Jessica McNeil1, Nathaniel T. Berry1, Lenka H. Shriver1, Jessica M. Dollar1, Susan P. Keane1, Lilly Shanahan2, Laurie Wideman, FACSM1. 1University of North Carolina at Greensboro, Greensboro, NC. 2University of Zurich, Zurich.

BACKGROUND: There is strong evidence that inadequate sleep (e.g., short sleep duration, poor sleep efficiency) is associated with a greater risk of obesity. Despite significant declines in sleep duration and increases in obesity in emerging adults (ages 18-25 years), data on sleep is scarce in this age group. This study assessed associations between multiple sleep variables, adiposity markers and metabolic hormones in a sample of emerging adults. METHODS: Cross-sectional data in 156 emerging adults (age= 19.4±1.3 years; body mass index (BMI)= 26.0±6.6 kg/m2; sleep duration= 6.0±1.9 hours/day; sleep efficiency= 87.4±4.1%, sleep timing midpoint= 4h51±2h30AM; 58% female; 65% White) from the RIGHT Track Health study were used. Measures included actigraphy-assessed sleep duration (minutes/day), sleep efficiency (sleep duration/time in bed; %), sleep timing midpoint (wake time - ½ sleep duration; clock time), and sleep duration variability (root mean square of sleep duration change across days - mean sleep duration; minutes/day), Bod Pod-assessed adiposity markers (BMI, fat mass index (FMI), fat-free mass index (FFMI) and FM/FFM ratio), and metabolic hormones (insulin and leptin; fasting blood sample). Associations between sleep variables (tertile groups) with adiposity markers and metabolic hormones were assessed with linear regression models adjusted for age, sex, race, and sleep variables (when not the predictor of interest). RESULTS: Compared to the longest sleep duration tertile, individuals with the shortest sleep durations had significantly greater BMI (24.3±5.2 vs. 27.3±7.9 kg/m2; P= 0.03), FMI (6.4±4.3 vs. 8.1±6.5 kg/m2; P= 0.03) and FFMI (β= 18.1±2.3 vs. 19.2±2.8 kg/m2; P= 0.03). Compared to the middle sleep timing midpoint tertile, individuals with a later sleep timing midpoint had significantly lower BMI (27.3±7.9 vs. 24.3±5.4 kg/m2; P= 0.04) and FFMI (19.3±3.1 vs. 18.1±2.2 kg/m2; P= 0.01). No significant associations were noted between sleep efficiency and sleep duration variability with adiposity markers and metabolic hormones. CONCLUSIONS: These results suggest that sleep duration and sleep timing midpoint are associated with adiposity markers in emerging adults. Notably, those with the shortest sleep durations had greater BMI characterized by greater FMI and FFMI, whereas those with the latest sleep timing midpoint had lower BMI characterized by lower FFMI, but not FMI. Grant or funding information: Supported by NIH Grant R01 HD078346-01A1.

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