Cardiorespiratory fitness and the incidence of type 2 diabetes: a cohort study of Japanese male athletes

BACKGROUND In Japan, although the incidence of overweight (BMI ≥ 25) is still low compared with that in Europe and the United States, the prevalence of type 2 diabetes has increased over the last 15 years,. In both Japanese and Caucasian populations it has been reported that a high level of cardiorespiratory fitness protects against the development of type 2 diabetes. However, there are no reports focused specifically on athletes that investigate whether high cardiorespiratory fitness at a young age can prevent disease later in life. We examined the relationship between cardiorespiratory fitness at a young age and the development of type 2 diabetes in Japanese athletes using a cohort study. METHODS The cardiorespiratory fitness of male alumni of the physical education department of Juntendo University, as measured by stored data of a 1,500-m endurance run in college (1971-1991) was compared with their incidence of type 2 diabetes as determined by follow-up questionnaires (2007-2009). This study used Cox's proportional hazards models and adjusted for age, year of graduation, BMI, smoking, and sports club participation at college age. RESULTS We collected data on cardiorespiratory fitness at college age and medical history survey data during 2007-2009 from 570 male alumni. The median follow-up period was 26 years (IQR: 23-29 years), and 22 men had developed type 2 diabetes. An inverse relationship was observed between incidence of type 2 diabetes and level of cardiorespiratory fitness at time of college after adjustment for age, year of graduation, BMI, smoking, and sports participation. The adjusted hazards ratio and 95% CI by category (low, medium, and high) were 1.00 (reference), 0.40 (0.14-1.13) and 0.26 (0.07-1.00) (p = 0.03 for trend). CONCLUSIONS A high level of cardiorespiratory fitness at a young age can help prevent type 2 diabetes later in life.