Fine Particulate Matter and Dementia in the Adult Changes in Thought Study

Abstract

Background: Air pollution may be associated with elevated dementia risk, but prior research has limitations that may affect reliability, and no prior studies have evaluated this question in a community-based cohort of men and women in the United States. Methods: We evaluated the association of long-term fine particulate matter (PM2.5) exposure with all-cause dementia during the period 1978-2018 in the Adult Changes in Thought (ACT) study based in Seattle, Washington, USA. PM2.5 exposures linked to participant addresses were obtained from a spatiotemporal model spanning 40 years. Research quality dementia diagnoses were made using standardized diagnosis protocols at biennial follow-ups. We conducted multivariate Cox proportional hazards regression to evaluate the association between time-varying, 10-year average PM2.5 exposure and time to event in a model based on age, stratified by apolipoprotein E (APOE) genotype, and adjusted for sex, education, race, neighborhood median household income, and calendar time. Findings: Mean (standard deviation) 10-year average PM2.5 was 10.0 (2.9) µg/m3, which is below the current national air quality standard. Each 1 µg/m3 increase in the moving average of 10-year PM2.5 was associated with a 16% greater hazard of all-cause dementia (1.16 (1.03, 1.31). Interpretation: In this community-based prospective cohort study with uniquely extensive exposure data and research quality outcome ascertainment, elevated long-term exposure to PM2.5 was associated with an increased hazard of all-cause dementia. These results add to growing evidence on the neurodegenerative effects of air pollution and suggest that reducing exposures across the population could contribute to reducing the burden of dementia. Funding: NIEHS F31ES030972-02, NIEHS T32ES015459, NIA T32AG052354, NIEHS and NIA R01ES026187, U01 AG006781, NIEHS ES026187, NIA AG05136, R01 AG056711 and U01 NS091272, the University of Washington Retirement Association Aging Fellowship, and the Seattle Chapter of the Achievement Rewards for College Scientists (ARCS) Foundation. Declaration of Interests: The authors have no conflicts of interest to disclose. Ethics Approval Statement: ACT participants signed forms indicating their informed consent to enroll in the study. Study procedures were approved by the University of Washington and Kaiser Permanente Institutional Review Boards.