Aim/hypothesis. Leisure-time physical activity can reduce the risk of Type 2 diabetes, but the potential effect of different types of physical activity is still uncertain. This study is to examine the relationship of occupational, commuting and leisure-time physical activity with the incidence of Type 2 diabetes.

Methods. We prospectively followed 6898 Finnish men and 7392 women of 35 to 64 years of age without a history of stroke, coronary heart disease, or diabetes at baseline. Hazards ratios of incidence of Type 2 diabetes were estimated by levels of occupational, commuting, and leisure-time physical activity.

Results. During a mean follow-up of 12 years, there were 373 incident cases of Type 2 diabetes. In both men and women combined, the hazards ratios of diabetes associated with light, moderate and active work were 1.00, 0.70 and 0.74 (p=0.020 for trend) after adjustment for confounding factors (age, study year, sex, systolic blood pressure, smoking, education, the two other types of physical activity and BMI). The multivariate-adjusted hazards ratios of diabetes with none, 1 to 29, and more than 30 min of walking or cycling to and from work were 1.00, 0.96, and 0.64 (p=0.048 for trend). The multivariate-adjusted hazards ratios of diabetes for low, moderate, high levels of leisure-time physical activity were 1.00, 0.67, and 0.61 (p=0.001 for trend); after additional adjustment for BMI, the hazards ratio was no longer significant.

Conclusions/interpretation. Moderate and high occupational, commuting or leisure-time physical activity independently and significantly reduces risk of Type 2 diabetes among the middle-aged general population.