Growth patterns during the first 12 months of life: post-hoc analysis of South Australian Aboriginal and Caucasian infant data taken from a randomised controlled trial of formula feeding

Abstract

Background and Objectives: To compare growth characteristics of Aboriginal and Caucasian formula-fed infants in the first 12 months of life. Methods and Study Design: We conducted post-hoc data analysis of infants who were part of a previous randomised controlled trial comparing infants randomly assigned to cow or goat milk-based infant formulae. Weight, height, and body composition were assessed at serial time points between study entry (~1-2 weeks of age) and 12 months. There was no growth difference between the randomised groups so the two groups were combined and the data were used to conduct a non-randomised comparison of the growth between Aboriginal (n=11) and Caucasian formula-fed (n=169) infants. Results: Aboriginal formula-fed infants had significantly higher mean z-scores for weight (0.65 difference, [95% CI 0.11, 1.18], p=0.018) and weight-for-length (0.82 difference [95% CI 0.20, 1.44], p=0.010) at 2 months, and all time points onward compared with Caucasian formula-fed infants. Mean length z-scores and the overall growth trajectory across time did not differ between Aboriginal and Caucasian formula-fed infants. Concordant with the weight and weight-for-length z-scores, Aboriginal infants had increased fat mass at 2 months (292 g difference [95% CI 56, 528], p=0.015), and all time points onward compared to Caucasian infants. There was no difference in fat free mass. Conclusions: Though there was only a small number of Aboriginal infants for comparison, our data indicate Aboriginal formula- fed infants were heavier and had a larger increase in fat mass over time compared with Caucasian formula-fed infants. Further studies using a larger cohort are needed to substantiate these findings.