Longitudinal associations between weight status and academic achievement in primary school children

The Cross-Sectional and Longitudinal Association Between 24-Hour Movement Behavior Compositions With Body Mass Index, Waist Circumference, and Internalizing and Externalizing Symptoms in 6-Year-Old Children

BACKGROUND

Few studies have examined the association between 24-hour movement behaviors and health in children in their first 2 years of primary school. This study aimed to examine how 24-hour movement behavior compositions at age 6 were related to body mass index (BMI), waist circumference, and internalizing and externalizing symptoms at ages 6 and 10.

METHODS

A subsample of 361 children from the HealthNuts cohort study with valid accelerometer data was included in the cross-sectional analysis. Of these, 279 had longitudinal data for social-emotional outcomes and 113 had longitudinal anthropometric data. Children's 24-hour movement behaviors (ie, sleep, sedentary time, light-intensity physical activity, and moderate- to vigorous-intensity physical activity [MVPA]) were assessed over 8 days using accelerometery and activity logs. BMI z score and waist circumference were assessed using standardized protocols, and parents reported on their child's internalizing and externalizing behaviors. Cross-sectional and longitudinal associations were estimated using compositional data analysis and compositional isotemporal substitution analysis.

RESULTS

Overall, 24-hour movement behaviors were significantly related to internalizing symptoms cross-sectionally and longitudinally and BMI z-score cross-sectionally. Results from compositional isotemporal substitution models indicated that replacing sedentary time or light-intensity physical activity with MVPA was associated with fewer internalizing symptoms at ages 6 and 10. Replacing time spent sedentary and in light-intensity physical activity or MVPA with sleep was associated with lower BMI z score at age 6.

CONCLUSION

Spending more time in MVPA relative to other movement behaviors is associated with fewer internalizing symptoms. In additional, spending more time sleeping is associated with lower BMI z score and waist circumference in children.

Untangling the relationship between BMI and academic achievement in the elementary years

Although the negative relationship between BMI and academic achievement (AA) is well documented, no prior studies have investigated the potential bi-directional relationship between BMI and AA in childhood. We investigated the longitudinal relationships between child BMI and AA across different school subjects (reading, math and science) and sexes. To do so, we employed the Early Childhood Longitudinal Study kindergarten cohort (2011), which is a nationally representative sample of American children who entered kindergarten in 2010-2011. We utilised the kindergarten-fifth grade longitudinal sample (n 17 480) and applied cross-lagged panel models with fixed effects to address unobserved heterogeneity. Our results showed significant but small reciprocal relationships between BMI and math/science achievement for girls (n 8540) (year-to-year effect sizes ranged from -0·01 to -0·04), but not for reading. In contrast, we did not find any evidence of reciprocal relationships between BMI and AA for boys (n 8940). Our results reveal that early weight status and academic performance may be jointly responsible for a vicious cycle of poor AA and unhealthy weight. Breaking the cycle from AA may complement existing obesity prevention strategies, particularly for girls in the science, technology, engineering and mathematics field.