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Title: The transition from the school year to summer environment and impacts on children's sleep/wake rhythms and weight gain

Author
item MORENO, JENNETTE - Children'S Nutrition Research Center (CNRC)
item RAZJOUYAN, JAVAD - Baylor College Of Medicine
item DADABHOY, HAFZA - Children'S Nutrition Research Center (CNRC)
item ALFANO, CANDICE - University Of Houston
item CROWLEY, STEPHANIE - Rush University Medical Center
item Thompson, Deborah - Debbe
item BARANOWSKI, TOM - Children'S Nutrition Research Center (CNRC)

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 11/1/2018
Publication Date: 3/9/2019
Citation: Moreno, J.P., Razjouyan, J., Dadabhoy, H., Alfano, C.A., Crowley, S.J., Thompson, D.J., Baranowski, T. 2019. The transition from the school year to summer environment and impacts on children's sleep/wake rhythms and weight gain [abstract]. Society of Behavioral Medicine (SBM) Annual Meeting. March 6-9, 2019; Washington, DC. Meeting Symposium.

Interpretive Summary:

Technical Abstract: During summer, children gain weight at accelerated rates compared to the school year, contributing to increases in the prevalence of overweight and obesity among children. It is hypothesized that the transition from the school year to summer environment results in a change in social demands leading to changes in social rhythms or routines and increasing the variability of children's sleep/wake patterns especially on weekdays. Frequent changes in sleep/wake patterns may result in a chronic state of desynchronization, leading to accelerated weight gain. The purpose of the current study was to examine the relationship between variability in children's weekday sleep/wake patterns during the school year and summer among 5-8 year-old children and the association with BMI and change in BMI during the school year and summer. Sleep, rest/activity, and light exposure patterns were measured for 8 days using wrist actigraphs in 119 elementary school children aged 5 to 8 years during the school year and summer. Sleep onset and offset were determined using the sadeh algorithm and sleep diaries, from which the midpoint of sleep was calculated. Variability was assessed using the root mean square of successive night differences. BMI was assessed at the beginning and end of the 2016-2017 school year and end of the 2017 summer vacation. Children gained weight at a faster rate during summer compared to the school year (.04 +/- .18; p=.032, 95% CI: .003-.07). The night-to-night variability of weekday sleep midpoint increased by 19 minutes (+/- 31 minutes; p<.001, 95% CI: 13.3-25.6) during summer. Night-to-night variability of weekday sleep midpoint did not predict change in BMI during the school year or summer (B=.00, SE=.00, R2=.001, ns and B=.00, SE=.00, R2=.007, ns). However, cross-sectionally, greater night-to-night variability in weekday sleep midpoint during summer predicted having a higher standardized BMI at the end of the summer (B=.008, SE=.004, R2=.05, p=.025) while school year variability did not predict baseline BMI (B=.002, SE=.004, R2=.002, ns). The school year promoted more consistent timing of sleep on weekdays and a slower rate of weight gain compared to the summer. Cross-sectionally, greater night-to-night variability during summer was associated with greater BMI, but did not predict change in BMI, limiting our ability to draw conclusions about causality. These findings are consistent with studies among adults indicating an association between BMI and night-to-night variability in the timing of sleep, yet the directionality of this relationship remains to be determined.