Purpose: Clinical guidelines developed in the United States are used frequently in other countries without assessment of their appropriateness in non-U.S. populations. We explored the relevance of recent U.S. guidelines for the use of aspirin for the primary prevention of cardiovascular events in the Japanese population.
Methods: From a systematic search of published data, estimates were derived for rates of coronary heart disease, hemorrhagic stroke, and major gastrointestinal bleeding for the Japanese population and for subgroups with different risk factors. Odds ratios derived from meta-analyses were used to assess the potential benefits and risks of aspirin use.
Results: The estimated incidence of coronary heart disease in middle-aged men in Japan is lower than in the United States (1.57 vs. 6.0 per 1000 person-years), while that of hemorrhagic stroke is higher (1.14 vs. 0.37 per 1000 person-years). Because of higher baseline rates of hemorrhagic diseases, the expected reduction in cardiovascular events with aspirin use would be offset by a greater increase in hemorrhagic complications for women and most men in Japan, except for those with both hypertension and diabetes. To achieve the same 2:1 ratio of coronary heart disease events avoided to hemorrhagic events caused that is implied by the 3% threshold for 5-year coronary disease risk in U.S. guidelines, a 6% to 14% risk threshold, depending on patient age, seems appropriate for recommending aspirin in Japanese patients.
Conclusion: The thresholds of antiplatelet therapy for Asian populations should be two to five times higher than those for the U.S. population because of higher risks of hemorrhagic complications. The assumptions and implications of U.S. guidelines should be evaluated before use in other countries.