LAUSR

Sleep restriction impairs health, but less is known about the potential health benefits of extending sleep in undergraduate students with habitual short sleep. This study examined the effects of a 1-week, 1-hour per night sleep extension on cardiometabolic health, hydration status, sedentary behavior, and physical activity in undergraduate students. Twelve healthy undergraduate students (83% female; mean±SD age 20.2±1.5; range 18-23 years) obtaining fewer than 7 hours of average nightly sleep completed a two-week study. The first week consisted of sleeping typically ("Habitual"), followed by a peer-delivered intervention to extend time in bed by ≥1 hour/night during the second week ("Extension"). Sleep and physical activity actigraphy were collected throughout. Following each week, participants completed in-person cardiometabolic assessments, including a standardized meal response procedure and blood pressure measurement. Blood samples for measurement of glucose and insulin were collected before, during, and following a standardized breakfast. Urine samples yielded markers of hydration (specific gravity and osmolality). Mixed-effects regression models with random intercepts for individuals compared outcomes after the Extension week to Habitual outcomes. Compared to Habitual sleep, average sleep duration across the Extension week increased (b±SEM, +42.6±.3 minutes; p=.005). After the breakfast meal, glucose area under the curve (AUC; −26.5±10.2 mg/dL*h; p=.025) and time to return to baseline levels (−83.0±46.4 minutes; p=.031) decreased following Extension. There was no change in insulin AUC. Systolic blood pressure decreased (−6.6±2.8 mmHg; p=.037) after Extension. Average time spent in sedentary behavior (−44.3±15.7 minutes; p=.018) and percentage of wake spent in moderate-to-vigorous physical activity (−1%±.4%; p=.030) decreased across the Extension week. Participants who increased average sleep duration ≥15 minutes (n=9) were better hydrated according to urine osmolality (−187.0±68.4 mOsm/kg; p=.026) and specific gravity (−.01±.002 g/mL; p=.012) and had lowered odds of dehydration according to urine osmolality (≥800 mOsm/kg; −67%; OR=.03; p=.035). This pilot study provided evidence that sleep extension may improve cardiometabolic health and hydration and reduce both sedentary behavior and moderate-to-vigorous physical activity. Future research in randomized controlled trials should examine if such findings extrapolate to larger samples and older populations. CRC/CTSI: UL1-TR002014; pilot grant to AMC from the Department of Biobehavioral Health, Pennsylvania State University