Body mass index and the risk of mortality among Chinese adults with Type 2 diabetes.

Aims: To examine the associations between BMI and the risks of all-cause, cardiovascular disease (CVD)-specific and cancer-specific mortality among people with Type 2 diabetes, and thus provide recommendations for weight management in the population.

Methods: This retrospective cohort study was conducted among 52 763 people with newly diagnosed Type 2 diabetes between 1 January 2004 and 31 December 2014 in Shanghai, China. All cases of death were identified by linking to the Shanghai Vital Statistics. Some 52 488 people were included in the analysis. Survival curves for people with different BMI categories were plotted using the Kaplan-Meier method. Cox proportional hazard models within or without restricted cubic spline functions were applied to examine the potential non-linear or linear relationship between BMI and the risk of mortalities respectively.

Results: A total of 4777 deaths were identified during an average of 6-year follow-up. An L-shaped association was observed between BMI and all-cause mortality in men (P for overall association < 0.001 and P for non-linearity < 0.001) while a U-shaped association was found in women (P for overall association < 0.001 and P for non-linearity< 0.001). In men, no significant association was observed for BMI with cancer-specific and CVD-specific mortality. In women, an increased risk of cancer-specific mortality was observed with increasing BMI, whereas decreasing BMI was associated with the increased CVD-specific mortality rate.

Conclusion: The increased all-cause mortality in men with low BMI and in women with either low or high BMI indicate the importance of keeping BMI in a normal range for Chinese adults with Type 2 diabetes.