Long-term Impact of Cardiorespiratory Fitness on Type 2 Diabetes Incidence: A Cohort Study of Japanese Men

Background: We sought to examine the association between cardiorespiratory fitness (CRF) and incidence of type 2 diabetes considering the follow-up period in a cohort of Japanese men with a maximum follow-up period of 23 years. Methods: This study enrolled 7,804 male workers free of diabetes in 1986. CRF was measured using a cycle ergometer, and maximal oxygen uptake was estimated. During 1986-2009, participants were followed for development of type 2 diabetes, which was diagnosed using fasting blood tests, self-administered questionnaires, or oral glucose tolerance tests after urinary tests from annual health checkups. Hazard ratios for the incidence of type 2 diabetes were estimated using Cox proportional hazards models. Results: During the follow-up period, 1,047 men developed type 2 diabetes. In analyses by follow-up periods (1986-1993, 1994-2001, and 2002-2009), there was an inverse dose-response relationship between CRF and the development of type 2 diabetes for all three follow-up periods (P for trend 0.019, <0.001, and 0.001, respectively), and the association between CRF at baseline and the incidence of type 2 diabetes did not weaken with longer follow-up period. Compared with the lowest CRF group, hazard ratios of developing type 2 diabetes were 0.69 (95% confidence interval [CI], 0.49-0.97) for the highest CRF group in 1986-1993, 0.57 (95% CI, 0.42-0.79) for the highest CRF in 1994-2001, and 0.47 (95% CI, 0.30-0.74) for the highest CRF in 2002-2009. Conclusion: High CRF is associated with a lower risk of the incidence of type 2 diabetes over an extended period of >20 years among men.