Trends and Determinants of Infant and Under-Five Mortality in Nigeria: A Subnational Analysis of Three Decades of Demographic and Health Survey Data (1990–2024)

Abstract

Nigeria records one of the world's highest absolute numbers of child deaths. National averages obscure significant variation across its 36 states and Federal Capital Territory (FCT), demanding subnational evidence to achieve Sustainable Development Goal (SDG) 3.2. To examine subnational trends in infant (IMR) and under-five mortality rates (U5MR) in Nigeria (1990–2024), and quantify associations between child mortality and three determinants: maternal secondary education, health-facility delivery, and full basic vaccination coverage. An ecological analysis of Demographic and Health Survey data (1990–2024) was conducted. Zone- and state-level estimates were extracted for mortality rates, facility delivery, vaccination, and maternal education. Analysis included descriptive trends, comparisons against the SDG 3.2 target (U5MR ≤25), Pearson correlation, and multiple linear regression using 2024 data. Findings show that National U5MR declined 57% (193 to 82 per 1,000 live births) from 1990–2024, while IMR fell 46% (92 to 50). Progress was highly uneven: 2024 U5MR in the South West (42) was a third of the North West's (140). Only four states (Kwara, Ondo, Edo, Oyo) met the SDG 3.2 target, whereas five northern states (Jigawa, Kebbi, Kano, Gombe, Kaduna) recorded U5MRs above 150. State-level U5MR correlated negatively with maternal education (r=−0.70), facility delivery (r=−0.72), and vaccination (r=−0.33). Education and facility delivery jointly explained 56% of U5MR variance. The paper concludes that despite substantial reductions since 1990, Nigeria will miss SDG 3.2 without accelerating progress in northern states. Expanding girls' education, facility deliveries, and targeted immunization in the north represent the highest-leverage priorities.