Association between BMI measured within a year after diagnosis of type 2 diabetes and mortality

To describe the association of BMI with mortality in patients diagnosed with type 2 diabetes.

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.

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.

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.