Two Family Gradients in Children's Physical Activity and Fitness: Socioeconomic Position, Family Structure, and Where They Diverge.

BACKGROUND/

OBJECTIVES

Family circumstances are related to children's physical activity and fitness, yet the two are rarely examined together in the same children. We examined how socioeconomic position and family structure (only-child status) relate to domain-specific reported activity and measured fitness. Socioeconomic position was the mean of maternal and paternal educational attainment, with higher values indicating higher attainment.

METHODS

We designed and conducted a cross-sectional survey of 8228 children in grades 1 to 9 from 27 schools. The questionnaire covered the preceding six months in three domains: physical education class, in-school extracurricular activity and out-of-school exercise. Weekly frequency, duration and intensity were reported for each and summed to weekly moderate-to-vigorous activity (MVPA). Fitness comprised 10 device-measured indicators and, in primary grades, a 5-item motor battery. Linear and logistic models used school fixed effects and school-clustered standard errors, with Benjamini-Hochberg correction.

RESULTS

Median reported weekly MVPA was 300 min; 26.3% of the 7533 children with computable MVPA met the 60 min-per-day guideline. Socioeconomic position was associated with reported MVPA (0.077 SD, 95% CI 0.032 to 0.122) and with meeting the guideline (odds ratio 1.21, 95% CI 1.07 to 1.37). The association appeared in out-of-school exercise but not in physical education class, a contrast of 0.064 SD (95% CI 0.024 to 0.104). Socioeconomic position was also associated with lower handgrip strength (-0.044 SD, 95% CI -0.064 to -0.024) and with more sit-ups in primary grades. Only children showed no clear difference in reported activity in any domain, yet they had lower composite fitness (-0.102 SD, 95% CI -0.142 to -0.061), which remained after adjustment for reported MVPA.

CONCLUSIONS

The socioeconomic gradient in reported activity was concentrated outside the physical education class; family structure was associated with measured fitness without a matching difference in reported activity.