http://www.medpagetoday.com/Cardiology/Strokes/31158


Air Pollution Tied to Stroke, Cognitive Slide

 By Michael Smith, North American Correspondent, MedPage Today
Published: February 13, 2012

Reviewed by Zalman S. Agus, MD; Emeritus Professor 
University of Pennsylvania School of Medicine.








Action Points

Note that one study indicates that higher levels of long-term exposure to
both coarse and fine particulate matter were associated with significantly
faster cognitive decline in women ages 70 to 81.

Note also that in another study, the risk for ischemic stroke was elevated
acutely following short-term exposure to higher levels of ambient fine
particulate matter.


 

Airborne pollution can have serious consequences for the brain and the heart
even at typical levels of exposure, according to the results of two studies
published in the Feb. 13 issue of Archives of Internal Medicine.
 
In one analysis, researchers led by Gregory Wellenius, ScD, of Brown
University in Providence, R.I., found that short-term exposure to fine
particulate matter - even at levels allowed by the EPA - can increase the
risk of ischemic stroke.
 
In the other study, a team led by Jennifer Weuve, ScD, of Rush University
Medical Center in Chicago, and colleagues found that long-term exposure to
particulate matter speeded up cognitive decline in older women.
 
The first report "adds to the already strong evidence linking (particulate
matter) to cardiovascular effects," wrote Rajiv Bhatia, MD, of the San
Francisco Department of Public Health, in an accompanying commentary.
 
And, he added, the cognition study suggests that "we may not fully
understand the breadth of (particulate matter) health burdens."
 
Bhatia concluded that controlling particulate matter is technically
feasible, but needs "increased efforts to assess exposure at the community
level, more stringent and creative regulatory initiatives, and political
support."
 
Wellenius and colleagues studied links between daily variation in fine
particulate matter - particles less than 2.5 micrometers in diameter - and
stroke incidence in the Boston area.
 
They drew data from medical records of 1,705 patients admitted to a single
institution with neurologist-confirmed ischemic stroke between April 1,
1999, and Oct. 31, 2008.
 
Fine matter concentrations were measured at a central monitoring station,
using EPA guidelines that define moderate air quality as between 15 and 40
micrograms per cubic meter of air and good air quality as 15 micrograms or
lower.
 
The study period included only days in which the air quality was good or
moderate; the researchers excluded 11 days in which it exceeded 40
micrograms per cubic meter.
 
They found that the estimated odds ratio of ischemic stroke onset was 1.34
(95% CI 1.13 to 1.58) following a 24-hour period classified as moderate,
compared with a period in which the air quality was good. The risk increase
was significant at P<0.001.
 
They also found that the relationship between higher particulate levels and
increased risk of stroke was linear, strongest within 12 hours of exposure,
and was seen among patients with strokes caused by large-artery
atherosclerosis or small-vessel occlusion but not cardioembolism.
 
The risk was more strongly associated with markers of traffic pollution -
such as black carbon and NO2 - than with particles linked to nontraffic
sources, they reported.
 
Although the findings add to the evidence linking stroke and air pollution,
there are some "unique" aspects, according to Robert Brook, MD, of the
University of Michigan Ann Arbor, and Sanjay Rajagopalan, MD, of the Ohio
State University Medical Center in Columbus.
 
Specifically, they noted in an accompanying commentary, "the extremely rapid
increase in stroke risk is an important novel insight" that suggests that
current regulatory focus on daily and yearly average concentrations may be
missing the boat.
 
For the cognition study, Weuve and colleagues turned to the long-running
Nurses' Health Study, which began in 1976 with more than 121,000
participants.
 
Between 1995 and 2001, participants 70 or older with no history of stroke
were asked to take part in a study of cognition and 19,049 agreed. Cognitive
testing was done by telephone three times, with about two years between
interviews.
 
The researchers tracked changes in cognition, looking for associations
between both fine and coarse particulate matter, defined, respectively, as
smaller than 2.5 micrometers in diameter and between 2.5 and 10 micrometers.
 
Particulate matter was measured using EPA monitoring data, adjusted to
estimate local exposure for each participant.
 
Analysis showed that higher levels of long-term exposure to both grades of
pollution were associated with "significantly faster cognitive decline," the
researchers found. Specifically: 
The two-year decline on a global score was 0.020 units worse for every
increase of 10 micrograms per cubic meter in long-term exposure to coarse
particles.
 Similarly, the two-year decline was 0.018 units worse for every increase of
10 micrograms per cubic meter in long-term fine particle exposure.
 

The differences, Weuve and colleagues reported, were similar to those
between women in the study who were approximately two years apart in age.
 
The associations, they reported, were found at pollution levels typical in
many areas, suggesting that pollution control might be a way to reduce the
"future population burden of age-related cognitive decline, and, eventually,
dementia."
 

The analysis of cognitive decline had support from the the National
Institute of Environmental Health Sciences, the National Cancer, and the
Environmental Protection Agency.

The journal said the Wellenius and colleagues made no financial disclosures.

Comment author Bhatia had no financial disclosures, the journal said.

The analysis of stroke had support from the National Institute of
Environmental Health Sciences and the Environmental Protection Agency.

Some of the authors reported financial support from the Health Effects
Institute in Boston, the Electric Power Research Institute in Palo Alto,
Calif., the Environmental Protection Agency, and the NIH.

Comment authors Brook and Rajagopalan had no financial disclosures, the
journal said.


From the American Heart Association: 
Air Pollution and Cardiovascular Disease



Primary source: Archives of Internal Medicine
 Source reference:
 Weuve J, et al "Exposure to particulate air pollution and cognitive decline
in older women" Arch Intern Med 2012; 172(3): 219-227. 

Additional source: Archives of Internal Medicine
 Source reference:
 Wellenius GA, et al "Ambient air pollution and the risk of acute ischemic
stroke" Arch Intern Med 2012; 172(3): 229-234. 

Additional source: Archives of Internal Medicine
 Source reference:
 Bhatia R "Policy and regulatory action can reduce harms from particulate
pollution" Arch Intern Med 2012; 172(3): 227-228.

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