WEDNESDAY, March 21 (HealthDay News) -- Firefighters are much more likely to die from heart disease when they are actually fighting fires, new research finds.

"The fact that firefighters do have a physical risk is not something new," said study author Dr. Stefanos N. Kales, an assistant professor of occupational medicine at the Harvard School of Public Health. "This is the strongest evidence to date that specific firefighting acts can trigger cardiac events."

Although firefighters are required to be physically fit, heart disease causes 45 percent of deaths that occur when they are duty, concludes a report by Kales and his colleagues in the New England Journal of Medicine.

An earlier study suggested that the stress of putting out a fire might play a role in cardiac deaths, Kales said, and that suspicion was confirmed by this latest study. In it, the researchers looked at all the deaths of on-duty firefighters between 1994 and 2004 -- leaving out Sept. 11, 2001, when many deaths were due to the collapse of the World Trade Center.

Data from several sources, including 17 metropolitan fire departments, indicated that 32.1 percent of the cardiac deaths were associated with the acts involved in suppressing a fire, the researchers found. The odds of cardiac death were anywhere from 12 to 136 times higher when compared to nonemergency duty.

The report has lessons for firefighters and their doctors, Kales said. "Physicians should be aggressive in treating firefighters' cardiac risk factors," he said. "When counseling them about return to work, they should exercise extreme caution."

And while physical fitness is part of the job, Kales said, an earlier study by his group found that "a quarter of the firefighters who died of heart disease on duty had a prior diagnosis of cardiovascular disease."

It's not easy for a firefighter to pay close attention to cardiac risk factors such as high blood pressure, Kales acknowledged. "It is hard in any population," he said. "Most firefighters are men, and men in general do not like to go to a doctor. And they might be concerned that, in medical screening, something could be found that would not make them eligible for a job they love to do."

The solution is to have concern for cardiac fitness become an integral part of that job, Kales said. "Health and fitness should be part of a firefighter's culture from the beginning, when he becomes a recruit," he said.

The study does not say that firefighters are at an unusual risk of cardiac death, said Dr. Linda Rosenstock, dean of the University of California, Los Angeles, School of Public Health and former head of the U.S. National Institute for Occupational Safety and Health, who wrote an accompanying editorial.

"They are a healthy workforce," Rosenstock said. "The overall risk is about the same as for other work populations."

But fighting a fire is not ordinary work, she said. "We've known for a couple of decades that when you have underlying cardiac disease and are put under stress, you are likely to have a cardiac event," Rosenstock said. "It is a clustering phenomenon. We can learn from this study to try to put into effect the best protection firefighters can have in this situation."

The first protective measure is "the same as for the rest of us, to keep as heart-healthy as can be," she said. "Also we have to protect against certain exposures that are unique to firefighting." Protection is needed against particulates and carbon monoxide, toxic products of combustion, both during and immediately after a fire, Rosenstock said.

"We have made progress over the past 20 years in such things as respiratory protection," she said.

More information

Read more about firefighter fatalities at the National Institute for Occupational Safety and Health.

SOURCES: Stefanos N. Kales, M.D., assistant professor, occupational medicine, Harvard School of Public Health, Boston; Linda Rosenstock, M.D., dean, University of California, Los Angeles, School of Public Health; March 22, 2007,

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