Body mass index and stroke incidence in a Japanese community: the Hisayama study

Although obesity is one of the major risk factors for coronary heart disease, its role in the development of stroke remains controversial. A total of 2,421 residents, aged 40-79 years of a Japanese community were followed up prospectively for 12 years. The subjects were divided into four groups according to body mass index (BMI) levels (<21.0, 21.0-22.9, 23.0-24.9 and ≥ 25.0 kg m(-2)). During the follow-up, 107 ischemic and 51 hemorrhagic strokes occurred. The age-adjusted incidence of ischemic stroke for men significantly increased with increasing BMI levels (P for trend=0.005). This association remained substantially unchanged even after adjustment for other risk factors: namely, systolic blood pressure, electrocardiogram abnormalities, diabetes, total cholesterol, high-density lipoprotein-cholesterol, triglycerides, smoking habits, alcohol intake and regular exercise (P for trend<0.001). Compared with that of the BMI levels of <21.0 kg m(-2), the multivariate-adjusted risk of ischemic stroke was significant even in the BMI levels of 23.0-24.9 kg m(-2) (multivariate-adjusted hazard ratio (HR)=3.12; 95% confidence interval (CI), 1.24-7.87; P=0.02) as well as in the BMI levels of ≥ 25 kg m(-2) (multivariate-adjusted HR=5.59; 95% CI, 2.09-14.91; P<0.001). In stratified analyses, the risk of ischemic stroke for men synergistically increased in subjects having both obesity and diabetes or a smoking habit. We found no significant associations between BMI levels and ischemic stroke in women and between BMI levels and hemorrhagic stroke in either sex. In conclusion, our findings suggest that overweight and obesity are independent risk factors for ischemic stroke in Japanese men.