[Association between body mass index and both total and cause-specific mortality in China: findings from data through the China Kadoorie Biobank].

Objective: To evaluate the associations between body mass index (BMI) and both total and cause-specific mortality. Methods: After excluding participants with heart disease, stroke, cancer, chronic obstructive pulmonary disease, and diabetes at baseline study, 428 593 participants aged 30-79 in the China Kadoorie Biobank study were chosen for this study. Participants were categorized into 9 groups according to their BMI status. Cox regression analysis was used to estimate the hazard ratios ( HR s) and 95% confidence intervals ( CI s) of mortality on BMI. Results: Among 3 085 054 person-years of the follow-up program between 2004 and 2013 (median 7.2 years), a total of 7 862 men and 6 315 women died. After adjusting for known or potential confounders, an increased risks of all-cause deaths were shown among participants with a BMI less than 18.5 ( HR =1.40, 95 %CI : 1.31-1.50), between 18.5-20.4 ( HR =1.11, 95 %CI : 1.05-1.17), and more than 35.0 ( HR =2.05, 95 %CI : 1.60-2.61), when compared to those with BMI between 20.5-22.4. Ranges of BMI with lower risk of cause-specific mortality were: 18.5-23.9 for ischemic heart disease, <26.0 for cerebro-vascular disease, 26.0-34.9 for cancers, and 24.0-25.9 for respiratory diseases. Conclusions: In this large prospective study, both underweight and obesity were associated with the increased total and certain cause-specific mortality, which were independent from other risk factors of death. Programs related to extensive follow-up, thorough analysis BMI and the risks of incidence on major chronic diseases all need to be developed, in order to better understand the impact of BMI on human health.