Physical activity and television watching in relation to risk for type 2 diabetes mellitus in men

Background: Television (TV) watching, a major sedentary behavior in the Uni ted States, has been associated with obesity. We hypothesized that prolonge d TV watching may increase risk for type 2 diabetes. Methods: In 1986, 37918 men aged 40 to 75 years and free of diabetes, cardi ovascular disease, and cancer completed a detailed physical activity questi onnaire. Starting from 1988, participants reported their average weekly tim e spent watching TV on biennial questionnaires. Results: A total of 1058 cases of type 2 diabetes were diagnosed during 10 years (347 040 person-years) of follow-up. After adjustment for age, smokin g, alcohol use, and other covariates, the relative risks (RRs) for type 2 d iabetes across increasing quintiles of metabolic equivalent hours (MET-hour s) per week were 1.00, 0.78, 0.65, 0.58, and 0.51 (P for trend, < .001). Ti me spent watching TY was significantly associated with higher risk for diab etes. After adjustment for age, smoking, physical activity levels, and othe r covariates, the RRs of diabetes across categories of average hours spent watching TV per week(0-1, 2-10, 11-20, 21-40, and > 40) were 1.00, 1.66, 1. 64, 2.16, and 2.87, respectively (P for trend, < .001). This association wa s somewhat attenuated after adjustment for body mass index, but a significa nt positive gradient persisted (RR comparing extreme categories, 2.31; P fo r trend, .01). Conclusions: increasing physical activity is associated with a significant reduction in risk for diabetes, whereas a sedentary lifestyle indicated by prolonged TV watching is directly related to risk. Our findings suggest the importance of reducing sedentary behavior in the prevention of type 2 diab etes.