a large, 1 study led by a researcher at rush university medical center indicates that 2 exposure to 3（微粒的） air pollution may accelerate 4 decline in older adults. the results of the study will be published in the feb. 13 issue of archives of internal medicine, one of the jama/archives journals. in the study, women who were exposed to higher levels of ambient（周围的） particulate matter (pm) over the long term experienced more decline in their cognitive functioning over a four-year period. higher levels of long-term exposure to both coarse pm (pm2.5-10) and fine pm (pm2.5) were associated with significantly faster cognitive decline.
pm air pollution consists of small particles suspended in the air. particles that are less than 2.5 microns in diameter, which is 1/30th the width of human hair, are called fine pm and particles larger than 2.5-10 microns is called coarse（粗糙的） pm.
these associations were present at levels of pm exposure typical in many areas of the united states.
there are few recent studies that 5 air pollution and cognitive function in older adults, but this is the first study to examine change in cognitive function over a period of time and whether exposure to the size of particulate matter is important.
jennifer weuve, mph., scd, assistant professor of the rush institute of healthy aging and the principal 6 of the study, along with her colleagues, evaluated air pollution, both coarse and fine, in relation to cognitive decline in older women using a study population from the nurses' health study cognitive cohort, which included 19,409 u.s. women ages 70 to 81 for a 14-year period going back as far as 1988.
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