Effect of Risk Factors on Exercise Capacity in NIDDM

Exercise capacity has been used as a noninvasive parameter for predicting cardiovascular events. It is known that diabetic patients have an impaired exercise capacity when compared with nondiabetic age-matched control subjects, but the risk factors associated with this impairment have not been thoroughly analyzed. A total of 453 male and female NIDDM patients who underwent graded exercise testing with expired gas analysis were studied to determine the possible influences of demographic and cardiac risk factors on exercise capacity. Univariate and multiple linear regression analyses were performed on baseline patient characteristics with respect to peak oxygen consumption (VO₂). In the regression analyses, African-American race was strongly associated with a decrease in peak VO₂; the difference in means between African-Americans and other subjects for men was −2.50 ml.kg⁻¹ · min⁻¹ (−4.28, −0.07, 95% CI) (P < 0.006) and for women was −2.96 ml.kg⁻¹ · min⁻¹ (−4.45, −1.47) (P < 0.0002). Univariate analyses revealed that African-American subjects had increased prevalence, longer duration, and higher systolic and diastolic hypertension than the non-Hispanic and Hispanic whites. Other independent predictors of peak VO₂ (reported as change in peak VO₂ in milliliters per kilogram per minute) were BMI (men: −0.39 kg/m² [−0.52, −0.29], P < 0.0001; women: −0.39 kg/m² [−0.48, −0.31], P < 0.0001), age (men: −0.16/year [−0.23, −0.09], P < 0.0001; women: −0.17/year [−0.24, −0.11], P < 0.0001), baseline resting systolic blood pressure (men: −0.03/mmHg [−0.06, −0.01], P < 0.05; women: −0.03/mmHg (−0.06, −0.01], P< 0.05), and pack-years smoking (men: −0.04/pack-years [−0.04, −0.01], P < 0.01; women: −0.04/pack-years [−0.07, −0.01], P < 0.0001). Thus, in this large NIDDM study, weight loss, smoking cessation, and aggressive blood pressure control, particularly in African-Americans with NIDDM, would appear to be important in improving exercise capacity and potentially improving the increased cardiovascular mortality associated with an impaired exercise capacity.