Physical activity and risk of type 2 diabetes in a multiethnic cohort in Hawaii

Aim: Incidence rates of type 2 diabetes vary considerably by ethnicity. Physical inactivity is an established risk factor for diabetes; however little is known about this association across ethnic groups with different rates of diabetes. Therefore, we evaluated the association between physical activity and diabetes risk and potential effect modification by ethnicity in the Hawaiian component of the Multiethnic cohort. Methods: From 1993 to 1996, 103,898 subjects (34% Caucasian, 14% Native Hawaiian, 43% Japanese-American) living in Hawaii (USA), aged 45–75 years, were enrolled by completing a questionnaire on demographics, diet, and lifestyle. Information on weekly hours of strenuous sports, vigorous work and moderate activity was assessed. Incident cases of diabetes were identified by self-report, a medication questionnaire, and through record linkage with the major health plans in Hawaii. We performed Cox proportional hazard regression to calculate hazard ratios (HR) and 95% confidence intervals (CI) for diabetes associated with physical activity, adjusted for body-mass-index, ethnicity, education and age. Results: After a mean follow-up time of 13 years, 8587 incident diabetes cases were identified. Engaging in strenuous sports was significantly inversely associated with diabetes risk with adjusted HRs [>4h/week vs. no sports] of 0.67 (CI: 0.57–0.79) in women and 0.79 (CI: 0.71–0.88) in men. Stratified by ethnicity, we found HRs [>4h/week vs. no sports] of 0.54 (CI: 0.38–0.77), 0.65 (CI: 0.47–0.91), and 0.77 (CI: 0.62–0.96) in Caucasian, Native Hawaiian, and Japanese-American women (pinteraction 0.23) and of 0.72 (CI: 0.58–0.89), 0.82 (CI: 0.65–1.04), and 0.85 (CI: 0.73–0.98) in men, respectively (pinteraction 0.05). Vigorous work was inversely associated with diabetes risk in men only, while engaging in moderate activity was inversely associated with diabetes risk only in Caucasian men and women. Conclusion: Our results underline the importance of physical activity in diabetes prevention among men and women of different ethnic backgrounds.