Prospective associations of occupational and leisure-time physical activity with risk of diabetes: a cohort study from the United States

OBJECTIVES: Leisure-time physical activity (LTPA) can reduce the risk of incident diabetes, whereas the role of occupational physical activity (OPA) in developing diabetes is still unclear due to conflicting evidence. Moreover, the joint associations of OPA and LTPA with incident diabetes among US workers have not yet been systematically examined. The objective of this study was to assess the independent and joint associations of OPA and LTPA with incident diabetes. METHODS: This prospective cohort study included 1406 workers free from diabetes at baseline (2004-2006) from the national, population-based Mid-life in the United States (MIDUS) study. Associations of OPA and LTPA at baseline with incident diabetes during 9 years of follow-up were examined using Poisson regression models. High OPA was defined based on engagement in physical demands at work, and high LTPA was defined as participation in moderate or vigorous LTPA at least once per week. RESULTS: High OPA was associated with an increased risk of diabetes compared to low OPA (adjusted risk ratios and 95% confidence interval = 1.52 [1.04, 2.22]), while high LTPA was associated with a decreased risk of diabetes compared to low LTPA (0.66 [0.44, 0.97]). Diabetes risk was the highest among workers with high OPA and low LTPA (2.30 [1.30, 4.07]). CONCLUSIONS: In a national, population-based prospective cohort study of US workers, high OPA was associated with an elevated risk of diabetes, while high LTPA was associated with a decreased diabetes risk. The combination of high OPA and low LTPA exhibited the greatest risk of diabetes.