Projecting under-5 mortality in Nigeria using the Arima and Arimax time series models

Abstract

The Nigeria Under-Five Mortality Rate (U5MR) is among the highest globally. In the past few decades, U5MR has consistently declined in Nigeria; however, its pace of reduction is unlikely to meet the global SDGs target by the deadline. Projecting U5MR in Nigeria is essential for health planning and designing a policy framework to further reduce the trend. We projected and examined the potential influence of macroeconomic health financing indicators on U5MR in Nigeria. This retrospective time-series study used World Bank Data from 2000 to 2023. Data were analyzed using ARIMA and ARIMAX time-series models. The data showed a negative association between Out-of-pocket health expenditure (OEX) (coefficient= -1.03, p=0.011) and U5MR. Using the ARIMA model, the U5MR declined from 101.77 per 1,000 live births in 2025 to 60.48 per 1,000 live births in 2039, while the ARIMAX model revealed a decline in U5MR from 99.0 per 1,000 live births in 2025 to 74.1 per 1,000 live births in 2038. In conclusion, the projections of U5MR in Nigeria using ARIMA and ARIMAX are similar, but the ARIMAX model modestly improved predictive accuracy. Prioritizing the expansion of publicly funded health insurance and subsidies to reduce overreliance on out-of-pocket expenditure, especially for vulnerable households, will enable U5MR reduction in Nigeria.