Background: Pathways through which air pollution may impact cognitive function are poorly understood, particularly with regard to whether and how air pollution interacts with social and emotional factors to influence cognitive health.
Objective: To examine the association between air pollutant exposures and cognitive outcomes among older adults participating in the National Social Life, Health, and Aging Project (NSHAP) cohort study.
Methods: Measures of cognitive function, social connectedness, and physical and mental health were obtained for each NSHAP participant starting with Wave 1 of the study in 2005. Cognitive function was assessed using the Chicago Cognitive Function Measure (CCFM) for 3377 participants. Exposures to fine particles (PM2.5) were estimated for each participant using GIS-based spatio-temporal models, and exposures to nitrogen dioxide (NO2) were obtained from the nearest EPA monitors.
Results: In adjusted linear regression models, IQR increases in 1 to 7year PM2.5 exposures were associated with a 0.22 (95% CI: -0.44, -0.01) to a 0.25 (95% CI: -0.43, -0.06) point decrease in CCFM scores, equivalent to aging 1.6years, while exposures to NO2 were equivalent to aging 1.9years. The impacts of PM2.5 on cognition were modified by stroke, anxiety, and stress, and were mediated by depression. The impacts of NO2 were mediated by stress and effect modification by impaired activities of daily living for NO2 was found.
Conclusions: Exposures to long-term PM2.5 and NO2 were associated with decreased cognitive function in our cohort of older Americans, and individuals who experienced a stroke or elevated anxiety were more susceptible to the effects of PM2.5 on cognition. Additionally, mediation results suggest that PM2.5 may impact cognition through pathways related to mood disorders.
Keywords: Air pollution; Cognitive function; Epidemiology; Mental health; Older adults.
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