Early-Life Exposure to Air Pollution and Cognitive Decline: The Role of Socioeconomic Status as a Confounder

Early-life Exposure to Air Pollution and Cognitive Decline: The Role of Socioeconomic Status
as a Confounder
Ciara Harkin
Chair of Supervisory Committee:
Joan Casey
Department of Environmental and Occupational Health Sciences
Department of Epidemiology
Background: Cognitive decline and dementia are major public health concerns as the U.S.
population ages. Identifying early-life environmental risk factors may clarify life course
determinants of dementia.
Methods: We linked Health and Retirement Study (HRS) participants (n = 6571) to their county
of residence in the 1940 U.S. Census and estimated early-life exposures to ambient and sourcespecific air pollution. Exposures included residential proximity to fossil fuel power plants, oil
and gas wells, automobile emissions, and all-source fine particulate matter (PM2.5). Predicted
dementia probability was derived from validated HRS algorithms between 2000–2020. We fit
generalized linear mixed-effects models and random subject intercepts, stratified by individuallevel race (i.e., Black or White), to estimate associations between exposures and dementia probability trajectories. Models were sequentially adjusted for demographics, early-life
socioeconomic conditions, and county-level contextual covariates.
Results: In time-on-study models, no consistent associations were observed between early-life
exposure to power plant emissions, oil and gas well density, or automobile emissions and
predicted probability of dementia. Higher early-life PM₂.₅ concentrations were modestly
associated with increased dementia probability, though estimates attenuated following
adjustment for socioeconomic covariates. Analyses stratified by race revealed generally higher
dementia risk among Black participants compared with White participants, but associations
between exposures and outcomes were imprecise and inconsistent across models. Secondary
analyses evaluating the role of socioeconomic status suggested partial confounding of the PM₂.₅–
dementia relationship, with attenuation of effect estimates after adjustment for county-level
indicators of education, employment, and housing.
Conclusion: Results provide preliminary evidence that early-life air pollution exposures may
contribute to racial disparities in dementia risk. Findings underscore the need for life course
approaches to dementia prevention and highlight the importance of addressing structural
inequities in early-life environments.