Urban but not rural patterns of ambient air pollution exposure is associated with an accelerated rate of late life memory decline in the Wisconsin Longitudinal Study

Abstract

AbstractBackgroundExposure to ambient air pollution is an emerging risk factor for dementia, yet air pollution levels are found to vary by neighborhood affluence and across rural/urban settings. In this study, we leverage data from the Wisconsin Longitudinal Study (WLS) to evaluate the effects of ambient air pollution exposure on the rate of memory decline in late life, while accounting for both local (neighborhood) and regional (urbanization) residency characteristics.MethodAnnualized rate of change for both immediate and delayed recall trials of a 10‐item word list were calculated between 2010‐1 (baseline) and 2021‐2 (follow‐up) data collection waves. Yearly averages of geocoded regional air pollution data were obtained for 5 pollutants at baseline: particulate matter > 2.5um (PM2.5), ozone (O3), sulfur dioxide (SO2), nitrogen dioxide (NO2), and carbon monoxide (CO). Principal component analysis was performed to reduce multicollinearity among the 5 pollutants in subsequent analyses. Annualized rate of change in memory measures were regressed on resultant pollutant factor scores, additionally controlling for baseline age, adolescent IQ, education, health conditions (heart disease, stroke, hypertension, diabetes), neighborhood‐level deprivation, ApolipoproteinE‐4 (ApoE‐4) status, and sex.Result3,601 WLS participants were included in analyses, with a mean age of 70.4±3.4 years at baseline and 80.1±3.4 years at follow‐up. PCA yielded a 2‐factor solution classifying air pollutants into distinct urban (PM2.5, NO2, and CO2) versus rural (SO2 and O3) composites. Linear regression analysis revealed that greater annualized decline in delayed recall was predicted by higher exposure to urban air pollutants (but not rural), adolescent IQ, older age at baseline, and a history of heart disease. Air pollution exposure did not predict annualized change in immediate recall.ConclusionUsing longitudinal data from the WLS cohort, we find that higher levels of urban ambient air pollutant exposure predicted a more precipitous decline in delayed memory across late life. This finding remained significant after controlling for relevant confounders including neighborhood disadvantage, adolescent IQ, and ApoE‐4 status. Although the effect size of pollution exposure on the rate of memory decline was small, it remains a modifiable risk factor and stands to inform public policies to optimize late life cognition.