Unpublished systematic reviews and financial support: a meta-epidemiological study.

We identified 326 SRs registered in PROSPERO from February 2011 through February 2012. Among them, 85 SRs (26%) remained unpublished at least 65 months after registration. We found 241 published reports, including four conference abstracts and one poster presentation. Median time to publication from protocol registration was 16.3 months. Funding for SRs was associated with publication [odds ratio (OR) = 2.10; 95% confidence interval (CI) = 1.26 to 3.50]. We found no significant association of author-reported COIs with publication (OR = 2.35; 95% CI = 0.67 to 8.20). Twenty SRs were not published despite the authors reporting completion of the reviews in PROSPERO.