| The first part:Physical activity level and the incidence of diabetes among Chinese adults in urban areas:a prospective cohort studyBackgroundProspective cohort studies conducted in developed countries have reported an inverse association between physical activity and the incidence of diabetes. However, limited data are available from China, the global epicenter of the diabetes epidemic. Therefore, we aimed to examine the association between physical activity level and incident diabetes among Chinese adults in urban areas.MethodsParticipants of the present investigation were from two cohorts:China Multicenter Collaborative Study of Cardiovascular Epidemiology (conducted in1998) and International Collaborative Study of Cardiovascular Disease in Asia (conducted in2000-2001). A total of6348participants aged35to74years who were free of diabetes and cardiovascular disease at baseline were included in our analyses. Baseline physical activity level was estimated based on self-reported overall physical activity on a typical day. According to physical activity level, participants were divided into4groups:"sedentary","low active","active", and "very active". Follow-up study was conducted in2007-2008. The relationship between physical activity level and incident diabetes was examined by Cox proportional hazards regression model. The biological interaction between overweight/obesity and physical inactivity on the risk of developing diabetes was evaluated by additive interaction model.ResultsDuring7.9years of follow-up (50293person-years),478incident cases of diabetes were identified. After adjusting for age, sex, geographic region, educational level, smoking, alcohol use, and family history of diabetes, the hazard ratios (95%CIs) for diabetes across increasing physical activity level groups were1.00(reference),0.82(0.62,1.09),0.63(0.47,0.83), and0.47(0.36,0.61), respectively (P for trend<0.0001). Each10kilo-steps-equivalent increment per day in physical activity volume was associated with a6.2%(95%CI:2.3%,9.9%) reduction in risk of diabetes. The inverse association between physical activity level and risk of incident diabetes was persistent in subgroup analyses according to sex, age, blood pressure, smoking, waist circumference, and fasting blood glucose level. An additive interaction was found between overweight/obesity and physical inactivity on the risk of developing diabetes. The relative excess risk due to interaction was2.36, with an attributable proportion of45%.ConclusionsIncreased physical activity level is associated with substantial reduction in risk of diabetes. Our findings suggest the importance of a physically active lifestyle in the prevention of diabetes. The second part:Association between television viewing time and incident diabetes in Chinese adults:a prospective cohort studyBackgroundProspective cohort studies conducted in western countries have reported that prolonged television watching is associated with elevated risk of diabetes. However, limited data are available from Asia. Therefore, we aimed to examine the association of television viewing time with incident diabetes among Chinese adults.MethodsThis prospective study enrolled a total of8174Chinese adults aged35-74years who participated in the International Collaborative Study of Cardiovascular Disease in Asia in2000-2001. Television viewing time and daily physical activity volume were measured by self-report at baseline survey. Follow-up study on diabetes was conducted in2007-2008. The association of television viewing time with incident diabetes was examined by Cox proportional hazards model.ResultsDuring an average follow up of7.0years (57541.0person-years),548incident cases of diabetes were identified. After adjusting for age, sex, geographic region, educational level, income, smoking, alcohol use, family history of diabetes, and daily physical activity volume, compared with those who watched television0-1h/d, the hazard ratios (95%CIs) of diabetes for participants who watched1.1-2h/d,2.1-4h/d, and>4h/d of television were1.12(0.90,1.40),1.14(0.90,1.44), and1.62(1.14,2.29), respectively. In addition, each1h/d increment in watching television was associated with a9.2%(95%CI:3.1%-15.7%) increase in risk of diabetes. ConclusionsProlonged television viewing time is associated with elevated risk of diabetes. Our findings suggest the importance of less television watching in the prevention of diabetes, especially among those adults who watch television for more than4h/d.
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