Tuesday, February 14, 2012

Soot pollution linked to cognitive impairment in older women

from the Archives of Internal Medicine


Exposure to Particulate Air Pollution and Cognitive Decline in Older Women
Jennifer Weuve, MPH, ScD; Robin C. Puett, MPH, PhD; Joel Schwartz, PhD; Jeff D. Yanosky, MS, ScD; Francine Laden, MS, ScD; Francine Grodstein, ScD

Arch Intern Med. 2012;172(3):219-227. doi:10.1001/archinternmed.2011.683

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 [PM2.5-10]) and fine (PM <2.5 µm in diameter [PM2.5]), 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 PM2.5-10, and PM2.5 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 PM2.5-10 and PM2.5 exposures. The main outcome measure was cognition, via validated telephone assessments, administered 3 times at approximately 2-year intervals, includ-ing tests of general cognition, verbal memory, category fluency, working memory, and attention.

Results Higher levels of long-term exposure to both PM2.5-10 and PM2.5 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/m3 increment in PM2.5-10 exposure and 0.018 (95% CI, –0.035 to –0.002) units worse per 10 μg/m3 increment in PM2.5 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/m3 increment in long-term PM exposure is cognitively equivalent to aging by approximately 2 years.

Conclusion Long-term exposure to PM2.5-10 and PM2.5 at levels typically experienced by many individuals in the United States is associated with significantly worse cognitive decline in older women.

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