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.