Background:
Obesity prevalence among schoolchildren substantially increases as they move from 1st to 5th grade. School physical activity programs may mitigate the development of obesity, particularly for children from racial/ethnic minorities and low-income households with fewer opportunities to be physically active at home.
Objectives:
This study investigates the relationships between physical activity outside school, physical activity in school and obesity development for a cohort of elementary schoolchildren. Special attention is given to children from racial/ethnic minorities and low-income households who are at higher risk for obesity.
Methods:
We use the Early Childhood Longitudinal Survey (ECLS) for this analysis. Our sample follows a cohort of 9,025 children as they progress from 1st grade to 5th grade (1999-2004). These children are sampled from 940 public and private schools across the United States. Our sample is sufficiently large to study Whites, African-Americans, Asian Americans and Latinos by gender, but not Native American or Pacific Islanders. Child body mass index (BMI) is computed from measured height and weight and children are classified as overweight if BMI exceeds the age- and sex-specific 95th BMI percentile. Measures of physical activity at school include the length of time in recess and physical education (PE) class. Our measure of physical activity outside of school is participation in sports at the local YMCA, church or recreation center. Activities classified as sports include group sports, individual sports, recreational sports, dance, martial arts, playground activities and calisthenics. Measures of after-school physical activity programs are not included in the survey.
Results:
65.9% of children in the sample participate in outside school sports in 4th grade and 49.8% participate in all surveyed years. African Americans and Latinos are significantly less likely to participate in outside school sports as compared to Whites (coefficients = -0.31 and -0.35 respectively, p<0.01). Differences are stronger for females and effects for both genders are modified after controlling for household income. While those not participating in sports outside school may benefit more from school physical activity programs, they are not exposed to more PE time than other children (P<0.05). This finding is consistent in stratifications by race/ethnicity and household income. Differences however are evident for time spent in recess. Children who do not participate in sports outside of school are exposed to about 16 fewer minutes of recess at school. African American and Latino children experience significantly less recess than White children (coefficients = -58.7 and 34.7 minutes respectively, P<0.000). On average, children not participating in sports outside school have a higher BMI percentile and a steeper obesity trajectory as compared to other children in 5th grade. For boys, the BMI percentile gap widens between 3rd and 5th grade while for girls a gap emerges after 1st grade. These patterns are particularly strong for African Americans and Asian girls though interaction effects with household income are not significant (P<0.05).
Conclusions:
African American, Latino and low-income children exhibit lower participation rates in sports outside of school. Furthermore they are exposed to less recess time at school. The period between 1st and 3rd grade appears to be critical for girls, particularly African American and Asian American girls, while between the period between 3rd and 5th grade appears to be critical for boys. Considering participation in outside school sports may better define the role of school programs to mitigate disparities in physical activity and obesity.
Support:
This work is supported by RWJF Active Living Research Grant #61126.
