A systematic review including 12 studies with a total of 12,238 subjects was abstracted in DARE. There were 5 cohort studies (n=5,416), 2 nested case-control studies (n=4,034) and 5 retrospective case control studies (n=2,788). Aspirin was associated with a reduced risk of prostate cancer. The pooled OR for total incidence of prostate cancer was 0.85 for prospective studies (95% confidence interval, CI: 0.77 to 0.94) and 1.01 for retrospective studies (95% CI: 0.86 to 1.18). Studies of mixtures of different NSAIDs had less consistent findings: OR 0.87 (95% CI: 0.61 to 1.23) for non-aspirin NSAIDs (heterogeneity P=0.005) and 0.67 (95% CI: 0.37 to 1.22) for mixture of aspirin and non-aspirin NSAIDs.