Aims/hypothesis: The Diabetes Prevention Program (DPP) lifestyle intervention successfully achieved its goal of increasing leisure physical activity levels. This current study examines whether the lifestyle intervention also changed time spent being sedentary and the impact of sedentary time on diabetes development in this cohort.
Methods: 3,232 DPP participants provided baseline data. Sedentary behaviour was assessed via an interviewer-administered questionnaire and reported as time spent watching television specifically (or combined with sitting at work). Mean change in sedentary time was examined using repeated measures ANCOVA. The relationship between sedentary time and diabetes incidence was determined using Cox proportional hazards models.
Results: During the DPP follow-up (mean: 3.2 years), sedentary time declined more in the lifestyle than the metformin or placebo participants (p < 0.05). For the lifestyle group, the decrease in reported mean television watching time (22 [95% CI 26, 17] min/day) was greater than in the metformin or placebo groups (p < 0.001). Combining all participants together, there was a significantly increased risk of developing diabetes with increased television watching (3.4% per hour spent watching television), after controlling for age, sex, treatment arm and leisure physical activity (p < 0.01), which was attenuated when time-dependent weight was added to the model.
Conclusions/interpretation: In the DPP, the lifestyle intervention was effective at reducing sedentary time, which was not a primary goal. In addition, in all treatment arms, individuals with lower levels of sedentary time had a lower risk of developing diabetes. Future lifestyle intervention programmes should emphasise reducing television watching and other sedentary behaviours in addition to increasing physical activity.
Trial registration: ClinicalTrials.gov NCT00004992.