Background: Few studies have allowed direct comparison of the association between body mass index (BMI; in kg/m2) and hypertension in different Asian ethnicities.

Objective: We compared the association of BMI with hypertension in Chinese, Indonesian, and Vietnamese adults and determined BMI cutoffs that best predicted hypertension in these populations.

Design: We included 7562 Chinese, 18,502 Indonesian, and 77,758 Vietnamese participants aged 18–65 y. Blood pressure, weight, and height were measured by trained health workers. To define an optimal BMI cutoff, we computed and searched for the shortest distance on receiver operating characteristic curves.

Results: Despite a low mean BMI, the prevalences of hypertension in Chinese, Indonesian, and Vietnamese men were 22.9%, 24.8%, and 14.4%, respectively, and in women were 16.6%, 26.9%, and 11.7%, respectively. At all BMI levels, the sex-specific prevalence of hypertension was higher in Indonesian adults than in Chinese and Vietnamese adults (P < 0.05 at almost all BMI levels). The overall and stratified analyses suggested optimal BMI cutoffs of 23–24, 21–22.5, and 20.5–21 for Chinese, Indonesian, and Vietnamese adults, respectively. The cutoffs were ˜0.5–1.0 units higher in women than in men and in the older (41–65 y) than in the younger (18–40 y) participants.

Conclusions: The study showed an ethnic difference in the BMI-hypertension association and in optimal BMI cutoffs between Chinese, Indonesian, and Vietnamese adults. Country-specific or even country-, sex-, and age-specific BMI cutoffs might be needed to identify persons at high risk of cardiovascular diseases.