title: Stunting Mediates the Association between Small-for-Gestational-Age and Postneonatal Mortality.
abstract: BACKGROUND
  In sub-Saharan Africa, one-third of all births are small for gestational age (SGA), and 4.4 million children are stunted; both conditions increase the risk of child mortality. SGA has also been shown to increase the risk of stunting.
  
  
  OBJECTIVE
  We tested whether the association between SGA and postneonatal mortality is mediated by stunting.
  
  
  METHODS
  We used longitudinal data from children aged 6 wk to 24 mo (n = 12,155) enrolled in the ZVITAMBO (Zimbabwe Vitamin A for Mothers and Babies) trial. HIV exposure was defined based on maternal HIV status at baseline. SGA was defined as birthweight <10th percentile of the INTERGROWTH-21st (International Fetal and Newborn Growth Consortium for the 21st Century) standards. We used a standard mediation approach by comparing the attenuation of the risk when the mediator was added to the model. We used Cox proportional hazards models first to regress SGA on postneonatal mortality, controlling for age. Stunting (length-for-age z score <-2) was then included in the model to test mediation.
  
  
  RESULTS
  Approximately 20% of children were term SGA, and 23% were stunted before their last follow-up visit. In this cohort, 31% of children were exposed to HIV; the HIV-exposed group represented a pooled group of HIV-infected and HIV-exposed but uninfected children. Postneonatal mortality was significantly higher among children born SGA (HR: 1.5; 95% CI: 1.3, 1.7). This association was attenuated and not statistically significant when stunting was included in the model, suggesting a mediation effect (HR: 1.1; 95% CI: 0.91, 1.3). When stratified by HIV exposure status, we observed a significant attenuation of the risk, suggesting mediation, only among HIV-exposed children (model 1, HR: 1.3; 95% CI: 1.1, 1.6; model 2, HR: 1.1; 95% CI: 0.88, 1.3).
  
  
  CONCLUSIONS
  This analysis aids in investigating pathways that underlie an observed SGA-mortality relation and may inform survival interventions in undernourished settings.
authors.affiliation: Departments of International Health and voddo1@jhu.edu.
authors.forename: Vanessa M
authors.initials: VM
authors.lastname: Oddo
authors.affiliation: Departments of International Health and.|Bill & Melinda Gates Foundation, Seattle, WA; and.
authors.forename: Parul
authors.initials: P
authors.lastname: Christian
authors.affiliation: Departments of International Health and.
authors.forename: Joanne
authors.initials: J
authors.lastname: Katz
authors.affiliation: Departments of International Health and.|Population, Family, and Reproductive Health, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD.
authors.forename: Li
authors.initials: L
authors.lastname: Liu
authors.affiliation: Departments of International Health and.
authors.forename: Naoko
authors.initials: N
authors.lastname: Kozuki
authors.affiliation: Departments of International Health and.
authors.forename: Robert E
authors.initials: RE
authors.lastname: Black
authors.affiliation: ZVITAMBO Institute for Maternal and Child Health Research, Harare, Zimbabwe.
authors.forename: Robert
authors.initials: R
authors.lastname: Ntozini
authors.affiliation: Departments of International Health and.
authors.forename: Jean
authors.initials: J
authors.lastname: Humphrey
mesh_terms: D017954:Africa South of the Sahara / Q000453:epidemiology; D001724:Birth Weight; D005260:Female; D005865:Gestational Age; D006130:Growth Disorders; D006801:Humans; D007223:Infant; D007226:Infant Mortality; D007231:Infant, Newborn; D007236:Infant, Small for Gestational Age; D008137:Longitudinal Studies; D008297:Male; D012959:Socioeconomic Factors
keywords: HIV; mediation; postneonatal mortality; small for gestational age; stunting