Traffic-Related Air Pollution and Cognitive Function in a Cohort of Older Men

TLDR

Traffic‑related particles induce oxidative stress and may harm central nervous system function, potentially leading to cognitive impairment. The study aimed to evaluate the association between black carbon, a marker of traffic‑related air pollution, and cognition in older men. Researchers assessed 680 men (mean age 71 ± 7 years) from the Veterans Affairs Normative Aging Study, measured long‑term black carbon exposure with a validated spatiotemporal land‑use regression model, and administered a battery of seven cognitive tests between 1996 and 2007, log‑transforming black carbon values for analysis. Each doubling of black carbon exposure was linked to a 30 % higher odds of a Mini‑Mental State Examination score ≤25 and a 0.054‑standard‑deviation decline in global cognition, with no heterogeneity across tests and comparable findings after adjusting for past lead exposure.

Abstract

Traffic-related particles induce oxidative stress and may exert adverse effects on central nervous system function, which could manifest as cognitive impairment.We assessed the association between black carbon (BC), a marker of traffic-related air pollution, and cognition in older men.A total of 680 men (mean ± SD, 71 ± 7 years of age) from the U.S. Department of Veterans Affairs Normative Aging Study completed a battery of seven cognitive tests at least once between 1996 and 2007. We assessed long-term exposure to traffic-related air pollution using a validated spatiotemporal land-use regression model for BC.The association between BC and cognition was nonlinear, and we log-transformed BC estimates for all analyses [ln(BC)]. In a multivariable-adjusted model, for each doubling in BC on the natural scale, the odds of having a Mini-Mental State Examination (MMSE) score ≤ 25 was 1.3 times higher [95% confidence interval (CI), 1.1 to 1.6]. In a multivariable-adjusted model for global cognitive function, which combined scores from the remaining six tests, a doubling of BC was associated with a 0.054 SD lower test score (95% CI, -0.103 to -0.006), an effect size similar to that observed with a difference in age of 1.9 years in our data. We found no evidence of heterogeneity by cognitive test. In sensitivity analyses adjusting for past lead exposure, the association with MMSE scores was similar (odds ratio = 1.3; 95% CI, 1.1 to 1.7), but the association with global cognition was somewhat attenuated (-0.038 per doubling in BC; 95% CI, -0.089 to 0.012).Ambient traffic-related air pollution was associated with decreased cognitive function in older men.