Long-term
exposure to urban air pollution incrementally increases the risk of high blood
pressure, according to a study released Tuesday of more than 41,000 European
city-dwellers.
Constant
noise pollution — especially traffic — also boosts the likelihood of
hypertension, researchers reported in the European Heart Journal.
High
blood pressure is the most important risk factor for premature illness and
death.
The study
found that one extra adult per 100 people of roughly the same age developed
high blood pressure in the most polluted part of towns compared to more
breathable neighbourhoods.
The risk
is similar to being clinically overweight with a body mass index (BMI) of
25-30, the researchers said.
To carry
out the study, 33 experts led by Barbara Hoffmann, a professor at
Heinrich-Heine-University in Duesseldorf, Germany, monitored 41,071 people in
Norway, Sweden, Denmark, Germany and Spain for five to nine years.
At the
same time, the researchers examined air quality annually in each locale during
three two-week periods between 2008 and 2011, measuring different sizes of
particle matter.
Every
increment of five micrograms — or millionths of a gram — of the smallest of
these particles upped the risk of hypertension by a fifth for people living in
the most polluted areas, compared to those in the least polluted.
None of
the participants had hypertension when they joined the study, but during the
follow-up period 6,207 people — 15 percent — reported that they developed
hypertension or started to take medication to lower blood pressure.
For noise
pollution, the researchers found that people living on busy streets with loud
night-time traffic had, on average, a six percent increased risk of developing
hypertension compared to areas where noise levels were at least 20 percent
lower.
"Our
findings show that long-term exposure to particulate air pollution is
associated with a higher incidence of self-reported hypertension,"
Hoffmann said in a statement.
Even when
noise was excluded, the impact of air pollution on blood pressure remained, she
added.
"Current
legislation does not protect the European population adequately from adverse
effects of air pollution," the researchers concluded.
Pollution
levels were higher in Spain and Germany than in the Nordic countries, Hoffmann
noted.
Air
pollution is thought to affect the heart and blood vessels by causing
inflammation, a build-up of damaging molecules, known as oxidative stress, and
an imbalance in the nervous system.
Noise is
thought to affect the functioning of both the nervous and hormonal systems.
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