Significant but small: the modest impact of population ageing on reported COVID-19 case rates worldwide

Older adults experienced disproportionate morbidity during the COVID-19 pandemic; however, the independent contribution of population ageing to cross-national variation in reported COVID-19 case rates remains insufficiently examined.

This global ecological study analyzed data from 215 "countries" to assess whether ageing independently predicts COVID-19 case rates, which are influenced by national testing capacity and reporting practices. Confounding variables included economic affluence, the Henneberg Index, urbanization, and vaccination coverage. Analyses comprised bivariate correlations, principal component analysis, and multiple linear regression (enter and stepwise), with subgroup analyses by income level, development status, and World Health Organization region.

Population ageing demonstrated a strong bivariate association with COVID-19 case rates; however, its independent contribution was modest. In adjusted models, population ageing remained statistically significant but explained only 1.7% of the total variance, whereas economic affluence and the Henneberg Index emerged as dominant predictors. The association between ageing and reported case rates was strongest in high-income settings.

Population ageing contributes modestly to cross-national variation in COVID-19 case rates. Broader structural factors and the Henneberg Index play a substantially larger role, underscoring the importance of public health strategies that strengthen surveillance capacity and interpretation of pandemic data at the global level.