BMI and all-cause mortality among Chinese and Caucasians: the People's Republic of China and the Atherosclerosis Risk in Communities Studies.

Background: Lower ethnic-specific body mass index (BMI) cutpoints have been proposed for Asians and adapted in some countries. However, to our knowledge, no study has directly compared Asians to other ethnic groups to test differences in associations between BMI and all-cause mortality using common methods.
Objectives: We estimated the association between BMI and all-cause mortality in Chinese Asians and Caucasian Americans to determine if lower Asian-specific BMI cutpoints are warranted.
Methods: Extant data of the People's Republic of China Study (1983-1997) including 5546 Chinese and the Atherosclerosis Risk in Communities Study (1987-2002) including 9932 Caucasians aged 45-64 years at baseline were used. All analyses were performed using Cox proportional regression models.
Results: Standardized mortality rates were 6.88 (95% confidence interval (CI): 5.75-8.24) and 5.50 (95% CI: 4.74-6.39) per 1000 person-years for Chinese and Caucasians, respectively. Standardized mortality probabilities by age 70 were similar across all BMI categories among Chinese. Furthermore, the probabilities were similar to those among Caucasians with BMI of 27.5-<32.5 kg/m2. The BMI associated with lowest mortality risk was almost identical between Chinese (25.1 kg/m2) and Caucasians (25.2 kg/m2). The analysis of categorical BMI did not reveal an increased mortality risk at any BMI category among Chinese. In contrast, compared to those with a BMI of 23.0-<25.0 kg/m2, risk was elevated by 35% among Caucasians with a BMI of 30.0-<32.5 kg/m2.
Conclusions: These findings do not support different BMI cutpoints for Chinese than Caucasians on the basis of mortality rates.