Association between Fine Particulate Matter Exposure and Cerebrospinal Fluid Biomarkers of Alzheimer’s Disease among a Cognitively Healthy Population-based Cohort

Abstract

Background: Epidemiological evidence suggests air pollution adversely affects cognition and increases the risk of Alzheimer′s disease (AD), but little is known about the biological effects of fine particulate matter (PM2.5) on early predictors of future disease risk. Objectives: We investigated the association between 1, 3, and 5-year exposure to ambient and traffic-related PM2.5and cerebrospinal fluid (CSF) biomarkers of AD. Methods: We conducted a cross-sectional analysis using data from 1,113 cognitively healthy adults (aged 45-75 years) from the Emory Healthy Brain Study in Georgia, USA. CSF biomarker concentrations of Aβ42, tTau, and pTau, were collected at enrollment (between 2016-2020) and analyzed with the Roche Elecsys system. Annual ambient and traffic-related residential PM2.5concentrations were estimated at a 1km and 250m resolution, respectively, and 3- and 5-year average exposures were computed for each participant based on time of specimen collection. Associations between PM2.5and CSF biomarker concentrations, considering continuous and dichotomous (dichotomized at clinical cut-offs for AD-biomarker positivity) outcomes, were estimated with multiple linear/logistic regression, respectively, controlling for potential confounders (age, gender, race/ethnicity, body mass index, and neighborhood socioeconomic status). Results: Interquartile range (IQR; IQR=0.845) increases in 1-year [β: -0.101; 95%-confidence interval (CI): -0.18, -0.02] and 3-year (β: -0.078; 95%-CI: -0.15, -0.00) ambient fine PM2.5exposures were negatively associated with Aβ42CSF concentrations. Associations between ambient PM2.5and Aβ42were similar for 5-year estimates, but not significant (β: -0.076; 95%-CI: -0.160, 0.005). Dichotomized CSF variables revealed similar and significant associations between ambient PM2.5and Aβ42. Associations with traffic-related PM2.5were similar but not significant. PM2.5exposures were not associated with tTau, pTau, tTau/Aβ42, or pTau/Aβ42levels at enrollment. Conclusion: In our cross-sectional study, PM2.5exposure was associated with a significant decrease in CSF Aβ42which suggests an accumulation of amyloid plaques in the brain and an increased risk of developing AD.