Sex Differences in Early Childhood Growth in a Resource-limited Setting: A Secondary Analysis of the Early Life Interventions in Childhood Growth and Development In Tanzania (ELICIT) Study.

Abstract

BACKGROUND\nIn population-based growth surveys in sub-Saharan Africa, boys have higher rates of growth failure than girls.\n\n\nOBJECTIVE\nOur goal was to assess for the presence, timing and potential etiology of sex-based differences in length-for-age z-score (LAZ), weight-for-age z-score (WAZ) and head-circumference-for-age z-score (HCZ) in a birth cohort in rural Tanzania.\n\n\nMETHODS\nWe performed a secondary analysis of RCT data on 1084 children followed from age\xa0<\xa02\xa0weeks-18 months, assessing anthropometry (measured every 3-months), illness (hospitalization and monthly maternal report of symptoms) and feeding (monthly maternal report of exclusive breastfeeding [EBF] and complementary solids and liquids [CSL]). We used linear regression to assess sex differences in LAZ, WAZ and HCZ over time.\n\n\nRESULTS\nWhile male and female infants had similar anthropometry measures at study entry, males exhibited poorer growth through 6-months (e.g., 3-month mean LAZ: males -0.94, females -0.74, P\xa0<\xa00.01; 3-month mean WAZ: males -0.63, females -0.48, P\xa0<\xa00.05), without significant worsening from 6-18 months. Males had lower HCZ only at 9-months. In evaluating possible etiologies, mediation analysis failed to identify illness or hospitalization as mediators of poorer growth among males, though at age 3-months, males with recently-reported illness exhibited greater decline in WAZ than females with illness (ΔWAZ: males -0.24, females 0.03, heterogeneity test P\xa0=\xa00.01). Differences in EBF and introduction of CSL did not explain the sex-based growth outcomes.\n\n\nCONCLUSIONS\nIn longitudinal analysis, males exhibited more severe growth failure by 3-months than girls and did not exhibit catch-up growth between 6-18 months. Reported symptoms of illness and early introduction of CSL did not appear to be mediators of these sex-based differences, though likely not all sickness was captured by monthly maternal report. Given the early nature of these deficits, LAZ and WAZ measures at 6-months may be good outcomes for intervention studies targeting improvements in early childhood growth and thriving.