Aspirin, Platelet Aggregation, and the Circadian Variation of Acute Thrombotic Events

The onset of several acute cardiovascular diseases occurs in a circadian pattern, with a peak incidence in the hours soon after awakening. This finding, coupled with laboratory data that confirm a surge in platelet activation during the early morning hours, suggests that acute changes in platelet aggregability may be an important trigger of thrombosis. Therefore, the efficacy of antiplatelet agents, such as aspirin, in reducing risks of vascular occlusion may result, at least in part, from a blunting of these short-term changes in platelet aggregability. In this review, clinical and laboratory evidence describing these cyclical changes is discussed, as is current evidence of the effects of aspirin on platelet function and the circadian variation of acute thrombosis.