Physical Activity and Television Watching in Relation to Risk of Type 2 Diabetes: The Black Women's Health Study

Few modifiable risk factors for type 2 diabetes have been documentedin the high-risk population of US black women. The authors useddata from 45,668 black women aged 21–69 years, followedbiennially from 1995 to 2005 in the Black Women's Health Study,to estimate incidence rate ratios for type 2 diabetes comparingvarious levels of physical activity and television watching.Cox proportional hazards models were used to control confoundingfactors. During 10 years of follow-up, 2,928 incident casesof type 2 diabetes were identified. Vigorous activity was inverselyassociated with type 2 diabetes risk (P_trend < 0.0001); theincidence rate ratio for 7 hours per week was 0.43 (95% confidenceinterval (CI): 0.31, 0.59) relative to no activity. Brisk walkingfor 5 hours per week was associated with reduced type 2 diabetesrisk (incidence rate ratio = 0.67, 95% CI: 0.49, 0.92) relativeto no walking. Television watching was associated with an increasedtype 2 diabetes risk: The incidence rate ratio was 1.86 (95%CI: 1.54, 2.24) for 5 hours relative to <1 hour of televisionper day, independent of physical activity. These observationaldata suggest that black women might reduce their risk of developingtype 2 diabetes by increasing their time spent walking or engagedin vigorous physical activity and by limiting television watching. African continental ancestry group; diabetes mellitus, type 2; exercise; incidence; motor activity; television; walking; women's health