(Reuters Health) - Most firefighters who die from cardiac arrest turn out to have narrowing of the heart arteries or structural damage in their hearts, a recent study suggests.
When firefighters become suddenly incapacitated on the job, it endangers their lives. It may also put other lives at risk as they work to rescue people from burning buildings or douse flames before they spread, researchers note in the Journal of the American Heart Association.
Despite this obvious risk, research to date hasn’t offered a clear picture of why so many firefighters killed on the job die of cardiac arrest rather than from fire-related injuries.
“Fire service statistics had long indicated that sudden cardiac events were a leading cause of line of duty death among firefighters,” said study leader Denise Smith. Research shows that firefighters are more likely to suffer a cardiac event after fire-fighting versus station duties, added Smith, who directs the First Responder Health and Safety Lab at Skidmore College in Saratoga Springs, New York.
To see why these heart-related deaths occur, researchers examined autopsy data from 627 male firefighters, ages 18 to 65, who died between 1999 and 2014, including 276 cardiac cases and 351 trauma cases.
Surprisingly, less than one in five cardiac cases were heart attack deaths, Smith said by email.
Instead, 82 percent of those who died had evidence of coronary heart disease - narrowing of the heart arteries - or enlarged hearts.
Having an enlarged heart or evidence of a prior heart attack were each tied to a six-fold increase in risk of sudden cardiac death, the study found, while having a coronary artery that was 75 percent narrowed was tied to a nine-fold rise in risk.
While the study can’t prove whether or how working as a firefighter might make heart disease more likely, several aspects of the job could explain the connection, Smith said.
Exposure to smoke, soot and chemicals in the air, as well as disrupted sleep patterns and high levels of occupational stress might all contribute to heart problems, Smith noted.
It’s not clear whether firefighters’ risk of heart disease, is higher or lower than other people in different lines of work. “However, the research clearly shows that the stress of firefighting - the heavy muscular work, heat stress, sympathetic nervous system activation, and exposure to smoke - can trigger a cardiac event in individuals with underlying disease,” Smith said.
One limitation of the study is that the autopsies didn’t have uniform descriptions of heart disease or criteria for defining an enlarged heart, the authors note. Researchers also lacked data on certain risk factors for heart disease like smoking or high blood pressure.
Still, the results offer fresh evidence of the dangers of high-stress, physically demanding jobs for people with underlying heart disease, noted Dr. Stefanos Kales, a researcher at Harvard Medical School and the Harvard TH Chan School of Public Health in Boston who wasn’t involved in the study.
“In essence, for persons who have developed underlying heart disease, it is dangerous to perform heavy work, especially in stressful situations that produce a surge of adrenaline and related hormones that challenge the cardiovascular system through a variety of mechanisms,” Kales said by email.
“Therefore, while firefighter screening has traditionally focused on coronary artery disease (cardiac risk factors and stress tests), it should also include imaging such as an echocardiogram to identify possible heart enlargement, increased wall thickness or the presence of an old heart attack,” Kales said.
SOURCE: bit.ly/2OkfJeI Journal of the American Heart Association, online September 5, 2018.