0756 Amount and Timing of Sedentary Behavior and Physical Activity following Experimental Sleep Extension in Adolescents

Abstract Introduction Short sleep and sedentary behavior (SB) are both associated with negative health outcomes including increased risk of metabolic syndrome and obesity. Adolescence is a period characterized by decreased physical activity (PA), increased SB, and chronic short sleep. Literature about the impact of sleep duration on PA in adolescents is limited. The goal of this study was to examine changes in the amount and timing of PA and SB following a one-week sleep extension manipulation. Methods The sleep, PA, and SB of 34 short-sleeping (≤7h on school days) and habitually sedentary (< 3h of physical activity per week) healthy-weight adolescents (age=16.4±1.1 years; 68% female; 73% non-Hispanic White) were objectively measured in a randomized cross-over study during the academic year. Participants completed one week of Typical Sleep (usual school schedule) and one week of Sleep Extension (≥1h time in bed each school night). Sleep was estimated using wrist-worn actigraphy; PA and SB were measured using a thigh-worn accelerometer. Paired t-tests compared total minutes and time blocks of PA and SB during each condition. Results Total SB decreased from 750.4±109.08 to 699.32±91.76 min/day during Sleep Extension compared to Typical Sleep (p= 0.018). Specifically, SB significantly decreased during Sleep Extension in the 6PM-12AM (Typical Sleep=223.1±66.6, Sleep Extension=193.8±46.2 min; p=0.04) and 12AM-6AM (Typical Sleep=22.2±36.9, Sleep Extension=5.8±9.5 min; p=0.02) time frames. There were no significant changes in light, moderate, or vigorous PA between conditions (p>0.05). Conclusion Adolescents significantly decreased time spent in SB by nearly 1h per day during Sleep Extension with no change in PA, similar to prior research. Notably, the decrease in SB occurred during the 6PM-6AM time frame, suggesting that the additional sleep displaced time otherwise spent in SB. Reallocation of time spent in SB to PA is associated with positive health outcomes, but no research has examined reallocation to sleep time. Additional studies are needed to identify the related health effects of increased sleep duration and reduced SB in adolescents. Support (if any) NIH NIDDK K23DK117021; NIH BIRCWH 2K12HD057022; CTSA UL1 TR002535