Cigarette smoking and risk of stroke and its subtypes among middle-aged Japanese men and women - The JPHC Study Cohort I

Background and Purpose-We examined sex-specific relationships of smoking with risk of total stroke and stroke subtypes in Asian populations because of the limited data available. Methods-A total of 19 782 men and 21 500 women aged 40 to 59 years who were free of prior diagnosis of stroke, coronary heart disease, or cancer and reported their smoking status were followed in the Japan Public Health Center-based Prospective Study on Cancer and Cardiovascular Disease (JPHC Study) from 1990 to 1992 to the end of 2001. Results-During a 461 761 person-year follow-up, 702 total strokes were documented among men, of which 619 were confirmed by imaging studies, including 219 intraparenchymal hemorrhages, 73 subarachnoid hemorrhages, and 327 ischemic strokes. The respective numbers of cases among women were 447, 411, 129, 106, and 176. Multivariate relative risks (95% CIs) for current smokers compared with never-smokers after adjustment for cardiovascular risk factors and public health center were 1.27 (1.05 to 1.54) for total stroke, 0.72 (0.49 to 1.07) for intraparenchymal hemorrhage, 3.60 (1.62 to 8.01) for subarachnoid hemorrhage, and 1.66 (1.25 to 2.20) for ischemic stroke. The respective multivariate relative risks among women were 1.98 (1.42 to 2.77), 1.53 (0.86 to 4.25), 2.70 (1.45 to 5.02), and 1.57 (0.86 to 2.87). There was a dose-response relation between the number of cigarettes smoked and risks of ischemic stroke for men. A similar positive association was observed between smoking and risks of lacunar infarction and large-artery occlusive infarction, but not embolic infarction. Conclusions-Smoking raises risks of total stroke and subarachnoid hemorrhage for both men and women and risk of ischemic stroke, either lacunar or large-artery occlusive infarction, for men.