title: Aspirin and risk of hemorrhagic stroke: a meta-analysis of randomized controlled trials.
abstract: BACKGROUND
  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.
  
  
  METHODS
  Studies were retrieved using MEDLINE (search terms, aspirin, cerebrovascular disorders, and stroke), bibliographies of the articles retrieved, and the authors' reference files.
  
  
  METHODS
  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.
  
  
  METHODS
  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.
  
  
  RESULTS
  Data from 16 trials with 55462 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 10000 persons (95% confidence interval [CI], 107-167; P<.001) and in ischemic stroke, a reduction of 39 events per 10000 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 10000 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 most populations.
authors.affiliation: Department of Biostatistics and Epidemiology, Tulane University School of Public Health and Tropical Medicine, New Orleans, LA 70112, USA. jhe@mailhost.tcs.tulane.edu
authors.forename: J
authors.initials: J
authors.lastname: He
authors.forename: P K
authors.initials: PK
authors.lastname: Whelton
authors.forename: B
authors.initials: B
authors.lastname: Vu
authors.forename: M J
authors.initials: MJ
authors.lastname: Klag
mesh_terms: D001241:Aspirin / Q000009:adverse effects* / Q000627:therapeutic use; D002545:Brain Ischemia / Q000517:prevention & control; D002543:Cerebral Hemorrhage / Q000209:etiology*; D006801:Humans; D009203:Myocardial Infarction / Q000517:prevention & control; D010975:Platelet Aggregation Inhibitors / Q000009:adverse effects* / Q000627:therapeutic use; D016032:Randomized Controlled Trials as Topic; D012044:Regression Analysis; D012306:Risk
chemical_list: D010975:Platelet Aggregation Inhibitors; D001241:Aspirin