Prospective study of aspirin use and risk of stroke in women

Background and Purpose-In secondary prevention, aspirin reduces risk of isc hemic stroke. In primary prevention of stroke, however, the role of aspirin is uncertain, especially in women. Methods-In 1980, 79 319 women in the Nurses' Health Study cohort, 34 to 59 years of age and free of diagnosed cardiovascular disease, cancer, and rheu matoid arthritis, completed questionnaires that included information on asp irin use. Data on aspirin use were updated in 1982, 1984, and 1988. By 1994 , after 994 231 person-years of follow-up, 503 incident strokes (295 ischem ic strokes, 100 subarachnoid hemorrhages, 52 intraparenchymal hemorrhages, and 56 strokes of undetermined type) were documented. Results-There was no clear relationship between aspirin use and risk of tot al stroke; risk was slightly reduced among women who took 1 to 6 aspirin pe r week and slightly increased among women who took 7 or Inert aspirin per w eek. Women who took 1 to 6 aspirin per week had a lower risk of large-arter y occlusive infarction compared with women who reported no aspirin use; aft er simultaneous adjustment for other cardiovascular risk factors and select ed nutrients, the multivariate relative risk was 0.50 (95% CI 0.29 to 0.85, P=0.01). Women who took 15 or more aspirin per week had an excess risk of subarachnoid hemorrhage; the multivariate relative risk was 2.02 (95% CI 1. 04 to 3.91, P for trend=0.02). The reduction in large-artery occlusive infa rction with aspirin was of greater magnitude for older, hypertensive, or sm oking women than for younger, nonhypertensive, or nonsmoking women; the ele vation in subarachnoid hemorrhage with aspirin was also more apparent for o lder or hypertensive women than for younger or nonhypertensive women. Aspir in use was not associated with risk of other subtypes of stroke. Conclusions-These prospective data indicate that women who take 1 to 6 aspi rin per week have a reduced risk of large-artery occlusive infarction, but those who use 15 or mon aspirin per week have an increased risk of subarach noid hemorrhage. This observational study suggests benefits of aspirin for ischemic stroke with low frequency of use and hazards for hemorrhagic strok e with high frequency of use, particularly among older or hypertensive wome n. Thus, the effect on total stroke will depend on the dose of aspirin and the distribution of stroke subtypes and risk factors in the population.