Later Sleep Timing Predicts Accelerated Summer Weight Gain Among Elementary School Children: A Prospective Observational Study

Authors

Jennette P Moreno
Javad Razjouyan
Houston Lester
Hafza Dadabhoy
Mona Amirmazaheri
Layton Reesor-Oyer
Teresia M O'Connor
Daphne C Hernandez
Bijan Najafi
Candice A Alfano
Stephanie J Crowley
Debbe Thompson
Tom Baranowski

Publication Date

7-12-2021

Journal

International Journal of Behavioral Nutrition and Physical Activity

DOI

10.1186/s12966-021-01165-0

PMID

34247639

PMCID

PMC8273994

PubMedCentral® Posted Date

7-12-2021

PubMedCentral® Full Text Version

Post-print

Published Open-Access

yes

Keywords

Body Mass Index, Child, Child, Preschool, Female, Humans, Male, Schools, Seasons, Sedentary Behavior, Sleep, Weight Gain

Abstract

Objectives and background: Social demands of the school-year and summer environment may affect children's sleep patterns and circadian rhythms during these periods. The current study examined differences in children's sleep and circadian-related behaviors during the school-year and summer and explored the association between sleep and circadian parameters and change in body mass index (BMI) during these time periods.

Methods: This was a prospective observational study with 119 children ages 5 to 8 years with three sequential BMI assessments: early school-year (fall), late school-year (spring), and beginning of the following school-year in Houston, Texas, USA. Sleep midpoint, sleep duration, variability of sleep midpoint, physical activity, and light exposure were estimated using wrist-worn accelerometry during the school-year (fall) and summer. To examine the effect of sleep parameters, physical activity level, and light exposure on change in BMI, growth curve modeling was conducted controlling for age, race, sex, and chronotype.

Results: Children's sleep midpoint shifted later by an average of 1.5 h during summer compared to the school-year. After controlling for covariates, later sleep midpoints predicted larger increases in BMI during summer, (γ = .0004, p = .03), but not during the school-year. Sleep duration, sleep midpoint variability, physical activity levels, and sedentary behavior were not associated with change in BMI during the school-year or summer. Females tended to increase their BMI at a faster rate during summer compared to males, γ = .06, p = .049. Greater amounts of outdoor light exposure (γ = -.01, p = .02) predicted smaller increases in school-year BMI.

Conclusions: Obesity prevention interventions may need to target different behaviors depending on whether children are in or out of school. Promotion of outdoor time during the school-year and earlier sleep times during the summer may be effective obesity prevention strategies during these respective times.