align policies and management of peer reviewers' conflicts of interest., Study Registration: Open Science Framework (DOI: 10.17605/OSF.IO/9QBMG)., Competing Interests: Competing interests: All authors have completed the ICMJE uniform disclosure form at https://www.icmje.org/disclosure-of-interest/ and declare support from The Independent Research Fund Denmark for the submitted work; LB is a Conflict of Interest Advisor for Health Canada, she receives consulting fees for her role as a Senior Research Integrity Editor at Cochrane, for which the University of Colorado receives remuneration, and she is unpaid member of the organising committee for the World Congress on Research Integrity. The authors declare no additional financial relationships with any organisations that might have an interest in the submitted work in the previous three years., (© Author(s) (or their employer(s)) 2025. No commercial re-use. See rights and permissions. Published by BMJ Group.)