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Research Project: Preventing the Development of Childhood Obesity

Location: Children's Nutrition Research Center

Title: Seasonality of children's height and weight gain [abstract]

item MORENO, JENNETTE - Children'S Nutrition Research Center (CNRC)
item MUSAAD, SALMA - Children'S Nutrition Research Center (CNRC)
item JOHNSTON, CRAIG - University Of Houston
item BARANOWSKI, TOM - Children'S Nutrition Research Center (CNRC)
item Thompson, Deborah - Debbe
item CROWLEY, STEPHANIE - Rush University Medical Center

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 5/11/2020
Publication Date: 6/2/2020
Citation: Moreno, J.P., Musaad, S., Johnston, C., Baranowski, T., Thompson, D.J., Crowley, S.J. 2020. Seasonality of children's height and weight gain [abstract]. Society for Research on Biological Rhythms (SRBR) Biennial Conference (virtual conference). Poster Presentation.

Interpretive Summary:

Technical Abstract: Studies suggest children increase standardized BMI (BMIz) during summer at a faster rate compared to the school year. This has spurred investment in summertime obesity prevention programs. However, previous studies have largely ignored the impact of seasonality in children's growth patterns. We examined seasonal variation in height and weight gain and its impact on change in BMIz during the summer and school year. Nurses measured heights (cm) and weights (kg) in a cohort of Kindergarteners (n=7599; Ages: 5.7 +/- 0.3, White: 21.1%, Black: 36.2%, Hispanic: 26.0%, Asian 16.7%) twice per year from the beginning of kindergarten through 5th grade (mean dates of assessment: Sept 17 and April 20). Variation in height and weight by season (school year vs summer) was examined using separate mixed effects models. Season, sex, and ethnicity were tested as fixed effects. Random effects included repeated measurements of time, students nested within school, intercept, and slope for growth over time. Similar models used BMIz as the outcome, examined the interaction of height or weight with season. A Bonferoni correction was applied to control for 3 different analyses (p<.016). The rate of height gain was greater during the school year (~Sept to April) compared to summer (~April to Sept) (Beta=-0.05, SE=.014, p=0.0004). Compared to whites, Hispanic children gained less height during the school year (Beta=-.09, SE=.02, p<.0001) and Asian children gained less height during the summer (Beta=-.07, SE=.02, p<.0001). Rate of weight gain did not differ seasonally. Height gain was more strongly associated with increased BMIz during summer compared to the school year (Beta=.03, SE=.002, p<.0001), especially among Hispanics (Beta=.014, SE=.004, p=.0031) and white children (Beta=.02, SE=.004, p=<.0001). School-summer variability in BMIz was accounted for by seasonal variability in height rather than weight. These results support delivery of obesity prevention programs year round, not just during summer. Future research with more frequent measurements is needed to better understand seasonal regulation of children's growth. The potential impact of seasonal changes to photoperiod within time zones and in the context of our modern lighting environment may also need consideration.