Residential proximity to nearest major roadway and cognitive function in community-dwelling seniors: results from the MOBILIZE Boston Study.

OBJECTIVES: To evaluate the association between residential distance to nearest major roadway, as a marker of long-term exposure to traffic pollution, and cognitive function in older adults.
DESIGN: Prospective cohort study with median follow-up of 16.8 months.
SETTING: Community. PARTICIPANTS: Seven hundred sixty-five community-dwelling seniors. MEASUREMENTS: The Mini-Mental State Examination, Hopkins Verbal Learning Test-Revised (HVLT-R), Trail Making Test (TMT), category and letter fluency tests, and Clock-in-the-Box Test were administered during home visits on two occasions. The residential distance to the nearest major roadway was calculated, and generalized estimating equations were used to evaluate the association between performance on each test and residential distance to nearest major roadway, adjusting for participant demographics, education, socioeconomic status, and past medical history.
RESULTS: Shorter 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 letter and category fluency tests. Generally, participants residing less than 100 m from a major roadway performed worst. Performance improved monotonically with increasing distance.
CONCLUSION: In this cohort of community-dwelling older adults, residential proximity to a major roadway 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.