Child linear growth trajectories during the first three years of life in relation to infant iron status: a prospective cohort study in rural Vietnam

Abstract

Background: Early childhood growth patterns have long-term consequences for health and disease. Little is known about the interplay between growth and iron status during childhood. We explored the interplay between linear growth and iron status during early childhood, by assessing child growth trajectories between 6 and 36 months (m) of age in relation to infant iron status at 6 months of age.

Methods: A cohort study of infants born to women who had previously participated in a cluster randomized controlled trial of antenatal micronutrient supplementation, conducted in rural Vietnam. The relationship between child linear growth trajectories and infant iron status (ferritin concentration) was examined using latent growth curve modeling. Primary outcomes were height for age z scores (HAZ) and growth trajectory between 6 and 36 m of age.

Results: A total of 1112 infants were included in the study. Mean [SD] HAZ scores decreased over time from -0·58 [0·94] at 6 m, to -0·97 [0·99] at 18 m, to -1·14 [0·89] at 36 m of age. There was a steep linear decline in the HAZ scores between 6 and 18 m of age, followed by a slower linear decline from 18 to 36 m of age. Ferritin concentration at 6 m of age was inversely associated with HAZ score at 6 m of age (-0·145, 95% CI [-0.189, -0.101]). There was no association between infant ferritin at 6 m of age and child growth trajectory between 6 and 36 m of age.

Conclusions: Iron status at six months of age did not influence a child's later linear growth trajectory in this cohort of rural Vietnamese children. Longitudinal studies with repeated ferritin and height measurements are required to better delineate this relationship and inform public health interventions.

Keywords: Child; Child growth; Iron; Iron status; Vietnam.

Fig. 1

Flow chart of the infant/child’s participation during 30-months of follow-up. Height for age z-score is considered valid if the data is collected within ± 2·5m visit window

Fig. 2

Individual trajectories, observed mean trend in HAZ scores and stunting prevalence between 6 and 36 months of age (N = 1112). A and B Solid black line represents the mean pattern 6–36 months. B-D HAZ = height-for-age z. D Ferritin concentration tertile at 6 months: 1 ( < 22 ug/L (low)), 2 ( [22, 44] ug/L (mid)), 3 (> 44 ug/L (high))