Changes in body mass index before and during economic development and subsequent risk of cardiovascular disease and total mortality: a 35-year follow-up study in China Running title: BMI and mortality in China

OBJECTIVE—It is unclear whether changes in body mass index (BMI) during rapid economic development influence subsequent mortality. RESEARCH DESIGN AND METHODS— We analyze whether BMI in 1976 and 1994, and changes in BMI during 1976-1994 predict cardiovascular disease (CVD) and all-cause mortality in a 35-year follow-up cohort of 1,696 Chinese (1,124 men and 572 women, aged 35-65 years) in Xi'an, China. Participants were categorized as underweight (<18.5 kg/m), normal weight (18.5-24.9 kg/m), and overweight (≥25.0 kg/m). RESULTS—During 51,611 person years of follow-up, we identified 655 deaths from all-causes and 234 from CVD. From 1976-1994, the prevalence of overweight rose from 9.2% to 27.8%. With each unit increment in 1976 BMI, multivariate hazard ratios (HRs) (95%CI) were 0.78 (0.72-0.84) for CVD and 0.91(0.87-0.95) for all-cause mortality. In contrast, corresponding HRs were 1.14 (1.08-1.19) and 1.05 (1.01-1.08) in 1994 BMI. The HRs for each unit increment in BMI change from 1976-1994 were 1.35 (1.25-1.41) for CVD and 1.09 (1.05-1.13) for all-cause. Compared to participants with stable normal weight in 1976 and 1994, HRs of all-cause mortality for those who had normal weight in 1976 but became overweight in 1994 and for those who were persistently overweight during 1976-1994 were 1.42 (1.12-1.80) and 1.80 (1.04-3.14), respectively. CONCLUSIONS—Gaining weight with increased BMI at middle age in Chinese during economic development was associated with elevated risks of all-cause and