Effects of cardiorespiratory fitness on aging: glucose trajectory in a cohort of healthy men.

Purpose: We modeled the age-related trajectory of glucose and determined whether cardiorespiratory fitness altered the trajectory in a cohort of men from the Aerobics Center Longitudinal Study.

Methods: A total of 10,092 men free of diagnosed diabetes, cardiovascular disease, and cancer, ages 20 to 90 years, completed from 2 to 21 health examinations between 1977 and 2005. Cardiorespiratory fitness was measured by a maximal treadmill exercise test and normalized for age. The covariates included waist circumference, hypertension, elevated cholesterol, smoking behavior, and physical activity.

Results: Linear mixed models regression analysis showed that fasting glucose increased at a linear rate with aging. Glucose increased at a yearly rate of 0.17 mg/dL (95% confidence interval: 0.16-0.19). Fitness had little influence on the aging glucose trajectory below age 35, but significantly influenced the trend after age 35 (P for interaction < .001). The aging-related glucose increases in low-fitness men (0.25 mg/dL per year) was greater than average-fitness (0.15 mg/dL per year) and high-fitness (0.13 mg/dL per year) men.

Conclusions: The aging-related fasting glucose increases in low-fitness men was nearly double that of high-fitness men. Our results may suggest that it is possible to delay the age-related glucose impairment through increasing one's fitness level.