The Effect of Age and NT-proBNP on the Association of Central Obesity with 6-Years Cardiovascular Mortality of Middle-Aged and Elderly Diabetic People: The Population-Based Casale Monferrato Study

Background: Among people with type 2 diabetes the relationship between central obesity and cardiovascular mortality has not been definitely assessed. Moreover, NT-proBNP is negatively associated with central obesity, but no study has examined their combined effect on survival. We have examined these issues in a well-characterized population-based cohort. Methods and Findings: Survival data of 2272 diabetic people recruited in 2000 who had no other chronic disease have been updated to 31 December 2006. NT-proBNP was measured in a subgroup of 1690 patients. Cox proportional hazards modeling was employed to estimate the independent associations between cardiovascular and all-cause mortality and waist circumference. Mean age was 67.9 years, 49.3% were men. Both age and NT-proBNP were negatively correlated with waist circumference (r = -0.11, p < 0.001 and r = -0.07, p = 0.002). Out of 2272 subjects, 520 deaths (221 for CV mortality) occurred during a median follow-up of 5.4 years. Central obesity was not associated with CV mortality (hazard ratio, HR, adjusted for age, sex, diabetes duration, 1.14, 95% CI 0.86-1.52). NTproBNP was a negative confounder and age a strong modifier of this relationship (p for interaction <0.001): age <70 years, fully adjusted model HR = 3.52 (1.17-10.57) and age >= 70 years, HR = 0.80 (0.46-1.40). Respective HRs for all-cause mortality were 1.86 (1.03-3.32) and 0.73 (0.51-1.04). Conclusions: In diabetic people aged 70 years and lower, central obesity was independently associated with increased cardiovascular mortality, independently of the negative effect of NT-proBNP. In contrast, no effect on 6-years survival was evident in diabetic people who have yet survived up to 70 years.