Risk of stroke in male cigarette smokers.

From 1965 to 1968, the Honolulu Heart Program began following 8006 men of Japanese ancestry in a prospective study of cardiovascular disease. Of the subjects who had not had a stroke by the time of study entry, 3435 were cigarette smokers and 4437 were nonsmokers. In 12 years of follow-up, 171 smokers and 117 nonsmokers had a stroke. As compared with nonsmokers, cigarette smokers had two to three times the risk of thromboembolic or hemorrhagic stroke, after control for age, diastolic blood pressure, coronary heart disease, and other risk factors (P less than 0.001). Subjects who continued to smoke in the course of follow-up had the highest risk of stroke. When these subjects were compared with those who never smoked, their risk of hemorrhagic events was increased four- to six-fold (P less than 0.001). Subjects who were smokers at study entry but stopped smoking in the course of follow-up had a slight excess risk of stroke. When these subjects were compared with those who continued to smoke, however, their risk was reduced by more than half after adjustment for risk factors (P less than 0.05), indicating that stopping smoking had significant benefits.