Objectives: To determine the extent to which reports of Cochrane reviews recommend the need for further research and, if so, the extent to which they make suggestions regarding that research.
Methods: We examined all 2535 reviews in Issue 4, 2005 of The Cochrane Library. Each review was categorized on the basis of whether a suggestion was included about specific interventions, participants, or outcome measures that should be included in future research. We also identified the frequency with which reviews conclude that no more research is needed or feasible, noted the need for further systematic reviewing, and refered to a relevant ongoing or planned study. We also report the number of studies listed in the 'Ongoing Studies' section in each review.
Results: Only 3.2% of reviews suggested explicitly that no more research is needed or feasible. In 82.0% of reviews, suggestions were made as to the specific interventions that need evaluating, in 30.2% the appropriate participants were suggested, and in 51.9% outcome measures were suggested. Suggestions for all three domains were made in 16.9% of the reviews. While 11.6% did not include a specific suggestion about any of these domains, 21.2% of reviews mention a relevant ongoing or planned study in one or both of the 'Implications for Research' and the 'Ongoing Studies' sections.
Conclusions: Most Cochrane reviews identify residual uncertainty and are a rich source of suggestions for further health-care research.