Association between birth length, linear growth velocities, and primary school achievement at age 10 years: evidence from the Ethiopian iABC birth cohort.

BACKGROUND

Childhood is a period marked by dynamic growth. Evidence of the association between childhood linear growth and school achievement comes mostly from cross-sectional data. We assessed associations between birth length, childhood linear growth velocities, and stunting with school achievement.

METHODS

Newborns were recruited into the Ethiopian infant Anthropometry and Body Composition (iABC) birth cohort and followed from birth to 10 years. Velocities from 0 to 6 years were computed using linear spline mixed effect modelling. Stunting (height-for-age < -2 z-scores) was assessed at the ages of 1, 2, 4, 5, and 6 years. School achievement was measured by having a high (≥ 80%) combined high math, English, and science (MES) score and being at appropriate grade-for-age. Logistic regression models assessed associations between birth length, linear growth velocities and stunting with school achievement.

RESULTS

Children's mean age was 9.8 years (standard deviation, SD 1.0, range 7-12 years). A 1 SD greater birth length increased the odds of achieving a high MES combined score by 1.42 (95% CI: 0.99, 2.03). A 1 SD increase in linear growth velocity from 6 to 24 months increased the odds of being in the appropriate grade-for-age by 1.66 (95% CI: 1.14, 2.43). Stunting at ages 4 and 6 years was associated with lower odds of achieving a high MES combined score: 0.43 (95% CI: 0.20, 0.93) and 0.31 (95% CI: 0.11, 0.89), respectively. Faster post-natal linear growth was not associated with school achievement.

CONCLUSION

Greater birth length and higher growth velocity from 6 to 24 months were associated with higher school achievement and being in the appropriate grade-for-age, respectively. Children who experienced growth failure were less likely to achieve a high MES score. Interventions aimed at improving school achievement should address maternal and fetal nutrition and health, and monitor post-natal growth.