from: https://abcnews.go.com/Health/noisy-traffic-linked-heart-attack-risk/story?id=16613762#.T-Zcu1KRMtV

Study Links Traffic Noise and Heart Attack Risk

    By CARRIE GANN
    ABC NEWS MEDICAL UNIT

June 20, 2012

Ah, traffic. Whether you're sitting in it, walking near it or breathing in
fumes from it, traffic seems to be bad for our health in a lot of ways. Today,
researchers in Denmark are reporting on another link between gridlock and
health -- traffic noise may raise the risk of a heart attack.

The researchers found that people who lived with higher levels of traffic
noise around their homes had a higher risk. For every 10-decibel increase
of noise, the risk of a first heart attack went up by 12 percent.

Although previous studies have found some association between traffic
noise and heart health, Dr. Mette Sorensen, the study's lead author, said
she was surprised that this study showed such a specific relationship
between noise levels and increased heart attack risk.

"Previously, there seemed to be no effect up to around 60 decibels," she
said. "But I see increases at around 40 decibels up to the highest level,
around 82 decibels. It doesn't seem to be a level where there are no effects."

The scientists studied more than 50,000 50- to 64-year-olds in two of
Denmark's largest cities, Copenhagen and Aarhus, keeping track of many
aspects of their health, including everywhere they lived for a 10-year
period. Based on the locations of their homes and an analysis of traffic
patterns, Sorensen and her team calculated how much noise each person had
been exposed to. Of the people in the study, 1,600 had their first heart
attack during the decade of the research.

The study was published today in the journal PLoS One.

Cardiologists say the link between traffic noise levels and heart
health is interesting. But the findings don't spell out the exact
reasons for that link.

But they have several guesses for what may be going on. One is a
well-known culprit in increased heart attack risk: stress, which likely
affects many people who live in bustling, noisy cities.

"The noise itself probably does increase stress and the levels of stress
hormones like adrenaline. Your blood pressure is probably going up as
well," said Dr. Robert Bonow, a professor of medicine at the Northwestern
Feinberg School of Medicine.

Past studies of traffic and heart health (*1) have also suggested stress
as a mediator between gridlock and increased health risks.

Dr. Chip Lavie, medical director of cardiac rehabilitation and prevention
at the Ochsner Medical Center in New Orleans, said scientists have found
associations between heart health and psychological stress of all kinds.

Earthquakes, traumatic events like Hurricane Katrina, "even sporting
events have the common theme of increased psychological stress, which
one could theorize is also in play during heavy traffic, with or
without traffic noise," Lavie said.

Sorensen and her colleagues speculated that all the noise might
prevent people from getting adequate sleep, another known risk factor
for heart attacks.

Where there are high volumes of noisy traffic, air pollution is likely
to follow, and cardiologists said that might also have contributed to
the higher heart attack risk for the people in the study because
particles in polluted air are damaging to the heart and blood vessels.
The link between heart health and air pollution is also well-studied:
Most recently, researchers noticed that risk factors for heart disease
decreased in Beijing during the 2008 Olympics (*2), when traffic and
air pollution were kept to lower-than-normal levels.

Sorensen and her team also studied how much air pollution the study
participants experienced, but Sorensen said those results will be
published in a separate study later on.

The people who had heart attacks in the study were at greater risk
from other factors as well: They smoked more, were less physically
active and had poorer diets. Although the researchers tried to rule
out those factors in their statistical analysis, it's often difficult
for researchers to rule out absolutely every variable that might
affect an association between two factors, even when using the best
statistical methods. Dr. David Frid, a cardiologist at the Cleveland
Clinic, said it's hard to discount how other cardiovascular risk
factors may have affected the study participants who had heart attacks.

"Cardiovascular disease is a complex process and there are multiple
factors that could lead to a heart attack," Frid said. "As we identify
these various factors, we have to then be cognizant of what we can do
to ultimately reduce our risk of developing heart disease."

It may not always be possible for people to escape the noisy environment
they live in, so those who hear lots of horns honking and brakes
squealing night and day may need to step up their efforts to get
regular exercise and eat a healthy diet to compensate for that risk.

"Ultimately, if you're living in a place with a lot of noise, it
could potentially put you at higher risk, but we don't know whether
reducing that noise reduces your risk," Frid said.

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*1. Alan Mozes and Healthday Reporter, Traffic jams harm the heart (14 March 2012)
      https://abcnews.go.com/Health/Healthday/story?id=7079435&page=1

*2. ABC News via Good Morning America, Beijing Olympics show air
    pollution-heart attack link (15 May 2012),
      https://abcnews.go.com/blogs/health/2012/05/15/beijing-olympics-shows-pollution-heart-ills-link/