Survival analysis of maternal, household, environmental, and child-level determinants of under-five mortality in Nigeria

In Africa, Nigeria bears the highest burden of under-five mortality, with an estimated 850,000 under-five deaths from preventable causes reported in 2024. Existing evidence has not applied a time to event approach using recent nationwide data to examine factors associated with child mortality in this high-burden setting. The current study employed a time to event approach to examine factors affecting under-five mortality across a 59-month life course. Retrospective data from the 2024 Nigeria Demographic and Health Survey was used. We analyzed data for 27,604 under-fives. Descriptive statistics, Kaplan-Meier survival estimates and Cox proportional hazards model were performed to determine the time to death. Of the 27,604 under-five children included, 7.97% had died. Nearly half (47.8%) of deaths occurred within the first 28 days of life. Adjusted results showed that multiple births increased under-five mortality (AHR = 5.51, 95% CI: 4.70–6.46; p = 0.001), whereas longer birth intervals reduced risk (AHR = 0.11–0.73; p = 0.001). High birth order increased mortality (AHR = 1.92, 95% CI: 1.10–3.36; p = 0.022). Maternal post-secondary education (AHR = 0.70, 95% CI: 0.55–0.90; p = 0.005), delayed first birth (AHR = 0.87, 95% CI: 0.79–0.97; p = 0.012), and residence in southern regions were protective, whereas rural residence (AHR = 1.23, 95% CI: 1.09–1.38; p = 0.001) and lack of mosquito nets (AHR = 1.82, 95% CI: 1.61–2.06; p = 0.001) increased mortality. Under-five mortality is highest in the neonatal period and is shaped by birth spacing, multiple births, and inequality. Improving early interventions, optimal spacing, and reducing regional disparities are key to improving child survival.