Sex differences in the relationship between obesity and hypertension in Japan: a large population-based cross-sectional study.

We examined the effect of sex on the relationship between obesity and hypertension among Japanese people, who generally have a lower prevalence of obesity than Westerners. We analyzed the results of specific health checkups for Japanese aged 40-74 years (688,306 men and 891,191 women) obtained in 2011. The participants were divided into four age groups (40-49, 50-59, 60-69, and 70-74 years) and five body mass index (BMI) categories (≤ 24.9 [non-overweight/obesity], 25.0-26.9 and 27.0-29.9 [overweight], 30.0-34.9 and ≥ 35.0 kg/m [obesity]). The odds ratio for hypertension in each BMI category was calculated using normal weight as the reference. The prevalence of hypertension was 26.8%-65.5% for men and 17.6%-53.6% for women in the overweight or obesity categories in the 40-49 age group, and 72.0%-88.7% for men and 70.1%-90.6% for women in the 70-74 age group. In women aged 40-49, the prevalence of hypertension in each BMI category was approximately 10% lower than that in men, but there was almost no difference between men and women in the 70-74 age group. On the other hand, the odds ratio for hypertension was higher in women than in men across all BMI categories and age groups. A stronger relationship between obesity and hypertension was observed in women than in men in all age groups. Japanese women have not been the target of studies for obesity, but more attention should be paid to Japanese women with obesity.