Estimating the risk of acute malnutrition among under-five children in Uganda: a distributional analysis of socioeconomic and structural inequalities.

BACKGROUND: Under-five undernutrition remains a critical public health challenge, but national averages frequently mask how acute vulnerabilities are socioeconomically and structurally distributed. A distributional epidemiology framework helps isolate actionable entry points for equity-oriented policy. OBJECTIVES: To evaluate the socioeconomic and structural distribution of acute child undernutrition in Uganda and assess aetiological specificity across alternative nutritional outcomes. DESIGN: Secondary analysis of a nationally representative cross-sectional household survey. SETTING: Central, Eastern, Northern and Western regions of Uganda (2019/2020 round). PARTICIPANTS: 815 children aged 24-59 months with complete anthropometric records sampled via a two-stage stratified systematic cluster design. MAIN OUTCOME MEASURES: Childhood wasting (weight-for-height z-score<-2SD) was the primary outcome; chronic stunting and underweight served as specificity checks. Socioeconomic inequalities were quantified using concentration indices. Predictors were modelled using Firth's penalised logistic regression to minimise small-sample bias. RESULTS: Prevalences for stunting, underweight and wasting were 16.9% (n=138), 11.8% (n=96) and 6.1% (n=50), respectively. Macrolevel socioeconomic inequality in wasting was modest and statistically non-significant (Relative Concentration Index=-0.0085, p=0.941). However, sharp structural barriers emerged: children residing ≥4 km from a health facility faced a more than threefold increase in the odds of wasting (adjusted OR (AOR)=3.42, 95% CI 1.01 to 11.54, p=0.048), reflecting an 8.2% absolute risk expansion. This geographic barrier was uniquely specific to wasting. Female children exhibited significantly higher wasting vulnerability (AOR=4.13, 95% CI 1.62 to 10.53, p=0.003; absolute risk increase: 5.0%). Household poverty showed an unexpected inverse trend bordering significance (AOR=0.48, 95% CI 0.21 to 1.09, p=0.080). CONCLUSIONS: Childhood wasting in Uganda is more closely linked to physical access barriers and demographic factors than household asset wealth. Mitigating acute undernutrition requires shifting from wealth-based targeting towards universal structural expansions, specifically prioritising decentralised primary healthcare and gender-sensitive community interventions.