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Aspirin therapy reduces stroke by about 25% for persons with atherosclerotic vascular disease, but the effect in those without clinically apparent vascular disease is distinctly different. The lack of reduction of stroke by aspirin for p rimary prevention was incompatible with its protective effect against stroke in patients with manifest vascular disease (P = .001). Intracranial hemorrhage was increased by the regular use of aspirin (relative risk = 1.35; P = .03), similarly for both pr imary and secondary prevention. In 4 large observational studies, self-selected use of aspirin was consistently associated with higher rates of stroke. The effect of aspirin therapy on stroke differs between individuals based on the presence or absence of overt vascular disease, in contrast with the consistent reduction in myocardial infarction by aspirin therapy observed in all populations. We hypothesize that the effect of aspirin therapy on stroke for persons with major risk factors for vascular di sease may be intermediate between a substantial decrease for those with manifest vascular disease and a possible small increase for healthy persons due to accentuated intracranial hemorrhage. When aspirin is given for primary prevention of vascular event s, available data support using 75 to 81 mg/d. |
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