Prevalence and Determinants of Prehypertension in a Japanese General Population: The Jichi Medical School Cohort Study

It has been reported that subjects with prehypertension (pre-HT) (systolic blood pressure [SBP] 120-139 mmHg and/or diastolic blood pressure [DBP] 80-89 mmHg) have an increased risk of cardiovascular disease (CVD). We evaluated the prevalence and determinants of pre-HT in a Japanese general population. We enrolled 4,706 males and 7,342 females aged 18 to 90 years whose BPs were measured at baseline. The subjects' BPs were classified as follows: normotension (NT: SPB/DBP<120/80 mmHg), pre-HT (120/80-139/89 mmHg), and hypertension (HT: >= 140/90 mmHg or treated hypertension). The prevalence of pre-HT was 34.8% (males), and 31.8% (females). Body mass index (BMI) of more than 23.0 kg/m(2) was the strongest determinant of pre-HT (Males-BMI: 23.0-24.9 kg/m(2), odds ratio [OR]=1.47, 95% confidence interval [Cl]=1.21-1.79; BMI: 25.0-26.9 kg/m(2), OR=2.20,95% CI=1.68-2.87; BMI: 27.0-29.9 kg/m(2), OR=2.75, 95% CI=1.80-4.19; BMI: >= 30.0 kg/m(2), OR=3.39, 95% CI=1.21-9.46. Females-BMI: 23.0-24.9 kg/m(2), OR=1.67, 95% CI=1.421.95; BMI: 25.0-26.9 kg/m(2), OR=1.79,95% CI=1.46-2.19; BMI: 27.0-29.9 kg/m(2), OR=3.65, 95% CI=2.73-4.89; BMI: >= 30.0 kg/m(2), OR=4.23, 95% CI=2.33-7.70). The other determinants of pre-HT were hyperlipidemia (Males: OR=1.25; Females: OR=1.43), and aging (by 10 years; Males: OR=1.12; Females: OR=1.48). Determinants of pre-HT in females were impaired glucose tolerance (OR=1.41, 95% CI=1.03-1.94), diabetes (OR=2.01, 95% CI=1.16-3.47) and a family history of HT in both parents (OR=1.90, 95% CI=1.38-2.62), whereas in males the only other predictor was alcohol drinking (OR = 1.45, 95% CI = 1.23-1.70). In conclusion, even subjects with a mild increase of BMI (23.0-24.9 kg/m2) had an increased risk of pre-HT in a Japanese population, and the level of BMI associated with pre-HT was lower than that in Western countries. Additionally, there were gender differences in the determinants of pre-HT. (Hypertens Res 2008; 31: 1323-1330)