Prevalence, trends and inequalities of childhood undernutrition according to a Composite Index of Anthropometric Failure (CIAF): a systematic review and meta-analysis

Background: The Composite Index of Anthropometric Failure (CIAF) and its extensions-the Composite Index of Severe Anthropometric Failure (CISAF) and extended CIAF (eCIAF)—capture overlapping forms of child undernutrition but remain under-reported at global and regional levels. We aimed to estimate the prevalence of CIAF, CISAF and eCIAF among children under 5 years and assess inequalities by sex, residence, household wealth and maternal education. Methods: We systematically searched major databases, including Embase, MEDLINE (PubMed), Scopus, CINAHL, ProQuest, Global Index Medicus and the Cochrane Library, without language or geographic restrictions. Random-effects meta-analyses estimated pooled prevalence. Heterogeneity was assessed using Cochran’s Q and I² statistics. Subgroup analyses, meta-regression, sensitivity analyses and publication bias assessments were conducted. Inequalities were quantified using prevalence ratios (PRs), prevalence differences, the Concentration Index and the Slope Index of Inequality (SII). Results: We included 107 studies from 18 countries, predominantly low- and middle-income countries in South Asia and Africa (notably India, n=54), comprising over 2.6 million under-5 children for CIAF, 590 744 for eCIAF and 29 905 for CISAF. The pooled prevalence of CIAF was 49.07% (95% CI 46.00% to 52.14%), declining from 59.8% in 2005 to 45.9% in 2024. The pooled prevalence of CISAF and eCIAF was 12.77% and 40.41%, respectively. CIAF prevalence did not differ significantly by sex (pooled PR: 1.04, 95% CI 0.99 to 1.09) but was higher in rural than in urban settings (pooled PR: 1.18, 95% CI 1.10 to 1.27). Substantial socioeconomic inequalities were observed, with higher prevalence among children from the poorest households (pooled PR: 1.71, 95% CI 1.42 to 2.05) and among those whose mothers had no formal education (pooled PR: 1.55, 95% CI 1.26 to 1.90). Absolute inequalities were further confirmed by SII estimates for wealth (−31.28%) and maternal education (−26.60%). Conclusions: CIAF prevalence remains alarmingly high in low-income settings, disproportionately affecting children in rural areas, poorer households and those born to mothers with limited education.