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Research Project: Childhood Obesity Prevention

Location: Children's Nutrition Research Center

Title: Tests of the disrupted behavioral rhythms hypothesis for accelerated summer weight gain

Author
item Moreno, Jennette - CHILDREN'S NUTRITION RESEARCH CENTER (CNRC)
item Razjouyan, Javad - BAYLOR COLLEGE OF MEDICINE
item Dadabhoy, Hafza - BAYLOR COLLEGE OF MEDICINE
item Reesor, Layton - UNIVERSITY OF HOUSTON
item O'connor, Teresia - CHILDREN'S NUTRITION RESEARCH CENTER (CNRC)
item Hernandez, Daphne - UNIVERSITY OF HOUSTON
item Najafi, Bijan - BAYLOR COLLEGE OF MEDICINE
item Crowley, Stephanie - RUSH UNIVERSITY MEDICAL CENTER
item Alfano, Candice - UNIVERSITY OF HOUSTON
item Thompson, Deborah - Debbe
item Baranowski, Tom - CHILDREN'S NUTRITION RESEARCH CENTER (CNRC)

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 11/1/2017
Publication Date: 4/13/2018
Citation: Moreno, J.P., Razjouyan, J., Dadabhoy, H., Reesor, L., O'Connor, T., Hernandez, D., Najafi, B., Crowley, S., Alfano, C., Thompson, D.J., Baranowski, T. 2018. Tests of the disrupted behavioral rhythms hypothesis for accelerated summer weight gain [abstract]. Society of Behavioral Medicine (SBM) Annual Meeting. April 11-14, 2018; New Orleans, LA. Meeting Symposium.

Interpretive Summary:

Technical Abstract: The school-summer paradigm offers an opportunity to explore school-summer differences in children's behavioral rhythms and their association with seasonal changes in BMI. In the absence of the environmental demands and cues associated with the school year, children's behavioral rhythms (e.g., sleep/wake patterns) may be less stable contributing to misalignment of endogenous circadian rhythms and weight gain. Specifically, during summer children may go to bed later, leading to later bedtime and altered sleep midpoint (a proxy for circadian timing). Later bedtimes may result in shortened total sleep duration due to failure to compensate with a wake time late enough to make up for the later bedtime. A longitudinal observational study involving 119, 5-8 year olds was conducted during the 2016-2017 school year and summer. Sleep timing (phase delay and sleep midpoint) and sleep duration were assessed using Actigraph GT3x-BT monitors worn on the wrist of their non-dominant hand for 8 days during the fall semester and again during the summer when children were not in school. Actilife software, using the Sadeh algorithm, was used to identify sleep epochs. Differences in children’s average bedtime, wake time, sleep midpoint, and sleep duration during the school year and summer were compared using repeated measures ANCOVAs, using BMI percentile as covariate. The effect size (ES) was assessed by Cohen's d and was interpreted as large, medium, or small, if d was greater than 0.8, between 0.5 and 0.8, or less than 0.2, respectively. Significance level was set at p<0.05. 99 participants completed both the school year and summer actigraphy assessment (6.9+/-.85 years, 52% female, 34% overweight). During summer children on average went to bed later (1.8 times = 88min; 95%CI 74.23-102.63, p<0.001, d=1.27) and demonstrated later mean sleep midpoint (29%=82 min, 95%CI 67.68-95.48, p<0.001, d=1.20) compared to the school year. While children exhibited later wake times during summer (14%=75 min, 95%CI 60.13-89.33, p<0.001, d=1.05), they failed to adequately compensate for their later bedtimes, resulting in shortened average sleep duration during summer (3%=15 min, 95%CI 6.20-21.20, p<0.001, d=0.39). During summer, children demonstrated significant changes in their sleep/wake patterns compared to the school year. Our findings provide preliminary support for the disrupted behavioral rhythms hypothesis for accelerated summer weight gain during early elementary school. Future analyses should examine associations between changes in children's behavioral rhythms and seasonal changes in BMI.