Polluted air and fading memory: Effects of air pollution on Alzheimer's disease and vascular dementia.

Air pollution is widely recognized as a major public health concern, and emerging evidence suggests an association with dementia. Establishing a causal relationship, however, is difficult. Economic cycles affect both dementia prevalence and pollution levels: during economic booms, financial resources for treatment rise, but so do air pollution and work-related stress. In South Korea, air quality has generally improved, even as Alzheimer's cases have increased with population aging, indicating a time-series relationship that biases regression results. Air pollution and vascular dementia also temporarily declined during COVID-19, reflecting omitted variable bias. To address these endogeneity concerns, we use wind speed and direction as instruments for air pollution in South Korea. Our estimates show that higher concentrations of PM10, PM2.5, and NO2 significantly increase dementia cases, with instrumental variable results substantially larger than ordinary least squares, underscoring the importance of correcting for bias. These findings carry important policy implications. Because air pollution is a negative externality, its health consequences-including dementia-extend beyond individual responsibility and represent broader social costs. Reducing pollution could therefore not only improve health outcomes but also ease the considerable economic burden of dementia care. As air pollution disproportionately affects vulnerable groups-individuals with dementia who are unable to sustain employment or income-targeted social support is also essential to address their combined medical and financial challenges.Implications: We underscore the importance of addressing endogeneity issues when evaluating the relationship between air pollution and dementia. Conventional approaches may produce biased estimates due to spurious time-series-correlations and omitted variables. By using wind speed and direction as instruments, we identify LATE-based causal effects of air pollution on the number of dementia patients. Our findings suggest important policy implications: reducing air pollution can lower the substantial social and economic costs associated with dementia. Improved administrative data linking clinical records with environmental exposures would support effective monitoring and policy evaluation. Furthermore, international cooperation is needed to address transboundary nature of air pollution.