Secondary prevention of ischemic stroke with low dose acetylsalicylic acid.

In order to evaluate the efficacy of low dose acetylsalicylic acid (ASA) for the secondary prevention of ischemic stroke, this cooperative multicenter clinical trial was conducted on a non-blind basis. Patients having a first transient ischemic attack (TIA), reversible ischemic neurological deficit (RIND) or completed ischemic stroke were eligible for this trial. A total of 590 patients including 47 cases of TIA, 23 cases of RIND and 520 cases of completed stroke entered this study. These patients were allocated by the time of admission to one of the following 5 trial regimens: (1) vasodilators having no known inhibitory effect on platelet function (control group), (2) dipyridamole (DP) 50 mg 3 times a day (DP group), (3) ASA 300 mg once a day (ASA 300 mg group), (4) ASA 300 mg once in combination with DP 50 mg 3 times a day (ASADP group), and (5) ASA 100 mg once a day (ASA1 group). No difference in effect between the control and DP groups was observed, nor between the ASA 300 mg and ASADP groups. Therefore, we combined the control and DP groups to make a non-ASA group, and joined the ASA 300 mg and ASADP groups to make an ASA3 group. The differences in the cumulative event-free rate appeared to be significant between the non-ASA group and the ASA3 group and also between the non-ASA group and the ASA1 group. But the frequency distribution of age, territory of stroke, diabetes mellitus, cardiac disease, hematological disease and hyperuricemia were significantly different among these 3 study groups. We thus included these covariates in the Cox's proportional hazard model to control their possible confounding effects.(ABSTRACT TRUNCATED AT 250 WORDS)