Social, economic, and policy environments significantly impact population health and mortality. Demographers and social scientists analyse the levels, heterogeneity, and inequalities in health, ageing, and mortality by examining the interactions among biological, behavioral, social, and environmental factors. This examination spans the entire life course, considers changes over time, and assesses geographical variations. Conversely, population health and mortality play a crucial role in shaping the dynamics of population change, influencing the social, political, economic, and natural landscape.