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Title: Tests of the disrupted behavioral rhythms hypothesis for accelerated summer weight gain: Intraindividual variability of children's sleep duration during the school year and summer break

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 AMIRMAZAHERI, MONA - Baylor College Of Medicine
item REESOR, LAYTON - University Of Houston
item WOOD, ALEXIS - Children'S Nutrition Research Center (CNRC)
item HERNANDEZ, DAPHNE - University Of Houston
item NAJAFI, BIJAN - Baylor College Of Medicine
item O'CONNOR, TERESIA - 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: 11/30/2017
Publication Date: 6/4/2018
Citation: Moreno, J.P., Razjouyan, J., Dadabhoy, H., Amirmazaheri, M., Reesor, L., Wood, A.C., Hernandez, D.C., Najafi, B., O'Connor, T.M., Alfano, C.A., Crowley, S.J., Thompson, D.J., Baranowski, T. 2018. Tests of the disrupted behavioral rhythms hypothesis for accelerated summer weight gain: Intraindividual variability of children's sleep duration during the school year and summer break [abstract]. International Society of Behavioral Nutrition and Physical Activity (ISBNPA) Annual Conference. June 3-6, 2018; Hong Kong, China. Meeting Symposium S.43.2.

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 demands of the school year, children's behavioral rhythms (e.g., sleep/wake patterns) may be more variable day-to-day, resulting in greater day-to-day variability of sleep duration and contributing to children’s accelerated summer weight gain. The purpose of the current study was to examine intraindividual variability (IIV) of children's sleep duration during the school year and summer. A longitudinal observational study involving 119, 5-8 year olds was conducted during the 2016-2017 school year and summer. Actigraph GT3x-BT monitors were worn on the wrist of their non-dominant hand, 24 hours a day, for 8 days during the fall semester and again during the summer break. The IIV of sleep duration was assessed using the coefficient of variation (CV). School-summer differences in the CV of overall, weekday, and weekend sleep duration were examined using paired samples t-tests. Effect sizes were 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. A total of 99 participants completed both the school year and summer actigraphy assessments (6.9+/-.85 years, 52% female, 34% overweight). Compared to the school year, during summer children demonstrated greater IIV of overall sleep duration (CVsch=.111, CVsummer=.113; -0.02, 95%CI -0.35¬- -.005, p=.01; d=.37) and weekday sleep duration (CVsch=.098, CVsummer=.124; -.03, 95%CI -.04- -.01; d=.45, respectively). There were no school-summer differences in the IIV of weekend sleep duration (CVsch=.116, CVsummer=.108; .01, 95%CI -.01- .03; d=.12). During summer when children were theoretically allowed to sleep under fewer time constraints, they exhibited greater IIV of sleep duration, especially on weekdays. These results suggest that in the absence of the structure of the school environment, children exhibited greater day-to-day variability of sleep duration, suggesting greater variability in day-to-day behavioral rhythms, possibly contributing to children's accelerated summer weight gain. Future analyses should examine associations between the IIV of children's sleep duration and seasonal changes in BMI.