Air Pollution May Up Fatal Stroke Risk
Risk May Be Tied to Fine Particle Pollution During Warm Months, Study Shows
WebMD News Archive
Feb. 15, 2007 -- Fine particles in air pollution may raise fatal stroke risk
in people aged 65 and older during warm months.
So say experts including Jaana Kettunen, MSc, of Finland's National Public
Kettunen's team studied fatal stroke risk and air pollution among people 65
and older in Helsinki, Finland's capital.
The study, published in Stroke, shows a rise in fatal stroke risk
among people 65 and older on warm days when the air was laden with fine
Based on the findings, Kettunen offers some advice in an American Stroke
Association news release.
"We suggest that on high pollution days, elderly people should avoid
spending unnecessary time in traffic, whether in a vehicle or walking,
especially if they suffer from cardiovascular diseases, to lower their exposure
to pollutants," says Kettunen.
"They should also avoid heavy outdoor exercise on high pollution days,
and nursing homes, for example, should not be built along heavily trafficked
roads, where particle concentrations are at their highest."
Kettunen and colleagues studied air pollution and fatal stroke in
metropolitan Helsinki -- where about a million people live -- from 1998 to
During those years, 3,265 people 65 and older died of stroke in metropolitan
Helsinki, the study shows.
Most of the deaths -- 1,961 -- occurred during the cold months of October to
April. The other 1,304 deaths happened during Helsinki's warm season, May to
The researchers also checked Helsinki's outdoor air pollution levels during
the months. Data came from pollution-measuring stations around Helsinki.
Kettunen's team paid special attention to fine particles. Fine particles
mainly come from combustion engines and have been suggested to be
"especially harmful," write the researchers.
Pollution and Fatal Stroke Risk
Although stroke deaths were most common during the cold season, the mix of
warm weather and pollution may have upped fatal stroke risk.
When outdoor levels of fine particle pollution were high, fatal stroke risk
rose -- but only during Helsinki's warm season.
High levels of fine particle pollution weren't linked to fatal stroke risk
during Helsinki's cold months. Though fine particle pollution was actually a
bit higher during the cold months, the study shows.
But the researchers note that people spend more time outdoors, and are thus
exposed to more air pollution, during warm weather.
During Finland's frigid months, people tend to nestle indoors. That cuts their
exposure to air pollution, possibly lowering their risk of suffering a fatal
Ultrafine particle pollution, carbon monoxide, and coarse particle pollution
weren't strongly linked to fatal stroke risk.
The study doesn't prove that pollution causes stroke.
Many factors -- including age, heart disease, smoking, and diabetes -- may
make people more vulnerable to stroke. Kettunen's study didn't track those risk
factors among the people who died of stroke.
The study only included fatal strokes. Future studies should also look at
nonfatal stroke risk, the researchers suggest.