Objective: To describe the association of BMI with mortality in patients diagnosed with type 2 diabetes.
Research design and methods: Using records of 106,640 patients in Scotland, we investigated the association between BMI recorded around the diagnosis of type 2 diabetes mellitus (T2DM) and mortality using Cox proportional hazards regression adjusted for age and smoking status, with BMI 25 to <30 kg/m(2) as a referent group. Deaths within 2 years of BMI determination were excluded. Mean follow-up to death or the end of 2007 was 4.7 years.
Results: A total of 9,631 deaths occurred between 2001 and 2007. Compared with the reference group, mortality risk was higher in patients with BMI 20 to <25 kg/m(2) (hazard ratio 1.22 [95% CI 1.13-1.32] in men, 1.32 [1.22-1.44] in women) and patients with BMI ≥35 kg/m(2) (for example, 1.70 [1.24-2.34] in men and 1.81 [1.46-2.24] in women for BMI 45 to <50 kg/m(2)). Vascular mortality was higher for each 5-kg/m(2) increase in BMI >30 kg/m(2) by 24% (15-35%) in men and 23% (14-32%) in women, but was lower below this threshold. The results were similar after further adjustment for HbA1c, year of diagnosis, lipids, blood pressure, and socioeconomic status.
Conclusions: Patients categorized as normal weight or obese with T2DM within a year of diagnosis of T2DM exhibit variably higher mortality outcomes compared with the overweight group, confirming a U-shaped association of BMI with mortality. Whether weight loss interventions reduce mortality in all T2DM patients requires study.