Video: Traffic may trigger heart attacks

By JoNel Aleccia Health writer
msnbc.com
updated 3/13/2009 4:01:49 PM ET 2009-03-13T20:01:49

The next time you’re trapped in traffic, fuming that your fellow drivers and their fetid vehicles are about to give you a heart attack, here’s another good reason to pull over:

You might be right.

New research from Germany shows that people who had heart attacks were three times more likely than not to have been sitting in traffic an hour before their symptoms began.

The risk was even higher for women, older men, the unemployed and those with a history of agina, or chest pain, according to Annette Peters, the researcher who led the study of some 1,454 heart attack patients.

And while cars were the primary traffic source for the heart attack patients she studied, risk also tripled for people who used public transportation or rode bicycles.

“Driving or riding in heavy traffic poses an additional risk of eliciting a heart attack in persons already at elevated risk,” said Peters, who heads the research unit at the Institute of Epidemiology of Helmholtz Zentrum München, the German Research Center for Environmental Health.

Heart attack warning signsAir pollution? Stress?
Exactly why sitting in traffic appears to trigger heart attacks isn’t clear, either from this study or from a previous similar study. There’s a good chance, however, that air pollution may be a key culprit, with a bit of road rage contributing as well.

“One potential factor could be the exhaust and air pollution coming from other cars,” Peters said. “But we can’t exclude the synergy between stress and air pollution that could tip the balance.”

That echoes a growing body of research aimed at determining outside influences on heart attacks, said Dan Greenbaum, president of the Health Effects Institute in Boston, an independent, nonprofit research group.

“It could be air pollution, it could be stress, it could be noise,” he said.

Doctors have long known that anger and stress contribute to long- and short-term heart problems. Stress narrows arteries, boosts blood pressure and even alters the electrical rhythm of the heart.

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Air pollution has traditionally been linked to respiratory troubles and lung disease. But scientists have found an increasingly strong association between air pollution and the development of heart disease, including problems that lead to early death.

“Additional evidence has accumulated that short-term and long-term exposure to air pollution is associated with coronary heart disease events,” Peters said. “I consider that the link between air pollution and cardiovascular disease is most likely causal.”

Ultrafine particles linked to heart disease
Ultrafine particles contained in the pollution are the problem. Scientists believe that the tiny particles get sucked into the lungs, then passed to the blood and to the heart, Greenbaum said. Or the particulates may cause enough inflammation in the lungs to interfere with electrical signals in the body, disrupting the heart.

“But there is nothing as strong as this direct relationship between traffic and heart attacks,” he said.

Peters’ research confirmed a 2004 study she published in the New England Journal of Medicine. For the latest study, she focused on heart attack victims logged in a German registry between February 1999 and December 2003 who survived at least 24 hours after the incidents. The average age was 60 and about 25 percent of the patients were women.

Peters asked the patients to answer questions about their activities in the four days preceding the heart attacks, including their exposure to traffic. Previous studies showed that strenuous activity such as snow shoveling or painting a ceiling raised the risk of heart attack by five or six times.

In this study, about 8 percent of the heart attacks were attributable to traffic, Peters said. “It’s just one factor, but it’s not a negligible number.”

It’s still not clear why women’s risk of heart attack was five times higher within an hour of being in traffic, Peters said. Future studies will have to seek a higher number of female patients to find out.

Who can avoid traffic?
In the meantime, the  new research raises an obvious question:  What are people worried about suffering traffic-triggered heart attacks supposed to do? Stay home?

Of course not, said Peters and Greenbaum.  First, they note that the study focused only on heart attack patients, not the general public, who may not be as prone to the problem.

“The risk also applies to the general population.  But in a healthy person, the risk of a heart attack for any particular hour is very low,” Peters noted. “Multiplying a low number by three is not really relevant.”

The best defense against traffic-related heart attacks is likely good health, the scientists agree. People prone to heart disease should seek medical advice about their risk factors and find ways to reduce them, Greenbaum said. That might include improving diet and exercise or starting drug therapy, if warranted.

After that, a little common sense might be in order.

“If you know it is a high pollution day, you should probably stay indoors,” Greenbaum said. “Traffic could be an additional stress factor if you already have the symptoms.”

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