Risk of hospitalized stroke in men enrolled in the Honolulu Heart Program and the Framingham Study: A comparison of incidence and risk factor effects.

BACKGROUND AND PURPOSE Risk of death due to stroke in Japan is more than double the risk in the United States. It remains unknown why some ethnic groups are more prone to stroke than others. Our purpose was to compare the 20-year incidence of hospitalized stroke between Japanese-American men in the Honolulu Heart Program and white men in the Framingham Study. METHODS This was a 20-year follow-up study beginning around 1965, a population-based study on the island of Oahu, Hawaii, and in Framingham, Mass. Participants were 7589 men in Honolulu and 1216 men in Framingham without prevalent coronary heart disease and stroke. Subjects were 45 to 68 years old when follow-up began. Main outcome measures were incident thromboembolic and hemorrhagic stroke. RESULTS Framingham men had a 40% excess of thromboembolic stroke compared with Honolulu men after adjustment for age and other risk factors (62/1000 versus 45/1000, respectively, P<0.001), whereas incidence of hemorrhagic stroke was nearly identical (14.8/1000). In both cohorts, each stroke type was consistently elevated in the presence of hypertension and cigarette smoking. Diabetes and body mass index increased the risk of thromboembolic stroke in both samples, and diabetes increased the risk of hemorrhagic events in Framingham. Alcohol intake and low total cholesterol were associated with hemorrhagic events in Honolulu but not in Framingham. Despite occasional differences in risk factor effects, none were significantly different between cohorts. CONCLUSIONS The incidence of thromboembolic stroke requiring hospitalization is markedly less in Honolulu than in Framingham. The difference in stroke incidence rates observed cannot be explained by the traditional risk factors. Further studies are needed to identify factors that protect Japanese-American men in Honolulu from stroke.