Threshold of BMI for the Development of Hypertension among Japanese Adults

The optimal value of BMI for the development of hypertension and the influence of BMI on the development of stage 1 or stage 2 hypertension remain unclear.

We sought to identify the BMI threshold for the prevention of hypertension and how changes in BMI would influence the risk of developing hypertension.

We analyzed 1,262,356 participants (median age: 43 y; 50.9% men) with normal blood pressure [BP; systolic BP (SBP) <120 mmHg and diastolic BP (DBP) <80 mmHg] or elevated BP (SBP: 120-129 mmHg and DBP <80 mmHg). The primary outcome was stage 1 (SBP 130-139 mmHg or DBP 80-89 mmHg) or stage 2 hypertension (SBP ≥140 mmHg or DBP ≥90 mmHg). We analyzed the relation between baseline BMI, change in BMI, and the risk of developing hypertension using generalized additive models with a smoothing spline.

During the median follow-up of 851 d, 341,212 cases of stage 1 hypertension and 70,968 cases of stage 2 hypertension were detected. The risk of developing stage 1 or stage 2 hypertension increased steeply after BMI (kg/m²) exceeded 20. The annual change in BMI was positively correlated with the risk of developing stage 1 or 2 hypertension. Contour mapping using generalized additive models demonstrated an additive increase in the risk of developing hypertension with higher baseline BMI and increases in BMI over 1 y. Body-weight gain increases the risk of developing hypertension even in underweight or normal-weight individuals based on the WHO classification.

In Japanese adults with normal or elevated BP, the risk of developing hypertension increased with BMI when baseline BMI was >20. Body-weight gain additively interacted with baseline BMI during hypertension development. Our results underscore the importance of maintaining body weight in preventing the development of hypertension.