Introduction
Child undernutrition is a condition characterised by an inadequate intake of essential nutrients, leading to stunted growth, weakened immune systems and developmental delays.1–3 The WHO classifies nutritional deficiencies into three main anthropometric indicators based on Z-scores derived from the WHO Child Growth Standards: underweight (weight-for-age Z-score (WAZ) <−2 SD), stunting (height-for-age Z-score (HAZ) <−2 SD) and wasting (weight-for-height Z-score <−2 SD).4–11 A Z-score below −2 from the median indicates moderate undernutrition, while a Z-score below −3 SD signifies severe undernutrition. These thresholds serve as key benchmarks for evaluating a child’s nutritional status and guiding appropriate interventions.12 13
Globally, undernutrition continues to impose a substantial burden on young children. Approximately 149 million children under 5 years are stunted and 49.5 million are wasted, accounting for over 45% of the disease burden in this age group.14 In Asia, an estimated 68 million children were stunted as of 2020, closely followed by Africa with 64 million.15 While the prevalence of stunting has declined in Asia (33% to 27%), Latin America (33% to 22%) and Europe (20% to 16%),16–18 chronic undernutrition persists across sub-Saharan Africa (SSA), where approximately 50% of children under 5 are affected. An estimated 21.3% of all children under 5 globally were stunted (144 million), with 36% residing in SSA and Southern Asia, regions that also account for nearly 90% of underweight children worldwide.19–21 Although stunting prevalence in SSA declined from 34.5% in 2012 to 31.1% in 2019, progress has not been sufficient to meet global targets.20
Ethiopia bears one of the highest burdens of child undernutrition globally, with stunting rates of 38%–57%, wasting rates of 10%–17% and underweight rates of 22%–38% among children under 5 years of age.22–24 Ethiopia ranks among eight countries (alongside India, Nigeria, Pakistan, Bangladesh, Indonesia, China and the Democratic Republic of the Congo) that together account for half of all undernourished children worldwide.17 25–29 Child undernutrition in Ethiopia profoundly impacts health, cognitive development, educational outcomes and long-term economic productivity, particularly in low-income settings where access to nutritious food and healthcare remains limited.30 31 In recognition of this burden, Ethiopia has implemented nutrition-specific programmes, including breastfeeding promotion, food accessibility initiatives and the National Nutrition Program (NNP) supported by international partners. However, recent disruptions to external funding, including cuts to United States Agency for International Development, a key supporter of Ethiopia’s NNP and Productive Safety Net Program (PSNP), have endangered nutrition-specific interventions and exacerbated risks for vulnerable populations.32
Existing evidence on child undernutrition in Ethiopia has grown considerably over the past two decades. Studies using the Ethiopian Demographic and Health Survey (EDHS) have documented regional disparities in stunting, underweight and wasting, highlighting rural residence, low maternal education, poverty and poor sanitation as key determinants.22–24 Community-based studies have similarly identified household food insecurity, inadequate complementary feeding and recurrent infections as proximal determinants of undernutrition.30 31 Despite this growing body of evidence, most prior Ethiopian studies have relied on cross-sectional designs, which capture undernutrition at a single point in time and are unable to capture the dynamic trajectories of nutritional status across childhood. Furthermore, the majority of existing analyses have modelled underweight, stunting and wasting as separate outcomes using independent regression models, thereby limiting insight into their longitudinal interplay, particularly how these three indicators co-occur, evolve over time and share common determinants across different stages of child development.
A study conducted in Nigeria addressed this gap partially by applying a multivariate regression model and identifying meaningful associations among the three anthropometric indicators.33 However, it did not explore the long-term consequences of these relationships, nor did it account for the within-child correlations inherent in repeated-measures data. To our knowledge, no prior study in Ethiopia has jointly modelled underweight, stunting and wasting longitudinally while accounting for the correlation structure across multiple time points.
To address this gap, the present study employs a multivariate generalised estimating equations (GEE) approach, which jointly models all three outcomes while explicitly accounting for within-child correlations across repeated measures. Using data from the Young Lives Cohort Survey (YLCS), a longitudinal cohort of 1997 Ethiopian children followed across five time points from ages 1 to 15 years (2002–2016), this study aims to: (1) describe the age-specific prevalence and temporal trajectories of underweight, stunting and wasting across childhood and adolescence in Ethiopia; (2) quantify the co-occurrence and pairwise associations among the three anthropometric outcomes over time and (3) identify child-level, household-level and environmental determinants jointly associated with underweight, stunting and wasting using a multivariate longitudinal framework.
The findings of this study are intended to inform researchers, policymakers and healthcare professionals in designing age-targeted, evidence-based interventions to address the multifaceted and dynamic burden of child undernutrition in Ethiopia.