Current and 1-Year Psychological and Physical Effects of Replacing Sedentary Time With Time in Other Behaviors

Introduction: Sedentary time is inversely associated with health. Capturing 24 hours of behavior (i.e., sleep, sedentary, light physical activity, and moderate-to-vigorous physical activity) is necessary to understand behavior–health associations. Methods: Healthy young adults aged 20–35 years (n=423) completed the Profile of Mood States, the Perceived Stress Scale, and dual-energy x-ray absorptiometry and anthropometric measures at baseline and 12 months. Time spent sedentary (total, in prolonged [>30 minutes] and short [≤30 minutes] bouts), in light physical activity (1.5–3.0 METs), moderate-to-vigorous physical activity (>3.0 METs), and asleep, were assessed through SenseWear armband worn 24 hours/day for 10 days at baseline. Isotemporal substitution modeling evaluated cross-sectional and longitudinal psychological and physical health associations of substituting sedentary time with sleep, light physical activity, or moderate-to-vigorous physical activity. Data were collected from 2010 to 2015 and analyzed in 2019. Results: Cross-sectional analyses revealed substituting prolonged sedentary time for sleep was associated with lower stress (standardized β= −0.11), better mood (−0.12), and lower BMI (−0.10). Substituting total or prolonged sedentary for moderate-to-vigorous physical activity was associated with lower body fat percentage (total, −0.22; prolonged, −0.23) and BMI (−0.40; −0.42). Higher BMI was associated with substituting total or prolonged sedentary for light physical activity (0.15; 0.17); lower BMI with substituting prolonged sedentary for short bouts (−0.09). Prospective analyses indicated substituting total or prolonged sedentary with light physical activity was associated with improved mood (−0.16; −0.14) and lower BMI (−0.15; −0.16); substituting with moderate-to-vigorous physical activity was associated with improved mood (−0.15; −0.15). Conclusions: Short- and long-term psychological benefits may result from transitioning sedentary time to light physical activity or sleep, whereas increasing moderate-to-vigorous physical activity may be required to influence physical health. Trial registration: This study is registered at www.clinicaltrials.gov NCT01746186.