Spatial heterogeneity and co-occurrence of childhood undernutrition in India: a joint analysis of stunting, anaemia and low birthweight.

BACKGROUND: Childhood undernutrition remains a major public health challenge in India, with high prevalence of stunting, anaemia, and low birthweight. These conditions often co-occur within populations but are typically analysed in isolation, leading to an incomplete understanding of their joint burden and spatial distribution. This study aims to examine the co-occurrence, spatial heterogeneity, and associated risk factors of these three indicators using a unified analytical framework. METHODS: We used nationally representative data from the National Family Health Survey (2019-2021) covering 104,021 children aged 0-59 months. A joint modelling framework based on a trivariate Gaussian copula was employed to simultaneously analyse stunting, anaemia, and low birthweight while accounting for their interdependence. The models incorporated child, maternal, and household-level covariates, along with non-linear effects and spatial components to capture geographic variation across states and union territories of India. RESULTS: The prevalence of stunting, anaemia, and low birthweight was 35.4%, 67.5%, and 16.1%, respectively. Significant positive associations were observed between each pair of conditions. Maternal and household characteristics-including maternal nutritional status, prenatal care, education, and socioeconomic status-were strongly associated with all three outcomes. Substantial spatial heterogeneity was observed in both the individual prevalence and joint burden of these conditions. In addition, the strength of association between outcomes varied across regions, indicating context-specific patterns of co-occurrence. CONCLUSIONS: Childhood undernutrition in India is characterized by both high co-occurrence and marked spatial heterogeneity. The findings highlight the need for integrated and geographically targeted public health interventions that address multiple dimensions of undernutrition simultaneously, rather than relying on single-outcome approaches.