Leisure-time, occupational, and commuting physical activity and risk of type 2 diabetes in Japanese workers: a cohort study

BACKGROUND: Physical activity has been suggested to reduce the risk of type 2 diabetes. However, evidence is limited regarding whether vigorous-intensity activity yields the same benefits in preventing type 2 diabetes compared with an equivalent dose of moderate-intensity activity as well as other type of physical activity. We examined the risk of type 2 diabetes associated with exercise intensity during leisure and occupational and commuting physical activity among Japanese individuals. METHODS: Participants included 26,628 workers (23,207 men and 3,421 women) aged 30 to 64 years without diabetes at baseline. There was 6 years of follow-up maximum. Leisure-time exercise, occupational physical activity, and duration of walking to and from work were self-reported. Diabetes was diagnosed by using HbA(1c), fasting or random blood glucose, and self-report. We used Cox regression analysis to estimate the hazard ratio (HR) and the 95 % confidence interval (CI) of incident diabetes. RESULTS: During a mean follow-up of 5.2 years, 1,770 participants developed type 2 diabetes. Compared with individuals who engaged in no exercise, the HRs (95 % CIs) for <7.5, 7.5 to <15.0, and ≥15.0 MET-hours per week of exercise were 0.94 (0.81, 1.08), 1.07 (0.88, 1.30), and 0.90 (0.67, 1.21), respectively, among individuals who engaged in moderate-intensity exercise alone; 0.68 (0.44, 1.06), 0.86 (0.54, 1.34), and 0.89 (0.56, 1.41), respectively, among individuals who engaged in vigorous-intensity exercise alone; and 0.70 (0.44, 1.11), 0.57 (0.37, 0.90), and 0.76 (0.52, 1.11), respectively, among individuals who engaged in the two intensities, with adjustments for potential confounders and the total volume of exercise. Occupational physical activity and walking to and from work were not associated with diabetes. CONCLUSIONS: The results suggest that vigorous-intensity exercise can reduce the risk of type 2 diabetes among Japanese workers. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s12889-015-2362-5) contains supplementary material, which is available to authorized users.