Linear growth through 12 years is weakly but consistently associated with language and math achievement scores at age 12 years in four low- or middle-income countries

Abstract

Background: Whether linear growth through age 12 y is associated with language and math achievement at age 12 remains unclear. Objective: Our objective was to investigate associations of linear growth through age 12 with reading skill, receptive vocabulary, and mathematics performance at age 12 y in four low- or middle-income countries (LMICs). Methods: We analyzed data from the Young Lives Younger Cohort study in Ethiopia (N=1275), India (N=1350), Peru (N=1402), and Vietnam (N=1594). Age 1, 5, 8, and 12 y height-for-age z-scores (HAZ) were calculated. Language and math achievement at age 12 y was assessed using country-specific adaptations of the Peabody Picture Vocabulary Test, the Early Grades Reading Assessment, and a mathematics test; all test scores were standardized by age within country. We used path analysis to examine associations of HAZ with achievement scores. Twelve models were examined at each age (three tests across four countries). Results: Mean HAZ in each country was <-1.00 at all ages. Overall, linear growth through age 12 y was associated with 0.4% to 3.4% of the variance in achievement scores. HAZ at 1 y was positively and significantly associated with the test score in 11 of the 12 models. This association was significantly mediated through HAZ at 5, 8, and 12 y in 9 of the models. HAZ at 5, 8, and 12 y was positively and significantly associated with test scores in 8, 8, and 6 models, respectively. These associations were mediated through HAZ at older ages in 6 of the HAZ at 5 y models and in 6 of the HAZ at 8 y models. Conclusions: Child linear growth between ages 1-12 y was weakly though consistently associated with language and math achievement at age 12 y in four LMICs.