Chelsea L. SmithƗ1, Emily Gusemanǂ2, Laura Hubbs-Taitǂ3, Jennifer Graefǂ1, Sandra Arnoldǂ1, Allen Knehansǂ1, & Susan B. Sisson ǂ1, FACSM 1University of Oklahoma Health Sciences Center, 2Ohio University, 3Oklahoma State University

Children without siblings, singletons, have higher rates of obesity than children with siblings, non-singletons. Physical activity, such as increased moderate-to-vigorous physical activity (MVPA) and decreased sedentary behavior, can curb excess weight gain early in life.

PURPOSE: The purpose of this study is to examine the differences in physical activity and sedentary behavior between singleton and non-singleton children. METHODS: Mothers of singleton children ages 5.0-7.9 years old and mothers of non-singleton children ages 5.0-7.9 years old with a sibling between the ages of 2.0-4.9 years old in their primary household were recruited. Height, weight, and waist circumference (WC) of child were objectively measured. Mothers reported demographic characteristics of the child and self, and completed a questionnaire on their physical activity. Children wore an accelerometer at the ankle for at least 5 full days while parents recorded daily activities and time spent in away from home care (such as child care or kindergarten). Body mass index (BMI) was calculated, and BMI and WC percentiles were calculated for age and sex. MVPA and sedentary behavior per hour were calculated using accelerometer cut points and total wear time. RESULTS: 40 mother-child dyads (8 singletons and 32 non-singletons) participated. On average mothers were 34.7 years old, employed full time (62%), married (80%), and the child’s biological mothers (97%); while children were 6.16 years old and predominantly white (75%). Singletons had a higher BMI percentile (74.9±19.2) and waist circumference percentile (73.2±19.8) compared to non-singletons (52.9±28.6, p=0.02; 52.8±21.3, p<0.01). In individual models, singletons did not differ in time away from home care (p=0.60) or in their mother’s average MET minutes per week compared to non-singleton children (p=0.90). After adjusting for child BMI percentile and month of wear, singletons spent 3.03 less minutes per hour in MVPA (p<0.01) and 3.98 more minutes per hour in sedentary behavior compared to non-singletons (p=0.01). CONCLUSION: In this sample, singletons had a higher BMI percentile and were less active compared to non-singletons. Investigation into differences in singleton/non-singleton families, including family health behaviors, may support understanding of the mechanism.

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