Aspirin and Risk of Hemorrhagic Stroke

To the Editor: Dr He and colleagues¹ claim that the overall benefit of aspirin use on myocardial infarction and ischemic stroke outweighs its risk of hemorrhagic stroke in most populations. However, they also suggest that the risk-benefit ratio of aspirin treatment for prevention of cardiovascular disease in populations with a high risk of hemorrhagic stroke should be addressed in subsequent studies.

Indeed, Asian people have been known to have such an increased risk of brain hemorrhage in comparison to brain infarction and myocardial infarction.² For example, crude annual incidence rate of stroke and myocardial infarction per 10,000 population aged 40 years or older during 1988-1991 in Japanese people in Okinawa were as follows³: 8 events for myocardial infarction, 18 for ischemic stroke, and 14 for hemorrhagic stroke. By applying the relative risks calculated by He and colleagues (relative risk reduction of 32% for myocardial infarction and 18% for ischemic stroke, respectively, and relative risk increase of 84% for hemorrhagic stroke) for Japanese people in Okinawa, aspirin use would be associated with an absolute risk reduction in myocardial infarction of 3 events per 10,000 persons and, for ischemic stroke, a reduction of 3 events per 10,000 persons. However, aspirin treatment also would be associated with an absolute risk increase in hemorrhagic stroke of 12 events per 10,000 persons. Likewise, the number needed to treat to prevent 1 event would be 3333 for myocardial infarction and 3333 for ischemic stroke. The number needed to treat to cause 1 event would be 833 for hemorrhagic stroke.