Exposure to particulate air pollution and cognitive decline in older women

Background: Chronic exposure to particulate air pollution may accelerate cognitive decline in older adults, although data on this association are limited. Our objective was to examine long-term exposure to particulate matter (PM) air pollution, both coarse ([PM 2.5-10 μm in diameter [PM _2.5-10]) and fine (PM <2.5 μm in diameter [PM _2.5]), in relation to cognitive decline. Methods: The study population comprised the Nurses'Health Study Cognitive Cohort, which included 19 409 US women aged 70 to 81 years. We used geographic information system-based spatiotemporal smoothing models to estimate recent (1 month) and long-term (7-14 years) exposures to PM _2.5-10, and PM _2.5 preceding baseline cognitive testing (1995-2001) of participants residing in the contiguous United States. We used generalized estimating equation regression to estimate differences in the rate of cognitive decline across levels of PM _2.5-10and PM _2.5 exposures. The main outcome measure was cognition, via validated telephone assessments, administered 3 times at approximately 2-year intervals, including tests of general cognition, verbal memory, category fluency, working memory, and attention. Results: Higher levels of long-term exposure to both PM _2.5-10 and PM _2.5 were associated with significantly faster cognitive decline. Two-year decline on a global score was 0.020 (95% CI, -0.032 to -0.008) standard units worse per 10 μg/m ³ increment in PM _2.5-10 exposure and 0.018 (95% CI, -0.035 to -0.002) units worse per 10 μg/m ³ increment in PM _2.5 exposure. These differences in cognitive trajectory were similar to those between women in our cohort who were approximately 2 years apart in age, indicating that the effect of a 10-μg/m ³ increment in long-term PM exposure is cognitively equivalent to aging by approximately 2 years. Conclusion: Long-term exposure to PM _2.5-10 and PM _2.5at levels typically experienced by many individuals in the United States is associated with significantly worse cognitive decline in older women.