Association of Tailpipe-Related and Nontailpipe-Related Air Pollution Exposure with Cognitive Decline in the Chicago Health and Aging Project

Background: Evidence suggests that long-term exposure to air pollution may increase the risk of dementia and related cognitive outcomes. A major source of air pollution is automotive traffic, which is modifiable by technological and regulatory interventions.

Objectives: We examined associations of four traffic-related air pollutants with rates of cognitive decline in a cohort of older adults.

Methods: We analyzed data from the Chicago Health and Aging Project (CHAP), a longitudinal (1993-2012) community-based cohort study of older adults that included repeated assessments of participants' cognitive performance. Leveraging previously developed air pollution models, we predicted participant-level exposures to the tailpipe pollutants oxides of nitrogen (${\mathrm{NO}}_X$) and nitrogen dioxide (${\mathrm{NO}}_2$), plus the nontailpipe pollutants copper and zinc found in coarse particulate matter [PM with aerodynamic diameter $2.5\mu m$ to $10\mu m$ (${\mathrm{PM}}_{2.5-10,\mathrm{Cu}}$) and ${\mathrm{PM}}_{2.5-10,\mathrm{Zn}}$, respectively], over the 3 y prior to each participant's baseline assessment. Using generalized estimating equations, we estimated covariate-adjusted associations of each pollutant with rates of cognitive decline. We probed the robustness of our results via several sensitivity analyses, including alterations to the length of the exposure assessment window and exploring the influence of pre- and post-baseline selection bias.

Results: Using data from 6,061 participants, estimated associations of these pollutant exposures with cognitive decline were largely inconsistent with large adverse effects. For example, a standard deviation ($5.8\text{ppb}$) increment in ${\mathrm{NO}}_X$ corresponded to a slightly slower rate of cognitive decline [e.g., mean difference in change in global score, 0.010 standard unit/5 y, 95% confidence interval (CI): $\mathrm{-0}\mathrm{.016}$, 0.036]. The results of most of our sensitivity analyses were in generally similar to those of our main analyses, but our prebaseline selection bias results suggest that our analytic results may have been influenced by differential survivorship into our study sample.

Discussion: In this large prospective cohort study, we did not observe compelling evidence that long-term TRAP exposure is associated with cognitive decline. https://doi.org/10.1289/EHP14585.