Abstract
To investigate the prevalence and socio-economic inequalities in breast milk, breast milk substitutes (BMS) and other non-human milk consumption, by children under 2 years in low- and middle-income countries (LMIC). We analysed the prevalence of continued breast-feeding at 1 and 2 years and frequency of formula and other non-human milk consumption by age in months. Indicators were estimated through 24-h dietary recall. Absolute and relative wealth indicators were used to describe within- and between-country socio-economic inequalities. Nationally representative surveys from 2010 onwards from eighty-six LMIC. 394 977 children aged under 2 years. Breast-feeding declined sharply as children became older in all LMIC, especially in upper-middle-income countries. BMS consumption peaked at 6 months of age in low/lower-middle-income countries and at around 12 months in upper-middle-income countries. Irrespective of country, BMS consumption was higher in children from wealthier families, and breast-feeding in children from poorer families. Multilevel linear regression analysis showed that BMS consumption was positively associated with absolute income, and breast-feeding negatively associated. Findings for other non-human milk consumption were less straightforward. Unmeasured factors at country level explained a substantial proportion of overall variability in BMS consumption and breast-feeding. Breast-feeding falls sharply as children become older, especially in wealthier families in upper-middle-income countries; this same group also consumes more BMS at any age. Country-level factors play an important role in explaining BMS consumption by all family wealth groups, suggesting that BMS marketing at national level might be partly responsible for the observed differences.
Highlights
In low-income countries, formula and other types of milk are used by similar proportions of children at birth, but formula consumption remains stable at very low levels throughout the age range under study, whereas other milks increase in frequency up to around 12 months, remaining stable thereafter
In all groups of countries, other milks are more frequently used than formula and less than half of children were breastfed at 24 months of age
We further explored the heterogeneity among countries using multilevel analyses, with countries representing the first level and log household income per quintile within each country in the second level (Table 1). In this type of analysis, it is common to observe that the higher level variable - countries - explains a small proportion of the overall variance. We found that this level explained nearly 30 % of the variance in infant formula consumption under 6 months and of continued breast-feeding at 1 year, suggesting the existence of country characteristics that markedly influence feeding patterns by all groups of wealth, which deserve more in-depth analysis in the future
Summary
We sourced data from nationally representative crosssectional surveys conducted periodically in LMIC, namely Demographic Health Surveys[9] and Multiple Indicator. These surveys cover a large number of reproductive, maternal, newborn and child health indicators, employing multistage sampling strategies to collect household-level data. We selected the most recent publicly available survey for each country carried out since 2010. In both types of surveys, face-to-face interviews were performed through standardised questionnaires, so that both types of surveys are highly comparable[11]. We included the nationally representative surveys conducted in Ecuador and Peru, after harmonisation of its data set and variables in accordance with the Demographic Health Surveys/Multiple Indicator Cluster Surveys standards[14,15]
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