Modifying Effect of Body Mass Index on Survival in Elderly Type 2 Diabetic Patients: Hong Kong Diabetes Registry.

Objective: There are nonlinear risk associations of body mass index (BMI) with mortality in type 2 diabetes (T2D) and elderly populations although similar information in elderly individuals with T2D are lacking.

Research Design And Methods: We analyzed prospective data for 3186 Chinese patients with T2D with age 65 years or older. Baseline demographic data, risk factors, complications, and all-cause mortality were captured from the Hong Kong Diabetes Registry and the Hong Kong Hospital Authority Clinical Management System.

Results: Over a median follow-up period of 6.0 years (medium-term), 816 (25.6%) deaths occurred and at 9.4 years (long-term), 1557 (48.9%) patients had died. Men were more likely to die than women with increased mortality rate with increasing age (morality rates of men with normal BMI at 9-year follow-up in the 65 to 69, 70 to 74, and 75 years or older age groups were 41.8, 70.3, and 101.4 per 1000 person-years, whereas that for women were 35.5, 50.4, and 78.8 respectively). Within each age group, high BMI was associated with increased survival, especially in the 75 years and older age group and with prolonged follow-up period. Using Cox regression analysis, after adjustment for confounders, high BMI (≥ 25.0 kg/m(2)) was associated with reduced risk of death in all subgroups, reaching significance in men in the older age groups at 9-year follow-up (for men 70 to 74 years old, hazard ratio [HR] of mortality was 0.67, 95% confidence interval [CI] 0.48-0.95, for those ≥ 75, HR was 0.62, 95% CI 0.44-0.89) compared with 18.5 to 22.9 kg/m(2) as referent.

Conclusions: In Chinese elderly patients with T2D, high BMI protected against mortality, calling for more attention to people with low BMI who might have unmet clinical needs.