Body mass index and mortality among middle-aged Japanese individuals with diagnosed diabetes: The Japan Public Health Center -based prospective study (JPHC study)

Aim: To examine the association between body mass index (BMI) and mortality among middle-aged people with diabetes in Japan. Methods: A total of 3032 men and 1615 women, aged 40–69 years, with diabetes were analyzed. Cox proportional hazards models, adjusted for potential confounding factors, were used to estimate mortality hazard ratios (HRs) across BMI categories at the baseline. Results: There were 1761 deaths during a mean follow-up period of 18.5 years. Increased all-cause mortality was observed at both ends of the BMI distribution; compared with the reference BMI category (23.0–24.9 kg/m2), the HRs were 1.25 (95% confidence interval [CI], 0.9997–1.56) in the lowest (14.0–18.9 kg/m2) and 1.36 (95% CI, 1.06–1.74) in the highest (30.0–39.9 kg/m2) categories (P = 0.001). Similar all-cause mortality trends were observed after excluding deaths within 3 years of follow-up, as well as for men and men who had ever smoked. While a similar non-linear pattern was observed for cancer-specific mortality, heart disease-specific mortality was only increased in the highest BMI category (HR, 1.86; 95% CI, 1.06–3.25). Conclusion: This population-based prospective study demonstrated increased all-cause mortality at both ends of the BMI distribution among Japanese people with diabetes. © 2020 Elsevier B.V.