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Air pollution linked to cognitive decline in elderly


Results from the Nurses’ Health Study suggest air pollution may affect the cognitive skills of older women.

Jennifer Weuve, MPH, ScD, of Rush University Medical Center in Chicago, and colleagues evaluated coarse and fine air pollution 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.

The researchers noted very little has been known about the role of particulate matter exposure in relation to cognitive decline.

“In this large, prospective study of older women, higher levels of long-term exposure to both [coarse and fine particulate matter]were associated with significantly faster cognitive decline,” the researchers wrote in the Feb. 13 issue of the Archives of Internal Medicine.

The researchers commented that these associations were present at levels of particulate matter exposure typical in many areas of the U.S.

“Therefore, if our findings are confirmed in other research, air pollution reduction is a potential means for reducing the future population burden of age-related cognitive decline, and eventually dementia,” the authors wrote.

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Air pollution and ischemic stroke risk

In another study in the same issue, Gregory A. Wellenius, ScD, of Brown University in Providence, R.I., and colleagues evaluated the association between changes in fine particulate matter air pollution levels and the risk of ischemic stroke among patients living in the greater Boston area who were admitted between 1999 and 2008 to Beth Israel Deaconess Medical Center.

The authors reviewed the medical records of 1,705 patients hospitalized with ischemic stroke. During the study period, fine particulate air pollution (PM2.5) levels in the Boston area did not exceed current EPA standards.

Daily changes in levels of ambient fine particulate matter air pollution have been associated with higher risk of acute cardiovascular events, excess hospitalizations and deaths, researchers wrote in the study background.

“We found that ischemic stroke risk was 34% higher on days with moderate PM2.5 levels compared with days with good levels, according to the EPA’s Air Quality Index,” the authors wrote.

They added that stroke risk was more strongly associated with concentrations of black carbon and nitrogen dioxide markers of traffic pollution than with components linked to non-traffic sources.

“Current U.S. and World Health Organization air quality standards focus only on daily and annual PM2.5 mean concentrations,” wrote Robert D. Brook, MD, of the University of Michigan in Ann Arbor, and Sanjay Rajagopalan, MD, of the Ohio State University Medical Center in Columbus, in an accompanying commentary. But “there is no biological basis that these specific durations of exposure are required to instigate strokes or other CV events.”

To read a study summary and access the study via subscription or purchase, visit


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