Abstract

Objective: Assess the association between exercise capacity and mortality in African-Americans and Caucasians with type 2 diabetes and explore racial differences regarding this relationship.

Research Design and Methods: African-American (n=1,703; age=60±10) and Caucasian (n= 1,445; age=62±10) men with type 2 diabetes completed a maximal exercise test between 1986 and 2007 at the Veterans Affairs Medical Centers in Washington, DC and Palo Alto, California. Three fitness categories were established (Low, Moderate and High-Fit) based on peak metabolic equivalents (METs) achieved. They were followed for all-cause mortality for 7.3±4.7 years.

Results: The adjusted mortality risk was 23% higher in African-Americans compared to Caucasians (hazard ratio=1.23; CI: 1.1-1.4). A graded reduction in mortality risk was noted with increased exercise capacity for both races. There was a significant interaction between race and METs (p<0.001), and among race and fitness categories (p<0.001). The association was stronger for Caucasians. Each 1-MET increase in exercise capacity yielded 19% lower risk for Caucasians and 14% for African-Americans (p<0.001). Similarly, the risk was 43% lower (hazard ratio=0.57; CI: 0.44-0.73) for Moderate-Fit and 67% lower (hazard ratio=0.33; CI: 0.22-0.48) for High-Fit Caucasians. The comparable reductions in African-Americans were 34% (hazard ratio=0.66; CI: 0.55-0.80), and 46% (hazard ratio=0.54; CI: 0.39-0.73) respectively.

Conclusion: Exercise capacity is a strong predictor of all-cause mortality in African-American and Caucasian men with type 2 diabetes. The exercise capacity-related reduction in mortality appears to be stronger and more graded for Caucasians than for African-Americans.