Life expectancy is a central indicator of population health and socio-economic development. This paper investigates the trends, determinants, and policy implications of life expectancy in Nigeria from 1960 to 2023 using a multilevel theoretical framework and quantitative statistical analysis. Secondary data from the World Bank were employed to analyze the relationship between life expectancy and GDP per capita over six decades. Descriptive statistics, correlation analysis, and regression models were applied. Findings show that while life expectancy increased steadily from 37.2 years in 1960 to 54.5 years in 2023, GDP per capita showed volatility. A time-trend model explained 93% of the variation in life expectancy, compared to 40% explained by GDP per capita. These results underscore that structural, systemic, and syndemic factors beyond economic growth are critical determinants of survival. The study argues for multilevel policy pathways addressing poverty, governance, health systems, and disease clustering to improve life expectancy in Nigeria.