Body mass index and mortality among Japanese patients with type 2 diabetes: pooled analysis of the Japan diabetes complications study and the Japanese elderly diabetes intervention trial.

Abstract

Previous studies on the association between body mass index (BMI) and mortality in diabetes do not necessarily provide a comprehensive view in terms of the global population because of the exclusion of individuals with a BMI less than 18.5 kg/m(2). The objective of the study was to examine the association between BMI and mortality. We analyzed pooled data from 2 cohorts of 2620 Japanese patients with type 2 diabetes followed up for 6.3 years. Patients with a history of cardiovascular disease or cancer were excluded. The end point was all-cause mortality. Hazard ratios were estimated by Cox regression adjusted for age, smoking, leisure-time physical activity, and other confounders. An analysis using BMI categories of 14.4-18.5 (5.2%), 18.5-22.4 (37.3%), 22.5-24.9 (31.0%), and 25.0-37.5 kg/m(2) (26.6%) revealed no significant trend in mortality among patients with a BMI of 18.5 kg/m(2) or greater (trend P = .69). In contrast, the hazard ratio of patients with a BMI less than 18.5 kg/m(2) vs 22.5-24.9 kg/m(2) was 2.58 (95% confidence interval 1.38-4.84; P < .01). Exclusion of deaths in the first 4 years of follow-up decreased the hazard ratio only slightly. The lowest mortality rate was observed among patients with a BMI of 18.5-24.9 kg/m(2), and obesity had no benefits regarding mortality. Further research is needed in lean patients, especially among aging populations in East Asia.