Cognitive impacts of ambient air pollution in the National Social Health and Aging Project (NSHAP) cohort.

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 (PM) were estimated for each participant using GIS-based spatio-temporal models, and exposures to nitrogen dioxide (NO) were obtained from the nearest EPA monitors.

RESULTS

In adjusted linear regression models, IQR increases in 1 to 7year PM 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 NO were equivalent to aging 1.9years. The impacts of PM on cognition were modified by stroke, anxiety, and stress, and were mediated by depression. The impacts of NO were mediated by stress and effect modification by impaired activities of daily living for NO was found.

CONCLUSIONS

Exposures to long-term PM and NO 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 PM on cognition. Additionally, mediation results suggest that PM may impact cognition through pathways related to mood disorders.