Author

Agnes Bucko

Date of Award

Summer 2022

Document Type

Open Access Dissertation

Department

Exercise Science

First Advisor

Russell R. Pate

Abstract

Sleep and physical activity are both associated with multiple behavioral and metabolic health outcomes, and both behaviors have been linked to the development of weight status. Recent estimates suggest that many children are not meeting sleep recommendations or participating in adequate levels of physical activity, which may be related to the high prevalence of childhood overweight and obesity. Much of the research assessing these relationships has focused on adults and older children, and has relied on parent- or child-reported, cross-sectional research in predominantly White samples. Little work has focused on these relationships in very young children. Although more research has been conducted in adolescent samples, these studies rarely consider the effect of weeknights vs. weekend nights or physical activity intensity in their analyses. Therefore, the overall purpose of this dissertation was to examine the longitudinal relationships between sleep, physical activity, and weight status in both very young children and adolescents.

This dissertation was comprised of three studies. The first study used data from the Linking Activity, Nutrition and Child Health (LAUNCH) observational study to evaluate longitudinal associations between sleep and physical activity in 6-24 month-old children. Device-based measures were used to assess daytime, nighttime, and 24 hour sleep durations, nighttime sleep awakenings, and daytime total physical activity. Linear mixed models assessed whether the within- and between-person effects of physical activity were associated with sleep. Children with higher total physical activity levels slept less during the day compared to children with lower total physical activity levels, and when children were more physically active compared to their own average physical activity levels, their 24-hour sleep duration was lower. Differences in nighttime sleep duration were seen based on race/ethnicity and SES. The findings indicate that mechanisms underlying the sleep and physical activity relationship in young children vary from those that have been suggested in older children and adults.

The second study used data from the LAUNCH observational study to evaluate longitudinal associations between sleep and adiposity in 6-24 month-old children. Device-based measures were used to assess daytime sleep duration, nighttime sleep duration, and daytime total physical activity levels. Diet was assessed via questionnaires completed by the mother. Weight-for-length z-scores were calculated based on measures collected by trained data collectors. Linear mixed models assessed whether the within-and between-person effects of sleep were associated with adiposity. Physical activity and diet were entered into the models as covariates. Children had lower weight-for-length z-scores when they slept less at night compared to their own average nighttime sleep durations, although this relationship was attenuated by daytime physical activity. These associations did not vary based on race/ethnicity, gender, or SES. These results suggest that the relationship between sleep and adiposity is specific to infant’s nighttime sleep durations, and that physical activity has a protective effect on the development of adiposity in very young children.

The purpose of the third study was to assess longitudinal associations between sleep and physical activity in adolescent children who participated in the Next Generations Health (NEXT) Study. Both sleep and physical activity were measured via survey. Surveys asked about weeknight and weekend night sleep separately, and separate questions assessed total physical activity (TPA) and vigorous physical activity (VPA). Linear mixed models assessed whether TPA and VPA were associated with sleep, with separate models created for weeknight and weekend night sleep. For every extra day adolescents met TPA guidelines, they slept 31 minutes less per night on weekend nights. This difference increased by nearly 2 minutes per night for every 1 year increase in age. Adolescents who participated in >7 hours of VPA in the past week slept 216 minutes longer per night on weekend nights than adolescents who did not participate in VPA, and this difference decreased by 13 minutes per night for every 1 year increase in age. Differences in sleep duration were seen based on race/ethnicity, gender, and SES. These findings indicate that both physical activity intensity and day type are important factors to consider when assessing the sleep and physical activity relationship in adolescents.

Although both sleep and physical activity are important behaviors that should be included in interventions targeting obesity prevention, it should be noted that the complex relationships between sleep, physical activity and adiposity in children and adolescents may not follow the same patterns as those seen in adults. This is not surprising considering both sleep and physical activity vary greatly as individuals develop from infancy to adulthood. Furthermore, the differences that were seen in sleep duration by different demographic characteristics suggest that more work is needed addressing the large-scale social determinants of health that are directly related to sleep in order to improve sleep in at-risk populations. Collectively, results from the studies included in this dissertation suggest that future research addressing the relationships among sleep, physical activity, and adiposity should consider physical activity intensity as well as the timing of sleep, whether this be daytime vs. nighttime sleep or weeknight vs. weekend night sleep. Obesity prevention research that focuses on increasing sleep and physical activity must take the age of the children into consideration, as well as demographic characteristics that may play a role in both sleep and physical activity levels.

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