Study finds chances of heart attack triples in first hour afterward
FRIDAY, March 13 (HealthDay News) -- Forget road rage. A new study out of Germany has uncovered evidence that getting stuck in traffic prompts an even more serious and immediate consequence -- a much higher risk for suffering a heart attack.
The finding does not isolate which particular virtue of road congestion -- stress, pollution, car exhaust or noise -- might be the driving force behind the apparent cardiovascular threat.
However, after a four-year analysis of nearly 1,500 heart attack cases, the authors came to the conclusion that making one's way through traffic -- whether as a driver, a rider of public transport, or even a bicyclist -- seems to more than triple the chances for experiencing a heart attack in the first hour immediately following exposure.
"We found that when people are participating in traffic, they have a threefold increased risk to experience a heart a attack one hour later," said study author Annette Peters, head of the research unit at the Institute of Epidemiology in Helmholtz Zentrum Munchen, Germany, and an adjunct associate professor in Harvard's School of Public Health.
"For someone with a very low risk for a heart attack, this doesn't mean much," Peters noted. "But for someone already at a higher risk for a heart attack -- because of lifestyle issues such as smoking or being overweight, or perhaps because of genetic makeup -- then traffic might be an additional stressor that could cause a heart attack to occur at this time."
The finding was expected to be presented Thursday at the American Heart Association's Cardiovascular Disease Epidemiology and Prevention annual conference, in Palm Harbor, Fla.
To explore the issue, the German team focused on a pool of heart patients in the southern German town of Augsburg.
One-quarter of the patients were women, and the average age was 60. All had suffered a heart attack between 1999 and 2003, and all were subsequently interviewed to recall experiences in the four days leading up to the event that might have triggered the first symptoms.
The researchers found that 8 percent of the heart attacks were specifically attributable to having been in traffic -- the kind which Peters described as "local, everyday life commuting."
In addition to identifying a 3.2 times higher risk for suffering a heart attack within the first hour after traffic exposure, the research team found that even six hours after exposure, there remained a significant -- though small -- increase in risk.
Being the driver of a car was the most common form of traffic exposure, followed by being a rider of public transportation and/or bicycling.
Patients who had a prior history of angina -- as well as women, elderly men and the unemployed -- appeared to be particularly sensitive to the observed increase in risk. Women, in fact, were found to have a five times greater risk for a heart attack following such exposure -- a gender bump the researchers suggested might be rooted in physiological differences or simply a reflection of the smaller number of women included in the study.
Going forward, Peters and her associates have embarked on further studies to try to determine exactly what aspects of traffic could account for the connection.
Meanwhile, two experts point out that a number of recent studies have already specifically and strongly tied traffic-related exhaust and air pollution exposure to health problems.
"This data is very consistent with reports that this kind of exposure leads to inflammation, cholesterol build-up in the arteries and heart attacks, although there's also a lot of data about stress and its connections to heart attacks," said Dr. Gregg C. Fonarow, a professor of cardiology at the University of California, Los Angeles. "So, probably both of these factors are working synergistically to raise the cardiovascular risk."
For his part, Dr. Bertram Pitt, a professor of medicine emeritus at the University of Michigan School of Medicine in Ann Arbor, agrees "there's enough basic evidence to suggest that air pollution of this kind increases oxidative stress, and could lead to vascular trauma."
"So I'm not surprised by this finding at all," added Pitt. "It's very plausible and very worthy of further exploration."
"But," noted Fonarow, " I think it's important to keep in perspective that although the relative risk for heart attack was high following traffic exposure, the absolute risk was actually very, very small. Meaning, that given the number of times individuals are exposed to traffic and do not have heart attacks, these findings should not alarm the average person, because in absolute terms, the risk that being exposed to traffic every day will provoke a heart attack is exceptionally low."
For more on heart disease risk and air pollution, visit the American Heart Association.
SOURCES: Annette Peters, head, research unit, Institute of Epidemiology, Helmholtz Zentrum Munchen, Germany, and adjunct associate professor, Harvard School of Public Health, Boston; Gregg C. Fonarow, M.D., professor, cardiology, University of California, Los Angeles; Bertram Pitt, M.D., professor, medicine emeritus, University of Michigan School of Medicine, Ann Arbor; March 12, 2009, presentation, American Heart Association's Cardiovascular Disease Epidemiology and Prevention annual conference, Palm Harbor, Fla.
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