Objective: To assess how information about adverse events is included in systematic reviews.
Study design and setting: We included all new Cochrane reviews published in the Cochrane Database of Systematic Reviews (CDSRs) and all new reviews (2003--2004) in the Database of Abstracts of Reviews of Effects (DAREs) in Issue 1 2005 of The Cochrane Library.
Results: More than half of Cochrane (44/78) and DARE (46/79) reviews assessed drug interventions. The rest assessed surgery (Cochrane [12]; DARE [10]), psychosocial, educational, or physiotherapy interventions (22; 23). Seventy-six percent (59/78) of Cochrane reviews mentioned adverse events as an outcome compared with 48% (38/79) of DARE reviews. Most reviews mentioning adverse events were of drug interventions (Cochrane [41/59]; DARE reviews [29/38]). Considering reviews that mentioned adverse events, 95% (56/59) of Cochrane reviews included only randomized trials and 73% (43/59) included an analysis of adverse events. For 10 Cochrane reviews, adverse events had not been reported by the included trials. In contrast, 58% (22/38) of DARE reviews mentioning adverse events included only randomized trials, the rest included both randomized and nonrandomized studies.
Conclusions: Most Cochrane reviews of drug interventions considered adverse events. This was not the case for DARE reviews and for Cochrane reviews of nondrug interventions. This could be improved.