Firefighters and CVD: Heroes with Hearts at Risk

Background
There are more than one million firefighters in the United States. Excluding the tragic loss of 342 firefighters in New York City on Sept. 11, 2001, approximately 100 firefighters die in the line of duty (LOD) each year in the United States.¹ However, direct fire injury is not – as might be expected - the leading cause of such deaths. In fact, cardiovascular disease (CVD) is the most common cause of LOD deaths among firefighters, accounting for approximately one-half of all firefighter deaths annually.¹ Firefighters experience the highest proportionate LOD mortality because of CVD as compared with other occupational groups, including police and other public safety officers.²

Characteristics of Firefighter CVD Deaths
Approximately 25% of firefighters are employed as full-time career professionals and 75% are volunteers. LOD deaths among firefighters occur in a similar distribution.³ Approximately onethird of all fatal cardiovascular-related events occur during direct fire suppression activity, another one-third en route to or from a fire event, and one-third during other training activities.^3,4 Of particular note, only 1% to 2% of a firefighter’s actual time on duty is devoted to fire events. Accordingly, it has been estimated that the relative risk of a cardiovascular event occurring with fire suppression is from 10- to 100-fold greater than the risk during non-fire suppression activities.⁴ The majority of these deaths occur between noon and midnight, corresponding to the most likely time of fire occurrence, unlike the typical early morning circadian pattern of most cardiovascular events.³ Additionally, for every death, it is estimated that 17 nonfatal cardiac events occur.⁵ Autopsies have tended to show underlying coronary artery disease and/or left ventricular hypertrophy.⁶

Contributing Factors
Multiple factors have been identified that may contribute to the cardiovascular disease risk of firefighters. Traditional risk factors do correlate with firefighter CVD deaths: age > 45 years, current smoking, hypertension, diabetes and prior diagnosis of CHD or other arterial-occlusive disease.³ There is evidence that traditional risk factors – such as obesity, hypertension, dyslipidemia and diabetes – are more common among firefighters than among the general population.⁴ However, smoking appears to be an exception. Firefighters tend to smoke cigarettes less than their comparable male counterparts, although their use of smokeless tobacco may be high.⁷ Superko, et al., observed the presence of coronary artery calcium (CAC) in 35.6% (101/286) of asymptomatic firefighters over the age of 40 in a study of male firefighters without a known history of CVD.⁸ No age-matched controls were reported. In this study, the presence of positive coronary artery calcium was associated with markers of metabolic syndrome - elevated fasting glucose, blood pressure and weight, as well as dyslipidemia. There are additional factors unique to firefighters that may increase the likelihood of an acute cardiovascular event, as listed in Table 1.⁴ Potential mechanisms of action are summarized in Table 2.⁶

Are Firefighters at Greater Risk Than the General Population?
Based on a study of CVD deaths among firefighters in Toronto, Bates estimated that firefighters have an increased risk of fatal CVD from 1.7 to 2.4 times that of the general population.⁹ However, there are no prospective studies comparing firefighters with matched controls. Little data are available on the lifetime risk of firefighters. In their review, Soteriades, et al., suggest that the lifetime risk of CVD for firefighters is about 35%, comparable to the general population.² One potential confounding factor may be the "healthy worker effect." Firefighters are likely to be healthier than the general population at the time of hiring, because those with known CVD are likely to be excluded. Therefore, it is possible that firefighters’ overall risk of cardiovascular disease and death is no greater than the general population, except during very stressful but infrequent work conditions (ie, actual fire events), and only for certain predisposed firefighters. Further study is needed.

Consequences of a Firefighter Cardiovascular Event
There are serious consequences to a firefighter illness or death. Anecdotally, it often is observed that whenever a firefighter "goes down," for whatever reason, the attention of his/her fellow firefighters is diverted to their fallen comrade, rather than the fire they are trying to extinguish. This further contributes to the increased risk of life and property. In the event of death or prolonged disability, the department suffers a significant loss of personnel until that firefighter returns or can be replaced. There are additional economic consequences. The diagnosis of CVD in a firefighter generally is considered work-related, regardless of the circumstances. The 2003 Hometown Heroes Act provides compensation to survivors of firefighters and other emergency personnel who die from CVD.¹⁰

What Is Being Done?
The National Volunteer Fire Council (NVFC) has made awareness of firefighters and CVD a major priority, offering online education, publications and on-site screenings.¹¹ The National Fire Protection Association (NFPA) and Occupational Health and Safety Administration (OSHA) currently recommend, but do not require, thorough annual medical evaluations of firefighters, as well as departmental programs to promote health and fitness.^12,13 Primarily due to financial limitations, many departments offer limited, if any, medical evaluations and fitness programs to their firefighters. Kales, et al., observed that only 25% of the time had firefighters who died from an acute cardiovascular event undergone a medical evaluation in the preceding 24 months.³ To date, there are no known studies reporting a proven strategy to reduce cardiovascular disease and events among firefighters.

Study in Progress
To provide further understanding of firefighters and their risk for CVD, we have initiated a study of firefighters in North Carolina, with attention to lifestyle; traditional risk factors, including standard lipid profiles; "advanced lipid testing" assessing for "discordance" and risk not recognized by traditional low-density lipoprotein cholesterol (LDL-C) levels, and markers of inflammation. We hope to report our findings soon.

Final notes and Recommendations
Considering the number of firefighters across the country, all clinicians are likely to encounter firefighters in their practices. Lipid specialists should be aware of the cardiovascular risk that exists among firefighters and be familiar not only with the traditional risk factors among firefighters but also those occupational risks that are unique to these public servants. Additional research is critically needed to determine what, if any, cost-effective strategies might be implemented to more accurately identify those firefighters at risk and, if possible, reduce that risk.

Acknowledgements
The author wishes to thank Michelle Beidelschies, PhD, of Cleveland HeartLab, Inc., and Debbie Winegar, PhD, of LipoScience Inc. for their editorial assistance and support of on-going research, and all firefighters and their families for their dedication and sacrifices on our behalf.

Disclosure statement: Dr. White has served on the speakers bureau for AbbVie, Amarin, Liposcience and Vivus and is a stockholder in Isis.