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Heart disease kills more on-duty firefighters than anything else -- and they are definitely linked to emergency duties, a Harvard study shows.

Most people think firefighters' biggest death threats are fires and collapsing buildings. But over the last 30 years it's been shown that 45 percent of firefighters' on-duty deaths come from heart disease.

Firefighters, however, don't have a higher rate of heart deaths than do people in other jobs. So are these deaths really related to the heroic service firefighters provide?

Yes, find Harvard researcher Stefanos N. Kales, MD, MPH, and colleagues. Kales' team analyzed data on all firefighter deaths between 1994 and 2004, except those linked to the 9/11 terrorist attacks. They also looked at how a representative sample of firefighters spend their time.

"What our study is showing is the majority of on-duty heart deaths in firefighters are work related and are precipitated by physical and toxic factors," Kales tells WebMD.

The researchers found that, compared with when they perform nonemergency duties:

? Firefighters are 12 to 136 times more likely to die of heart disease when putting out a fire.

? Firefighters are 3 to 14 times more likely to die of heart disease while responding to an alarm.

? Firefighters are 2 to 10.5 times more likely to die of heart disease while returning from an alarm.

? Firefighters are 3 to 7 times more likely to die of heart disease during physical training.

The findings appear in the March 22 issue of The New England Journal of Medicine.

Firefighters' Hearts

Firefighters are like other people in one respect: Many of them have underlying heart disease. And, like so many other Americans, many firefighters have high cholesterol levels, high blood pressure, and other risk factors that put them at risk of heart disease.

Battling fires and rescuing civilians involves sudden, extreme exertion and exposure to toxic environments. These job risks make heart disease all the more deadly for firefighters.

"Now we provide the strongest evidence to date that specific firefighter duties -- fire suppression, alarm response, and physical training -- can trigger events in firefighters with underlying disease," Kales says.

It's not that firefighters are having heart attacks right and left. Firefighters suffer fewer than 50 on-duty heart deaths a year, notes Linda Rosenstock, MD, MPH, dean of the University of California, Los Angeles School of Public Health.

"We want to avoid every one of those deaths, in this work force particularly, because they put themselves at risk helping us," Rosenstock tells WebMD.

Saving Firefighters' Lives -- and Your Life

Understanding when firefighters are at greatest risk of heart death is the first step toward saving these lifesavers' lives.

"There is a clustering of these events around times of peak physical activity," Rosenstock notes. "They work in tough environments, they wear heavy equipment, they are highly stressed, and they are exposed to chemical toxins that may aggravate their cardiac risk. And all of these exposures are occurring during the period when these fatal events occur."

For all these reasons, underlying heart disease adds a huge risk to an already risky job. That's why Rosenstock recommends that all fire departments should:

? require firefighters to undergo prehire and annual medical examinations

? implement wellness and fitness programs to reduce heart disease risk factors

? require annual physical performance tests for all firefighters

Firefighters tend to be far fitter and healthier than civilians -- especially if they work full time at the job. But 70% of firefighters are volunteers.

"The fitness requirements at entry and continuing through working life are much higher on the career side than on the voluntary side," Rosenstock says. "Very few paid firefighters continue after age 50. But the volunteer work force is older -- and with age comes added risk."

This means that the biggest threat to firefighters may be the fire on the firehouse stove, says nutritionist David W. Grotto, RD, LDN. Grotto's book, 101 Foods That Could Save Your Life, is scheduled for release next year.

Grotto, a spokesman for the American Dietetic Association, remembers going to a Chicago firehouse last summer to teach a seminar on heart-healthy foods.

"The first day I went there, I smelled something like bacon cooking. It was a big pot of sausages and onions all swimming in butter," Grotto tells WebMD. "And as the firefighters gathered around for the seminar, another guy was making them grilled cheese sandwiches on white bread, slathered with margarine."

By the end of the summer, after getting the firefighters to cut back on fats and to eat more soluble fiber and more fruits and vegetable, the firefighters' cholesterol levels sank along with their heart risk.

Grotto didn't teach an exercise class. But he might have. He noticed that the couch in front of the station's huge television set got far more use than the station's weight room.

That lesson isn't just for firefighters. Anyone who leads a largely sedentary lifestyle is at serious risk of heart death with sudden, strenuous exercise.

"This study is a confirmation of what we know: that regular exercise is, in general, protective against heart disease," Kales says. "But if you are sedentary and suddenly embark on physical activity, there is definitely a risk there."

Proper diet and exercise lessens the risk of heart disease. But firefighters who already have heart disease may need to switch to less hazardous duty.

"If significant heart disease is diagnosed in a firefighter, given the dramatic risks involved in these duties, a very careful discussion has to go on in advising this person whether it is safe to return to duty," Kales says. "It is not the same as returning to a desk job after having a heart attack."