Abstract 3786: Exercise Capacity is Associated with Lower Mortality Risk in African-Americans than Caucasians with Type 2 Diabetes
Introduction: Exercise capacity is inversely associated with mortality in healthy and diabetic individuals. African-Americans have a higher prevalence of type 2 diabetes and overall mortality compared to Caucasians. Moreover, there is evidence that African-American diabetics have lower exercise capacity than Caucasians. Consequently, increased exercise capacity may affect African-Americans differently. To test this hypothesis, we assessed relationships between exercise capacity and mortality in African-American and Caucasian diabetics.
Method: African-American (n=1,449; age=60 ± 10) and Caucasian (n=760; age=61 ± 10) male diabetics underwent a routine exercise test. Peak workload was estimated as metabolic equivalents (METs). We categorized those who achieved ≤ 5 METs as Low-Fit, 5.1– 8 METs as Moderate-Fit and >8 METs as High-Fit. The follow-up period was 6.5 ± 4.7 years.
Results: There were 396 (27%) deaths in African-Americans and 141 (18.5%) in Caucasians. After controlling for age, BMI, traditional risk factors and medications, the risk for mortality was higher in African-Americans than Caucasians (RR=1.27; CI: 1.0 –1.5; p=0.018). Exercise capacity was the strongest predictor of risk for mortality for both races. For every 1-MET increase in exercise capacity we observed 15% lower mortality for the entire cohort (RR=0.85; CI: 0.81– 0.90; p<0.001), 16% lower in African-Americans (RR=0.84; CI: 0.78 – 0.89; p<0.001) and 13% lower in Caucasians (RR=0.87; CI: 0.79 – 0.97; p=0.013). When compared to the Low-Fit individuals, the mortality risk for African-Americans was 46% lower for those in the Moderate-Fit (RR=0.54; CI: 0.43– 0.67; P<0.001) and 50% lower for those in the High-Fit category (RR=0.50; CI: 0.33– 0.75; p<0.001). For Caucasians, the mortality risk was lower only for those in the High-Fit category compared to Low-Fit (RR=0.45; CI: 0.23– 0.9; p=0.024) and similar for those in the Low-fit and Moderate-Fit categories (RR=0.74; CI: 0.51–1.0; p=0.10).
Conclusion: Exercise capacity was the strongest predictor of mortality in both African-American and Caucasian men with type 2 diabetes. The exercise capacity necessary for a similar reduction in mortality risk was notably lower for African-Americans than Caucasians.