Background: Previous systematic reviews have documented that funding of drug studies by drug companies is associated with findings favourable towards the sponsor’s product. However, meta-analyses of drug studies frequently fail to disclose the underlying funding of included studies or to investigate whether the source of funding influences results. To determine if funding bias should be taken into account in meta-analyses, it is important to know its extent. This study updates previous reviews showing the association of funding and research outcome to determine if the association persists and additionally investigates device studies.

Objectives: To investigate whether funding of drug or device studies by drug or device companies is associated with results and conclusions favourable to the sponsor. To investigate whether studies funded by drug or device companies differ in their risk of bias compared with studies with other sources of funding.

Methods: We searched major bibliographic databases, reference lists, previous systematic reviews and author files. Two reviewers included studies and final inclusion was by consensus of all authors. Two reviewers extracted data from included papers and assessed studies for risk of bias. Authors were contacted in order to obtain missing data. Data was analysed in RevMan.Results: We identified 2,579 studies in the search, 72 of which appeared to meet our inclusion criteria and were retained for final assessment by all authors. Sixty-three were published after the search period of our previous systematic review. Additional results will be presented at the Colloquium.

Conclusions: It appears that the evidence of funding bias has grown, but our conclusion awaits results from data analysis.