Few commuters will be surprised to hear that driving in traffic is bad for their health. And a new study illustrates exactly how dangerous the roads can be.
According to a study in today's New England Journal of Medicine, air pollution not only causes long-term health problems, but it might also trigger heart attacks.
Doctors asked nearly 700 patients to describe what they had been doing in the hours before they had a heart attack. The physicians were surprised by their findings: Patients were nearly three times as likely to have been in traffic in the hour before the attack than to have been someplace else.
Automobile drivers weren't the only ones at risk. Bus passengers and those who ride bicycles also were more likely to have heart attacks, the study said. That suggests the culprit probably isn't stress but particles spewed by cars and trucks, says Annette Peters, an author of the study from the GSF-National Research Center for Environment and Health in Neuherberg, Germany.
The risk of a heart attack was greatest within an hour of being in traffic, Peters says, but falls back to about normal after three hours.
Doctors note that the overall risk of having a heart attack after being in traffic is still very low. Many things can trigger heart attacks in people with underlying cardiovascular disease, including strenuous exercise, anger and drug use. Doctors blamed traffic for 8% of attacks in this study.
Peters says the research underscores the need for better urban planning. ''It would help to get cleaner vehicles and to have fewer vehicles on the street,'' Peters says.
Experts say the study adds to a large body of evidence linking traffic, air pollution and heart disease. People who live near major roads are at greater risk of dying from lung and heart problems.
Research also shows that people in cars and buses are exposed to 10 times the pollutants and toxic compounds as people on the sidewalk, largely because of emissions from the tailpipes of cars in front of them.
Doctors have known for years that pollution leads to long-term heart disease, says Peter Stone, director of the clinical trials center at Harvard Medical School and Brig-ham and Women's Hospital, who wrote an accompanying editorial. Air pollution worsens hardening of the arteries, blood clots and inflammation. It also constricts blood vessels and disturbs the heart's natural rhythm.
In the short term, Stone says, particles also increase inflammation, which can cause the rupture of plaques in arteries around the heart. Those ruptures can lead to blood clots that choke off the blood supply and cause a heart attack.
Cardiologist Michael Lauer, a professor of medicine at the Cleveland Clinic Lerner College of Medicine, says the article points to the need to reduce pollution.
''This is a public health menace,'' Lauer says. ''It is the responsibility of the public, and the public's representatives in government, to do something about it.''
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