Feb. 23, 2011 -- If policy makers want to prevent heart attacks, they should focus on improving air quality, a new study suggests.
The study, which is published in TheLancet, is one of the first to rank the relative contributions of 14 triggers -- including cocaine and alcohol use, anger, and physical exertion -- to heart attacks in the general population.
Fine particles in the air that are generated by traffic and power plants, researchers found, trigger about the same number of heart attacks as experiencing negative emotions, heavy physical exertion like shoveling snow, and heavy alcohol.
The researchers stress that on an individual level the risk that air pollution will trigger a heart attack is relatively low. But when those small risks are applied to a large number of people, the threat becomes more evident.
“The analysis is not very complicated, but nobody has ever done that before,” says Andrea Baccarelli, MD, PhD, an associate professor of environmental epigenetics in the department of environmental health at the Harvard School of Public Health, Boston. “Especially to compare air pollution to other risk factors, which is really brilliant, I think.”
“Air pollution really is a huge problem for communities,” says Baccarelli, who wrote a commentary that accompanied the study. “I think they really positioned themselves well to show that.”
For the study, researchers pooled data from 36 studies of exposures that are thought to play a role in triggering heart attacks. Participants ranged in age from an average of 44 in a study on cocaine to an average of 72 in studies of respiratory infections.
They then calculated the odds that being exposed to that variable would lead to a heart attack.
Being exposed to cocaine, for example, increased the relative risk of a heart attack by nearly 24-fold, while being exposed to particulate air pollution increased the odds of having a heart attack by only about 5%.
Though cocaine is more likely to cause a heart attack than air pollution in any one individual, a much smaller number of people are thought to be exposed to cocaine in the population than are exposed to dirty air, making air pollution’s contribution to the total number of heart attacks, it’s so-called population attributable fraction, or PAF, much greater than cocaine’s.
In a scientific statement on the cardiovascular risks associated with air pollution published last year by the American Heart Association, researchers concluded that every 10 microgram per cubic meter increase in the concentration of small particulates contributed to the premature death of one susceptible person the following day in a population of 5 million people.
“Although the dangers to 1 individual at any single time point may be small,” the study’s researchers wrote, “the public health burden derived from this ubiquitous risk is enormous.”
The researchers of The Lancet study agree.
“The relevance of air pollution as a trigger in the populations is of the same magnitude of risk than many other clinically appreciated or recognized triggers for MI [myocardial infarction],” study researcher Tim S. Nawrot, PhD, Centre for Environmental Sciences HasseltUniversity Diepenbeek, Belgium tells WebMD.
“Our work stands as a warning against overlooking the public health relevance of ubiquitous risk factors with moderate or weak strength that have high frequency in the community.”