Chronic exposure to air pollution and cognitive decline in older adults

Abstract

BACKGROUND AND AIM: Growing epidemiologic evidence suggests chronic exposure to fine particulate matter (PM2.5) increases risk of dementia in older adults. Despite this, studies of cognitive impairment, a prodromal sign of dementia, report inconsistent results. Studying repeated measures of cognitive function, rather than measures at a single time point, may be a more robust metric of cognitive outcomes because the study design adjusts for time-fixed confounders that affect air pollution exposure and performance on cognitive tests. Therefore, we examined the effect of air pollution on cognitive decline in a U.S. cohort of older adults. METHODS: This analysis draws from the Ginkgo Evaluation of Memory Study, a clinical trial aimed at understanding dementia prevention. Participants aged 75 years and older were enrolled between 2000 and 2002 and completed a neuropsychological battery of 10 tests repeated annually for up to eight years. Tests examined domains of memory, visuospatial abilities, language, attention, and executive function. Chronic exposure (20 years before baseline) to PM2.5 was estimated using annual averages from fine-scale spatiotemporal models and accounted for residential mobility. Trajectories of cognitive function across levels of PM2.5 were compared using generalized estimating equation regression models to account for correlations among repeated cognitive scores. Models included demographic and socioeconomic characteristics as covariates. RESULTS:This study included 2,587 individuals (mean age=78 years) free of mild cognitive impairment at baseline. Chronic exposure to PM2.5 was associated with lower overall scores of memory and visuospatial abilities. Increased exposure to PM2.5 was not associated with declines in either domain. Associations with language, attention, and executive function will be assessed in future analyses. CONCLUSIONS:This study provides support for associations between increased exposure to particulate matter and worse memory and visuospatial abilities. However, preliminary findings show no association between increased exposure and cognitive decline. KEYWORDS: Air pollution, epidemiology, neurodegenerative outcomes