Underweight rather than adiposity is an important predictor of death in rural Chinese adults: a cohort study

Background To assess the associations of body mass index (BMI) with all-cause and cause-specific mortalities among rural Chinese. Methods A prospective study of 28 895 individuals was conducted from 2006 to 2014 in rural Deqing, China. Height and weight were measured. The association of BMI with mortality was assessed by using Cox proportional hazards model and restricted cubic spline regression. Results There were a total of 2062 deaths during an average follow-up of 7 years. As compared with those with BMI of 22.0-24.9 kg/m(2), an increased risk of all-cause mortality was found for both underweight men (BMI <18.5 kg/m(2)) (adjusted HR (aHR): 1.45, 95% CI: 1.18 to 1.79) and low normal weight men (BMI of 18.5-21.9 kg/m(2)) (aHR: 1.20, 95% CI: 1.03 to 1.38). A J-shaped association was observed between BMI and all-cause mortality in men. Underweight also had an increased risk of cardiovascular disease and cancer mortalities in men. The association of underweight with all-cause mortality was more pronounced in ever smokers and older men (60+ years). The results remained after excluding participants who were followed up less than 1 year. Conclusion The present study suggests that underweight is an important predictor of mortality, especially for elderly men in the rural community of China.