摘要篇首： To the Editor: We read the article by Ke et al1 with great interest, in which they investigated the usage of aspirin for the secondary prevention of ischemic stroke. The incidence of ischemic stroke and transient ischemic attack assessed by onset of clinical symptoms exhibits a marked circadian variation with a peak period during the morning. Stroke usually occurs unexpectedly or more frequently in the morning hours, between 7-12 a.m. In this morning period there is a higher aggregability of thrombocytes. Patients usually take aspirin in the morning for prevention as the treatment regimen is one tablet per day to be swallowed without chewing at least 30 minutes before breakfast (Figure). The highest plasma level of the drug occurs after the morning peak-incidence of the thromboembolic event, suggesting lower prophylactic effect of aspirin. Taking aspirin in the morning has its highest protective effect during the day, when normal physical activity exerts a protective action. Furthermore, this method of daily aspirin administration has its lowest protective value against cardio- and cerebrovascular events during the night and early rooming, when the lack of physical activity further augment the cascade of haemorheological events favoring platelet aggregation and subsequent ischemia.2-5