Overweight, obesity and risk of all-cause and cardiovascular mortality in patients with type 2 diabetes mellitus: a dose–response meta-analysis of prospective cohort studies

Overweight and obese individuals with type 2 diabetes are recommended to lose weight, but the associations between excess body weight and all-cause and cardiovascular mortality in patients with type 2 diabetes remain controversial. Therefore, we performed a dose–response meta-analysis to investigate this association. We searched PubMed and Embase through 19th October 2014 and examined the references of retrieved articles to identify relevant prospective cohort studies. A random-effect model was used to calculate the summary risk estimates. Nine studies including 13 cohorts with 161,984 participants were identified. The relative risks (RRs) of all-cause mortality in overweight and obese patients with type 2 diabetes were 0.81 (95 % confidence interval (CI) 0.74–0.90) and 0.72 (95 % CI 0.63–0.81) respectively, compared with the normal or non-overweight patients. Furthermore, a 5 kg/m² increase in body mass index was associated with a significantly reduced risk of all-cause mortality by 5 % (RR 0.95, 95 % CI 0.93–0.97). However, no significant association was found between obese and/or overweight and the risk of cardiovascular mortality in type 2 diabetic patients (RR 0.89; 95 % CI 0.66–1.20 for overweight and RR 0.77; 95 % CI 0.54–1.10 for obesity, respectively). The findings from the present meta-analysis indicate that excess body weight may be a protective factor for all-cause mortality among patients with type 2 diabetes.