Abstract MP45: Social Jetlag, Independent Of Other Sleep Characteristics, Is Associated With Obesity-related Outcomes In 9-11-year-old Girls

Abstract

Introduction: Though short sleep has been identified as a predictor of childhood obesity, few have explored the importance of sleep characteristics beyond duration. Literature in adolescents examining the influence of social jetlag, the difference in hours between the midpoint of sleep during weekdays (school) and weekend days (free), has suggested a potential sex-specific relationship with obesity-related indices. However, little is known about the potential sex-specific relationships between social jetlag or other sleep characteristics and obesity-related outcomes earlier in youth. Objective: To examine the relationships between sleep duration, disturbances, and social jetlag with obesity-related outcomes during childhood, with an emphasis on sex-specific relationships. Methods: This cross-sectional study included 381 children from Dunedin, New Zealand (9-11 years, 49.6% female). Average sleep duration, social jetlag, and physical activity were assessed via wrist-worn accelerometry, measured over 8 consecutive days. Sleep disturbances were quantified from the Children's Sleep Habits Questionnaire, with higher scores (range 1-3) denoting more frequent sleep disturbances. Obesity-related outcomes included age-specific body mass index z-scores (zBMI) calculated using the World Health Organization method, relative (% fat) and absolute (kg) adiposity and fat mass index (kg/m 2 ) assessed via bioelectrical impedance analysis, and waist-to-height ratio (WHtR). Linear mixed models that nested children within schools, with a random intercept and fixed slope were used to identify relationships among sleep variables and obesity-related outcomes. Multivariable analyses included all sleep variables (unadjusted) and known covariates (adjusted). Cross-level interactions assessed the presence of sex-specific relationships. Results: Positive associations between social jetlag with zBMI, % fat, and fat mass index were seen in univariable and unadjusted multivariable analyses. Associations between sleep duration and sleep disturbances with body composition variables were non-significant. Following adjustments for known confounders, social jetlag remained significantly associated with zBMI ( B =0.23, 95%CI: 0.03, 0.43, p =0.025), though not with any other obesity-related outcome. Furthermore, cross-level interactions were present for social jetlag with zBMI ( B =-0.40, 95%CI: -0.80, -0.00, p =0.051) and LnWHtR ( B =-0.01, 95%CI: -0.03, -0.00, p=0.042), with simple slopes suggesting positive associations in girls but not boys (girls B =0.43 and 0.01, respectively, both p <0.05 ). Conclusions: Social jetlag may be an important target for youth obesity prevention efforts, given its association with obesity-related outcomes. Importantly, these associations were seen in girls but not boys, suggesting that a targeted approach to prevention may be needed.