[Conflict of interest in industry-funded medical research]

to assess the impact of the source of funding on the results of medical research.

review of systematic reviews on this subject.

relationship between source of funding and studies' conclusions.

twenty reviews of studies dealing with many different medical intervention were identified and included. The definitions of the source of funding varied largely across the studies and the information on funding available in the primary studies were generally judged as inaccurate and insufficient to identify the source. Some studies assessed the relationship between funding and methodological quality of the research and found no difference between industry funded and other studies. The majority of the studies included demonstrated the existence of a significant association between source of funding and results of the research showing that the studies financed by industry are more likely to conclude in favour of the intervention produced by the funding bodies. A meta-analysis was carried out on 18 of the twenty studies. Pooled Relative Risk was 1.58 (95% CI: 1.39 to 1.80) confirming the existence of a significant association and homogeneous results across different studies.

future reviews should seek for information regarding sources of funding of included studies and account for it in interpreting their results.