Background/Objectives Long-term exposure to ambient air pollution has been associated with decreased cognitive function, but the effects of traffic pollution on the elderly have not been studied in detail. Accordingly, the objective of this study was to evaluate the association between residential distance to major roadway, as a marker of long-term exposure to traffic pollution, and cognitive function in seniors. Design, Setting, Participants A prospective cohort study of 765 community-dwelling seniors with median follow-up of 16.8 months. Measurements We administered the Mini Mental State Exam (MMSE), Hopkins Verbal Learning Test-Revised (HVLT-R), Trail Making Test (TMT), category and letter fluency tests, and clock-in-the-box test (CIB) during home visits on 2 occasions. We calculated the residential distance to nearest major roadway and used generalized estimating equations to evaluate the association between performance on each test and residential distance to major roadway adjusting for participant demographics, education, socioeconomic status and past medical history. Results Decreasing distance to major roadway was associated with statistically significantly poorer performance on the immediate and delayed recall components of the HVLT-R, TMT part B, TMT delta, and the letter and category fluency tests. Generally, participants residing <100 m from a major roadway performed worst. Performance improved monotonically with increasing distance. Conclusions In this cohort of community-dwelling seniors, residential proximity to major roadways was associated with poorer performance on cognitive tests of verbal learning and memory, psychomotor speed, language and executive functioning. If causal, these results add to the growing evidence that living near major roadways is associated with adverse health outcomes.

Background Short-term elevations in fine particulate matter air pollution (PM2.5) are associated with increased risk of acute cerebrovascular events. Evidence from the peripheral circulation suggests that vascular dysfunction may be a central mechanism. However, the effects of PM2.5 on cerebrovascular function and hemodynamics are unknown. Methods We used transcranial Doppler ultrasound to measure beat-to-beat blood flow velocity in the middle cerebral artery at rest and in response to changes in end-tidal CO2 (cerebral vasoreactivity) and arterial blood pressure (cerebral autoregulation) in 482 participants from the MOBILIZE Boston Study. We used linear mixed effects models with random subject intercepts to evaluate the association between cerebrovascular hemodynamic parameters and mean PM2.5 levels 1 to 28 days earlier adjusting for age, race, medical history, meteorologic covariates, day of week, temporal trends, and season. Results An interquartile range increase (3.0 μg/m3) in mean PM2.5 levels over the previous 28 days was associated with a 8.6% (95% confidence interval [CI]: 3.7%, 13.8%; p<0.001) higher cerebral vascular resistance and a 7.5% (95% CI: 4.2%, 10.6%; p<0.001) lower blood flow velocity at rest. Measures of cerebral vasoreactivity and autoregulation were not associated with PM2.5 levels. Conclusions In this cohort of community-dwelling seniors, exposure to PM2.5 was associated with higher resting cerebrovascular resistance and lower cerebral blood flow velocity. If replicated, these findings suggest that alterations in cerebrovascular hemodynamics may underlie the increased risk of particle-related acute cerebrovascular events.