Disentangling the Role of HIV Exposure on Linear Growth Among Mother-Infant Dyads in Western Kenya: A Comparison of Three Growth Models

Abstract

ObjectivesHIV-exposed and uninfected (HEU) infants may experience altered growth compared to HIV-unexposed and uninfected (HUU) infants. Most studies to date have used analytic techniques that do not reflect the dynamic trends in infant growth patterns. We therefore sought to evaluate growth patterns using 3 different analytic methods and examine the role of HIV on growth with each method. MethodsRepeated measures for infant anthropometrics were taken from 6 wk to 23 mo of age in the former Nyanza region, Kenya (n = 310, 52% HEU, 50% male). We used (1) Latent Class Mixed Modeling (LCMM) to identify length-for-age z-score (LAZ) trajectory classes and then multinomial logistic regression to assess how HIV exposure status predicted trajectory class membership, adjusting for covariates (e.g., maternal height, food insecurity); (2) SuperImposition by Translation and Rotation (SITAR) to estimate length in terms of size and velocity (rate of growth) differences by maternal HIV status; and (3) longitudinal regression, the conventional method for analyzing growth, to estimate differences in length and LAZ based on HIV exposure. ResultsAt 6 wks of age, HEU infants had a mean LAZ score of –1.03 ± 1.85 compared to –1.10 ± 1.83 for HUU infants. LCMM identified four LAZ trajectory classes (average 5.1 measurements/infant). Across time, class one LAZ scores remained near 1; class two declined 0 to –1; class three remained near –1; and class four fluctuated between –2 and –3. In logistic regression models, HEU infants were less likely to belong to classes one (RR = 0.3; 95% CI: 0.1,0.9) and two (RR = 0.4; 95% CI: 0.2,0.7) relative to class three. Similarly, SITAR estimated that HEU infants were on average 0.62 cm shorter than HUU infants across the study (95% CI: –1.3,0.1) but there were no differences in mean linear growth velocities. Longitudinal regression models predicted that mean stature for HEU infants was 0.8 cm (95% CI: –1.5, –0.1) shorter and that mean LAZ for HEU infants was 0.4 points (95% CI: –0.7, –0.1) lower compared to HUU infants. ConclusionsAcross the 3 methods, HEU infants were shorter than HUU infants during the first 23 mo of life. Compared to longitudinal regression, advanced modeling with LCMM and SITAR allows for a more flexible assessment of the altered growth patterns HEU infants experience. Funding SourcesNIH.