Cardiorespiratory fitness and the incidence of type 2 diabetes: Prospective study of Japanese men

OBJECTIVE - To investigate the association between cardiorespiratory fitness and the incidence of type 2 diabetes among Japanese men. RESEARCH DESIGN AND METHODS - This prospective cohort study was conducted in 4,747 nondiabetic Japanese men, aged 20-40 years at baseline, enrolled in 1985 with follow-up to June 1999. Cardiorespiratory fitness was measured using a cycle ergometer test, and VO_2max was estimated. During a 14-year follow-up, 280 men developed type 2 diabetes. RESULTS - The age-adjusted relative risks of developing type 2 diabetes across quartiles of cardiorespiratory fitness (lowest to highest) were 1.0 (referent), 0.56 (95% CI 0.42-0.75), 0.35 (0.25-0.50), and 0.25 (0.17-0.37) (for trend, P < 0.001). After further adjustment for BMI, systolic blood pressure, family history of diabetes, smoking status, and alcohol intake, the association between type 2 diabetes risk and cardiorespiratory fitness was attenuated but remained significant (1.0, 0.78, 0.63, and 0.56, respectively; for trend, P = 0.001). CONCLUSIONS - These results indicate that a low cardiorespiratory fitness level is an important risk factor for incidence of type 2 diabetes among Japanese men.