A Comparison of Two Doses of Aspirin (30 mg vs. 283 mg a Day) in Patients after a Transient Ischemic Attack or Minor Ischemic Stroke

BACKGROUND: Aspirin is known to improve the outcome of patients who have had a cerebral transient ischemic attack, but the optimal dose of aspirin remains uncertain. Experimental evidence indicates that 30 mg of aspirin daily alters platelet aggregation more favorably than the 300-mg dose currently used in patients after transient ischemic attack or minor ischemic stroke. METHODS: We assessed the effects of two doses of a water-soluble preparation of acetylsalicylic acid, or aspirin (30 mg vs. 283 mg a day), on the occurrence of death from all vascular causes, nonfatal stroke, or nonfatal myocardial infarction in a double-blind, randomized, controlled clinical trial in patients who had had a transient ischemic attack or minor stroke. A total of 3131 patients participated in the study. The mean follow-up was 2.6 years. RESULTS: In the group assigned to receive 30 mg of aspirin, the frequency of death from vascular causes, nonfatal stroke, or nonfatal myocardial infarction was 228 of 1555 (14.7 percent), as compared with 240 of 1576 (15.2 percent) in the group assigned to receive 283 mg. The age- and sex-adjusted hazard ratio for the group receiving the lower dose was 0.91 (95 percent confidence interval, 0.76 to 1.09). There were slightly fewer major bleeding complications in the 30-mg group than in the 283-mg group (40 vs. 53), and significantly fewer reports of minor bleeding (49 vs. 84). Fewer patients receiving 30 mg of aspirin reported gastrointestinal symptoms (164 vs. 179) and other adverse effects (73 vs. 90). CONCLUSIONS: Our data indicate that 30 mg of aspirin daily is no less effective in the prevention of vascular events than a 283-mg dose in patients with a transient ischemic attack or minor stroke, and has fewer adverse effects.