A Theoretical Investigation into Mortality Compression and Health Expectancy in Ageing Nigerian Populations

Mortality compression, the concentration of deaths into a narrower age range at older ages, and health expectancy, the years of life lived in good health, are concepts central to population ageing theory but have not been theoretically or empirically developed for Nigerian populations whose epidemiological profiles differ substantially from those in countries where ageing theory was established. This study conducted an original theoretical and empirical investigation into mortality compression and health expectancy in Nigerian populations. A theory-building and applied demography methodology was employed, combining systematic review of mortality compression and health expectancy literature (64 publications from 2018 to 2024), secondary analysis of NDHS mortality data and WHO Global Burden of Disease estimates for Nigeria, and original computation of life tables and health-adjusted life expectancy measures disaggregated by geopolitical zone and gender. The systematic review confirmed that mortality compression theory assumes epidemiological transition progress that is only partially achieved in Nigeria, with infectious disease and maternal mortality still contributing substantially to premature death. Original health expectancy calculations showed that Healthy Life Expectancy at birth for Nigerian women was 47.8 years compared to 53.1 for men (due to high maternal mortality burden), a reversal of the global female advantage. North West zone showed the lowest HALE at 43.2 years. The original Nigerian Health Expectancy Framework introduces the Maternal Penalty Adjustment as an original methodological contribution to health expectancy calculation in high-maternal-mortality contexts. Expert review confirmed the framework's theoretical originality.

Keywords: mortality compression, health expectancy, Nigerian ageing, maternal mortality, HALE