Cardiovascular Risk Factors Among Career Firefighters. by Dana C. Drew-Nord, PhD, APRN, BC, OiSaeng Hong, PhD, RN, and Erika S. Froelicher, PhD, RN

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Continuing education Phyllis Berryman, RN, MBA, COHN-S/CM, FAAOHN Eileen Lukes, PhD, RN, COHN-S, CCM, FAAOHN Cardiovascular Risk Factors Among Career Firefighters by Dana C. Drew-Nord, PhD, APRN, BC, OiSaeng
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Continuing education Phyllis Berryman, RN, MBA, COHN-S/CM, FAAOHN Eileen Lukes, PhD, RN, COHN-S, CCM, FAAOHN Cardiovascular Risk Factors Among Career Firefighters by Dana C. Drew-Nord, PhD, APRN, BC, OiSaeng Hong, PhD, RN, and Erika S. Froelicher, PhD, RN research abstract Sudden cardiac death is the leading cause of on-duty death among firefighters. Determining firefighters risk of cardiovascular death or all-cause mortality, cardiovascular risk factor profiles, and energy demands while firefighting may aid in understanding why this occupational group is at risk for on-duty sudden cardiac death. A literature review conducted between 2006 and 2009 did not demonstrate that firefighters are at increased risk of all-cause death compared to the general population. In addition, cardiovascular risk profiles of firefighters are similar to those of the general population. Firefighters may be part of the national obesity epidemic; their hypertension and hypercholesteremia often are not diagnosed or are undertreated. The combination of personal cardiovascular risk factors and extreme physical work demands may contribute to sudden cardiac death in this population. North American firefighters are predominately males who are relatively young (53.7% are 20 to 39 years old, 41.3% are 40 to 59 years old, and 5% are older than 60 years) (U.S. Fire Administration, 2007). Many retire between 50 and 55 years of age due to the extreme physical demands of firefighting, but are also encouraged by incentives for early retirement. The public has significant expectations of these servants, the most basic of which are that firefighters will focus on About the Authors Dr. Drew-Nord is Adjunct Assistant Professor, Occupational and Environmental Health Nursing, Community Health Systems; Dr. Hong is Professor, Occupational and Environmental Health Nursing; and Dr. Froelicher is Professor, Physiological Nursing, University of California, San Francisco, School of Nursing. The authors disclose that they have no significant financial interests in any product or class of products discussed directly or indirectly in this activity, including research support. Ms. Berryman is Senior Consultant, Medical Management, Integrated Disability Management Department, FinCor Solutions, Lansing, MI. Dr. Lukes is Health Services Southern Regional Manager, The Boeing Company, Mesa, AZ. doi: / safety for themselves, their colleagues, and the community. Between 1994 and 2004, 368 on-duty firefighters died (excluding those who died at the World Trade Center) among 316,950 career firefighters in the United States (Centers for Disease Control and Prevention [CDC], 2006). The cost of these deaths includes the emotional toll on families and colleagues, work force deficit, loss of knowledge, and direct financial impact on the community and families. Of these deaths, 39% were heart attacks, 29% other causes (e.g., burns, cerebral vascular accident, or drowning), 20% asphyxiation, and 12% motor vehiclerelated trauma (CDC). Given the significant number of firefighter deaths related to cardiovascular disease (CVD), it is necessary to identify risk factors and develop intervention programs to prevent or reduce fatalities through early detection and treatment. The purpose of this study was to identify CVD risk factors among firefighters through an extensive literature review. Specifically, this review answers three questions: 1. What are the energy demands imposed by firefighting? OCTOBER 2009, vol. 57, no Applying Research to Practice U.S. firefighters do not appear to benefit from the healthy worker effect, may be part of the national obesity epidemic, and have cardiovascular risk profiles similar to the general population. Demanding work, heavy gear, and occlusive clothing, combined with the emergent nature of fire and rescue situations, may place firefighters at increased risk for cardiovascular events, especially if undiagnosed or undertreated cardiovascular disease exists. Hypertension and hypercholesteremia are significantly undertreated in this population. Occupational health nurses can be the education and communication facilitators for firefighters and primary care providers who may not be aware of the increased cardiovascular risks potentially associated with firefighting demands. Occupational health nurses are uniquely positioned to assess cardiovascular risks and implement programs to reduce these risks among career firefighters. 2. What is the CVD risk profile of firefighters? 3. Are firefighters at greater risk for all-cause or cardiovascular mortality? METHOD An extensive literature review (2006 to 2009) was conducted using several library databases, including PubMed and the Cumulative Index of Nursing and Allied Health Literature (CINAHL). Keywords used included firefighter, male, sudden cardiac death, mortality, cardiovascular, obesity, hypertension, lipids, aging, fitness, and occupational health. This review was limited to peer-reviewed studies published in English and excluded female career firefighters. A consideration when discussing firefighter mortality is the impact of the healthy worker effect (HWE). The HWE is an observed decrease in mortality in workers when compared to the general population (Choi, 1992, p. 980). Standardized mortality ratio (SMR) is an indirect age adjustment statistic used to compare death rates due to a specific cause between an occupational group and the general population (Gordis, 2004). An SMR of 100 is equal risk between groups; less than 100 indicates fewer deaths than expected; and more than 100 indicates more deaths than expected (Gordis). The HWE generally accounts for a 20% to 30% reduction in mortality in SMRs (Choi). Findings Findings of the literature review are organized to answer the three questions. 1. What are the energy demands imposed by firefighting? Efforts to define work energy demands of firefighting have focused on determining the metabolic equivalent (MET) levels required to safely perform fire suppression duties. A MET is a multiple of the resting metabolic rate and is commonly estimated using standardized equations (Froelicher & Myers, 2006). The range of METs suggested or observed in the literature is from 9.6 (Sothmann, Saupe, Jasenof, & Blaney, 1992) to 14 (Malley et al., 1999). Ten METs is roughly equivalent to jogging a 10-minute mile; 14 METs is similar to extended activities such as running or rowing competitively, or bicycle racing at a high level (Fletcher, Froelicher, Hartley, Haskell, & Pollock, 1990). A comparison of heart rates, with varying weights of self-contained breathing apparatus during simulated fire drills, found that heart rate increased to 70% to 80% of maximum predicted within the first minute of the exercise, regardless of type or weight of breathing gear. Heart rate continued to increase to 90% to 100% of predicted maximum and remained there until the fire was extinguished (Manning & Griggs, 1983). Maximum heart rate and VO 2 max were compared for firefighters who performed maximal work on a stairclimbing machine versus a treadmill. VO 2 max is the maximum volume of oxygen that an individual can process with aerobic metabolism. VO 2 max, also known as peak VO 2, is an objective, clinical measure that defines the limits of cardiopulmonary function. Peak VO 2 directly reflects individuals ability to increase their heart rate and stroke volume and redirect oxygenated blood to muscles for work on demand. Exercising at a level beyond which the cardiopulmonary system can adequately supply oxygen (commonly termed the anaerobic or ventilatory threshold, or VT) involves a greater degree of oxygen-independent muscle metabolism, which is dramatically less efficient than aerobic metabolism, and can compromise cardiovascular function (Froelicher & Myers, 2006). The stair-climbing machine resulted in significantly lower VO 2 max and maximum heart rate without wearing personal protective equipment (PPE) (Ben-Ezra & Verstraete, 1988). Similarly, 10 firefighters completed submaximal treadmill tests with VO 2 max measurements; they then completed a set of simulated tasks in PPE (Sothmann et al., 1991). Although heart rate with suppression tasks was not significantly different from heart rate at exhaustion on the treadmill, VO 2 max with simulated suppression tasks was significantly less than predicted by the treadmill (Sothmann et al.). Researchers and firefighters collectively determined the most strenuous tasks in firefighting (reported in order of difficulty) as (1) carrying equipment up stairs in a high-rise building; (2) advancing charged hoses; (3) breaking down doors, walls, ceilings, and roofs; (4) raising ladders; (5) working overhead; and (6) rescuing victims (Gledhill & Jamnik, 1992). The most difficult tasks (i.e., numbers 1 and 2) required 11.9 METs, representing 85% of VO 2 max (Gledhill & Jamnik). The less arduous tasks (i.e., numbers 5 and 6) required 6.6 METs, which represented 50% of VO 2 max (Gledhill & Jamnik). Another study compared task simulations in three uniforms to a baseline maximum stress treadmill and ac- 416 AAOHN Journal tual VO 2 max measured in workout clothes (Malley et al., 1999). Each firefighter repeated a treadmill test to exhaustion on three separate occasions, wearing three separate uniforms (traditional, modern, and modified modern), including PPE. Regardless of uniform type, each firefighter surpassed his anaerobic threshold at 1 minute, 70% of his VO 2 max by 3 minutes, and 90% of his VO 2 max by the end of the exercise and reached his maximum heart rate (Malley et al.). This study showed a negative relationship between age and VO 2 max, and that uniform type influenced exercise time significantly. In contrast to objective measurements, self-perception of fitness and measured aerobic capacity did not demonstrate a relationship (Peate, Lundergan, & Johnson, 2002). A total of 92 firefighters completed a self-assessment of their fitness level and had VO 2 max estimated from two tests (5-minute step test and submaximal stress treadmill). No association was found between the firefighters self-perception of fitness and estimated aerobic capacity (Peate et al.). Twelve firefighters randomly exercised on graded treadmills to exhaustion in workout clothes, and then in full PPE. VO 2 max was 17.3% lower in the PPE than in the workout clothes (Dreger, Jones, & Petersen, 2006). All of these studies reinforce the concept that the energy demands of firefighting are significant. Studies of the accuracy of firefighters self-perceptions of effort remain inconclusive. 2. What is the CVD risk profile of firefighters? Overall Firefighter Cardiovascular Risk Profiles. The RISKO cardiac index (Michigan Heart Association, 1967) was calculated for 4,066 Los Angeles County safety personnel, of whom 1,825 were firefighters. Compared to lifeguards, marshals, and sheriffs, firefighters had the second lowest risk score despite being the oldest cohort (Thomas, Cady, O Connell, Bischoff, & Kershnar, 1979). In 1982, firefighters were matched to veterans enrolled in the Normative Aging Study in Boston and monitored for 10 years (Dibbs, Thomas, Weiss, & Sparrow, 1982). The firefighters were at lower risk for developing CVD than the comparative population of veterans (Dibbs et al.). Of the 43 on-duty firefighter deaths in North Carolina between 1972 and 1985, 23 were due to CVD (Fort & Griggs, 1987). Only 6 of the 23 victims had a history of CVD, highlighting the need for early identification and intervention. In a study by Licciardone et al. (1989), 452 firefighters in Dallas, Texas, with ages ranging from 18 to 59 years, completed physical examinations, serum chemistry and lipid profiles, resting and exercise stress electrocardiograms (ECGs), and body fat assessment. Hypercholesteremia and obesity were commonly found, but Framingham Risk Equations (National Institutes of Health, National Heart, Lung and Blood Institute, 2005) of the cohort did not differ from those of age-matched men in the general population (Licciardone et al.). Between 1984 and 1992, 806 Cincinnati firefighters participated in comprehensive periodic examinations, including a thallium treadmill (Glueck et al., 1996). This study found that firefighting was not associated with an increase in cardiovascular event rates. CVD was related to modifiable risk factors (i.e., blood pressure, cholesterol, and cigarette smoking). No relationship was found between smoke inhalation during fire suppression and cardiovascular death. The most-studied firefighter cohort to date is from Massachusetts. There, the relationship between cardiovascular risk factors and fitness for duty was explored among Hazardous Material (HazMat) firefighters (Kales, Aldrich, et al., 1999). The study found that lower predicted aerobic capacity (VO 2 max) and lower spirometric function, combined with an increase in age, cholesterol, and weight, resulted in increased cardiovascular risk. More important, the findings underscore that not one indicator but often multiple factors predispose firefighters to CVD. In a 2003 case-control study using national data, 52 cardiovascular on-duty deaths were compared to 51 noncardiovascular on-duty deaths between 1996 and 2002 among the male subjects of the HazMat cohort from Massachusetts (n = 310) (Kales, Soteriades, Christoudias, & Christiani, 2003). An important finding was the time of cardiovascular death: firefighters most often had cardiac death between noon and midnight, whereas the general population most frequently dies of cardiovascular events between 6 a.m. and 12 p.m., regardless of work shift pattern. The time of firefighter death corresponds to the period of high-intensity emergency dispatches in most fire departments. The second significant finding was the increased odds of firefighter cardiac death being associated with fire suppression activities (Kales et al.). Traditional risk factors (i.e., age, smoking, diabetes, and hypertension) were found more frequently among the victims of cardiovascular death than the controls. Firefighter Framingham risk equation scores (based on a one-time physical examination and laboratory evaluation) were compared to Framingham risk equation scores of an age-matched healthy group (same age, optimal blood pressure, total cholesterol between 160 and 199 mg/dl, high density lipoprotein [HDL] 45 mg/dl, no diabetes, and no history of smoking). The percentage of firefighters exceeding the low coronary heart disease risk category for each factor ranged from 40% to 87% (Byczek, Walton, Conrad, Reichelt, & Samo, 2004). As a group, firefighters had a higher prevalence of obesity, lower HDL, higher low-density lipoprotein (LDL), and higher total cholesterol than the healthy group (Byczek et al.). Comparing 362 Massachusetts firefighters, members of the Massachusetts HazMat cohort who qualified for heart presumption retirements, a compensable workers compensation injury or illness, between 1997 and 2004, researchers concluded that of the retirement group, 42% of the retirements were related to on-duty events (Holder, Stallings, Peeples, Burress, & Kales, 2006). Retiree cardiovascular risk factors (i.e., age, current cigarette smoking, diabetes, or prior arterial occlusive disease) were OCTOBER 2009, vol. 57, no all independent significant predictors of heart disease presumptive retirement, with age being the strongest predictor. This analysis also determined that the risk of an on-duty event was highest during fire suppression activity (odds ratio [OR] = 51; 95% confidence interval [CI] = 12, 223) (Holder et al.). When the relationship between firefighter activity and risk of a cardiac event is examined, only 1% to 5% of firefighters time on task is spent on actual fire suppression, although the majority of cardiac events occur during suppression activities. Cardiovascular line-of-duty death (LODD) was associated with fire suppression (32.1%); responding to an alarm (13.4%); returning from an alarm (17.4%); engaging in physical training (12.5%); attending non-fire emergencies (9.4%); and performing nonemergency duties (15.4%) (Kales, Soteriades, Christophi, & Christiani, 2007). The seasonality of firefighter cardiovascular LODD does not appear to match the seasonality of cardiovascular death in the U.S. population for spring and summer but does for winter (Mbanu et al., 2007). When type of duty preceding death was included in the analysis over time of year of death, the risk of fire suppression-related on-duty death is highest in winter (32%), lowest in spring (15%), spikes to 30% in summer, and is 23% in fall. Eighty-seven acute on-duty cardiovascular deaths occurred among all firefighters between 1996 and 2006 (National Institute for Occupational Safety and Health, 2007). The cardiovascular risk profile of this group was compared to 113 firefighters who experienced a non-fatal, on-duty, career-ending cardiovascular event in Massachusetts between 1997 and 2004 to determine any specific predictors of a fatal cardiovascular event. Current smoking, hypertension, and previous diagnoses of CVD, carotid stenosis, or peripheral arterial disease were significant predictors of a fatal outcome in on-duty events (Geibe et al., 2008). Obesity. A commonly used formula for determining obesity is the body mass index (BMI) (body weight in kilograms divided by height in meters squared) (McPhee & Pignone, 2005). The majority (87%) of the Massachusetts HazMat cohort had a BMI over 25, with 34% over 30 (Kales, Polyhronopoulos, Aldrich, Leitao, & Christiani, 1999). The mean BMI was 28.9, which is above the 85th percentile for men based on the National Health and Nutritional Examination Survey II data (NHANES II; Van Itallie, 1985). Given the limitation of BMI to distinguish between fat and muscle mass (Jette & Sidney, 1990), this percentage seems to indicate that a higher proportion of firefighters are obese than the general population (Kales, Polyhronopoulos, et al.). Analysis of Texas firefighters yielded similar results (Clark, Rene, Theurer, & Marshall, 2002). On the basis of BMI criteria proposed by the World Health Organization (2008), 80% of the sample was classified as being overweight to obese (BMI 25). With the standard criteria of Kales, Polyhronopoulos, et al. (1999), 60% were classified as obese. Allowing a BMI of 25 to 26.9 to represent increased muscle mass, the majority of these firefighters (mean BMI = 28.8) remain above the 85th percentile of the general population (Kales, Polyhronopoulos, et al.). At baseline, the average BMI of the HazMat cohort was 28.9 (± 4.1) (Kales, Polyhronopoulos, et al., 1999); after 5 years, it increased by 0.8 to 29.7 (± 4.3) (Soteriades et al., 2005). The prevalence of obesity (BMI 30) increased significantly during the study period, from 34.9% in 1996 to 1997 to 39.7% in 2001; more important, extreme obesity (BMI 40) increased fourfold during the same period (Soteriades et al.). Cardiovascular risk factors (i.e., age, smoking, hypertension, increased total cholesterol or LDL, decreased HDL, and increased fasting glucose) were also associated with weight increase. Analysis of obesity and job disability in the HazMat cohort demonstrated that for every unit increase in BMI, an associated 5% increase in risk of job disability occurred (Soteriades, Hauser, Kawachi, Christiani, & Kales, 2008). Obesity has previously been linked to cardiovascular events at work; it may also place firefighters in danger of acquiring non-cardiac, career-ending disabilities. The national obesity epidemic is reflected in firefighter and emergency medical response recruits. Of 370 firefighter (n = 210) and ambulance (n = 160) recruits (age range of 18 to 34 years) examined in Massachusetts between 2004 and 2007, 43.8% were overweight (BMI = 25 to 29.9) and 33% were obese (BMI 30) (Tsismenakis et al., 2009). Of equal concern is the significant association between increased BM
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