Ambient fine particulate matter exposure and incident mild cognitive impairment and dementia.

Background/objective: Poor air quality is implicated as a risk factor for cognitive impairment and dementia. Few studies have examined these associations longitudinally in well-characterized population-based cohorts with standardized annual assessment of both mild cognitive impairment (MCI) and dementia. We investigated the association between estimated ambient fine particulate matter (PM _2.5 ) and risk of incident MCI and dementia in a post-industrial region known for historically poor air quality.
Setting/participants: Adults aged 65+ years in a population-based cohort (n = 1572).
Measurements: Census tract level PM _2.5 from Environmental Protection Agency (EPA) air quality monitors; Clinical Dementia Rating (CDR)®.
Design: We estimated ambient PM _2.5 exposure (μg/m ³ , single-year and 5-year averages) by geocoding participants' residential addresses to census tracts with daily EPA PM _2.5 measurements from 2002 to 2014. Using Bayesian spatial regression modeling adjusted for age, sex, education, smoking history, and household income, we examined the association between estimated PM _2.5 exposure and risk of incident MCI (CDR = 0.5) and incident dementia (CDR ≥ 1.0).
Results: Modeling estimated single-year exposure, each 1 μg/m ³ higher ambient PM _2.5 was associated with 67% higher adjusted risk of incident dementia (hazard ratio [HR] = 1.669, 95% credible interval [CI]: 1.298, 2.136) and 75% higher adjusted risk of incident MCI (HR = 1.746, 95% CI: 1.518, 2.032). Estimates were higher when modeling 5-year ambient PM _2.5 exposure for incident dementia (HR = 2.082, 95% CI: 1.528, 3.015) and incident MCI (HR = 3.419, 95% CI: 2.806, 4.164).
Conclusions: Higher estimated ambient PM _2.5 was associated with higher risk of incident MCI and dementia, particularly when considering longer-term exposure, and independent of demographic characteristics and smoking history. Targeting poor air quality may be a reasonable population-wide intervention to reduce the risk of cognitive impairment in older adults, particularly in regions exceeding current recommendations for safe exposure to PM _2.5 .
(© 2021 The American Geriatrics Society.)