Slightly increased BMI at young age is a risk factor for future hypertension in Japanese men

BACKGROUND: Hypertension is developed easily in Asian adults with normal body mass index (BMI) (~23 kg/m(2)), compared with other ethnicities with similar BMI. This study tested the hypothesis that slightly increased BMI at young age is a risk factor for future hypertension in Japanese men by historical cohort study. METHODS: The study participants were 636 male alumni of the physical education school. They had available data on their physical examination at college age and follow-up investigation between 2007 and 2011. The participants were categorized into six categories: BMI at college age of <20.0 kg/m(2), 20.0–21.0kg/m(2), 21.0–22.0kg/m(2), 22.0–23.0kg/m(2), 23.0–24.0kg/m(2), and ≥24.0kg/m(2), and the incidence of hypertension was compared. RESULTS: This study covered 27-year follow-up period (interquartile range: IQR: 23–31) which included 17,059 person-years of observation. Subjects were 22 (22–22) years old at graduated college, and 49 (45–53) years old at first follow-up investigation. During the period, 120 men developed hypertension. The prevalence rates of hypertension for lowest to highest BMI categories were 9.4%, 14.6%, 16.1%, 17.5%, 30.3%, and 29.3%, respectively (p<0.001 for trend), and their hazard ratios were 1.00 (reference), 1.80 (95%CI: 0.65–4.94), 2.17 (0.83–5.64), 2.29 (0.89–5.92), 3.60 (1.37–9.47) and 4.72 (1.78–12.48), respectively (p<0.001 for trend). This trend was similar after adjustment for age, year of graduation, smoking, current exercise status and current dietary intake. CONCLUSION: Slightly increased BMI at young age is a risk factor for future hypertension in Japanese men.