Aspirin and risk of hemorrhagic stroke - A meta-analysis of randomized controlled trials

Context.-Aspirin has been widely used to prevent myocardial infarction and ischemic stroke but some studies have suggested it increases risk of hemorrhagic stroke. Objective-To estimate the risk of hemorrhagic stroke associated with aspirin treatment. Data Sources.-Studies were retrieved using MEDLINE (search terms, aspirin, cerebrovascular disorders, and stroke), bibliographies of the articles retrieved, and the authors' reference files. Study Selection.-All trials published in English-language journals before July 1997 in which participants were randomized to aspirin or a control treatment for at least 1 month and in which the incidence of stroke subtype was reported. Data Extraction.-Information on country of origin, sample size, duration, study design, aspirin dosage, participant characteristics, and outcomes was abstracted independently by 2 authors who used a standardized protocol, Data Synthesis.-Data from 16 trials with 55 462 participants and 108 hemorrhagic stroke cases were analyzed. The mean dosage of aspirin was 273 mg/d and mean duration of treatment was 37 months. Aspirin use was associated with an absolute risk reduction in myocardial infarction of 137 events per 10 000 persons (95% confidence interval [CI], 107-167; P<.001) and in ischemic stroke, a reduction of 39 events per 10 000 persons (95% CI, 17-61; P<.001), However, aspirin treatment was also associated with an absolute risk increase in hemorrhagic stroke of 12 events per In 000 persons (95% CI, 5-20; P<.001). This risk did not differ by participant or study design characteristics. Conclusions.-These results indicate that aspirin therapy increases the risk of hemorrhagic stroke; However, the overall benefit of aspirin use on myocardial infarction and ischemic stroke may outweigh its adverse effects on risk of hemorrhagic stroke in mast populations.