Casey, Joan AHarkin, Ciara2025-10-022025-10-022025-10-022025Harkin_washington_0250O_28924.pdfhttps://hdl.handle.net/1773/54015Thesis (Master's)--University of Washington, 2025Background: 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 source-specific 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 individual-level 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.application/pdfen-USnoneEpidemiologyEnvironmental scienceEpidemiologyThesis