By KARLIE MOORE
Nearly 50 percent of firefighter line-of-duty deaths (LODDs) result from heart attacks. A great deal of scientific research clearly illustrates that these cardiovascular events do not happen at random. Indeed, the majority occur during very physically strenuous situations such as fire suppression. Further, almost all firefighters who experience these events possess one or more of the risk factors for cardiovascular disease (CVD).1 These risk factors are obesity, diabetes, high cholesterol, high blood pressure (hypertension), and inactivity or low cardiorespiratory fitness. In terms of heart attacks, people are also at greater risk as they become older and if they had a parent experience a heart attack at a young age.2
Although risk for heart attacks among firefighters is dependent on many factors, the most compelling explanation for the high incidence of cardiovascular events is the extreme physical demand of firefighting coupled with the presence of CVD risk factors in those who experience these events. In addition, high temperatures present during fire suppression significantly increase physiological strain and the potential to overexert the cardiovascular system. Chronic psychological stress brought on by tending to emergency situations and exposure to pollutants also increase risk by promoting inflammation in the body and the development of CVD risk factors. (1)
Encouragingly, possessing high cardiorespiratory fitness significantly reduces firefighters’ risk of experiencing a cardiac event. Further, chronic stress and CVD risk factors can be mitigated by engaging in other healthy habits. (1) Therefore, firefighters must understand the degree to which and how they can reduce their risk of suffering a heart attack on the job.
One particularly problematic risk factor for CVD is hypertension; it has been nicknamed “The Silent Killer” because it usually cannot be felt, yet it is the cause of many unexpected strokes and heart attacks. Data illustrate that hypertension increases the risk of LODDs significantly and to a greater degree than other risk factors.3 Even more concerning is that contemporary data suggest that firefighters often fail to monitor their own blood pressures despite routinely measuring the blood pressure of others.4 Since, as will be discussed, being hypertensive is a real danger to firefighters, more attention should be brought to this issue so firefighters are aware of the importance of knowing their blood pressure values. Also, there is some general misunderstanding about the causes of and best treatment for hypertension. This article discusses the real causes and consequences of hypertension in firefighters and provides some strategies for avoiding/managing it.
DANGERS OF HYPERTENSION IN FIREFIGHTERS
Hypertension is characterized by a greater than normal force of blood pushing against the walls of the arteries. Optimal blood pressure is a systolic pressure lower than 120 mmHg (millimeters of mercury) and a diastolic pressure lower than 80 mmHg. According to the National Heart, Lung and Blood Institute, individuals are “prehypertensive” if their systolic blood pressure ranges between 120 and 139 mmHg or if their diastolic blood pressure ranges between 80 mmHg and 89 mmHg. Those who have prehypertension should adopt lifestyle modifications (discussed later) to reduce their blood pressure. However, antihypertensive medications are not indicated. Stage 1 hypertension is characterized by a systolic blood pressure of between 140 mmHg and 159 mmHg or a diastolic blood pressure of between 90 mmHg and 99 mmHg. Lifestyle modifications and a thiazide-type diuretic are recommended for most people who possess stage 1 hypertension.
Stage 2 hypertension is characterized by a systolic blood pressure greater than 160 mmHg or a diastolic pressure greater than 100 mmHg. For many people who have stage 2 hypertension, a combination of two medications and lifestyle modifications is necessary. Treatment with medication may be more aggressive if other complications exist such as heart failure, prior heart attack, diabetes, kidney disease, or a high risk for CVD or stroke. The target blood pressure for a person undergoing treatment for hypertension is a systolic pressure of less than 140 mmHg and a diastolic pressure of less than 90 mmHg; if that person has diabetes or kidney disease, the goal is a systolic pressure of less than 130 mmHg and a diastolic pressure of less than 80 mmHg.5
Hypertension can lead to enlargement of the heart and heart failure, aneurysms, narrowing of the blood vessels in the kidney and kidney failure, and hardening of the arteries, which can result in heart attack and stroke; it is also associated with poor cognitive functioning in old age. People who are hypertensive in middle age are much more likely to have deficits in memory, problem solving, concentration, and judgment. Further, this loss of cognitive abilities diminishes one’s capacity to live independently in old age.6
Among the general population, long-term research has illustrated that risk of CVD-related death rises dramatically as systolic blood pressure increases. (6) For firefighters, even in the absence of hypertension, the risk of heart attack is higher than that for the average person. During physically and mentally stressful situations, firefighters’ heart rates and stroke volumes rise in response to adrenaline release, which increases the demand on the heart. Accordingly, heart attack risk is inherently higher during physically demanding emergency tasks; some research has shown that firefighters are 64 times more likely to experience a heart attack during fire suppression compared with nonemergency tasks. (3) Thus, for firefighters who are hypertensive, the load on the heart increases dramatically, as does the potential for heart attack; it must overcome the high pressure exerted from the arteries. This is supported by recent reports on firefighter fatalities from the National Fire Protection Association. In 2011, there were 31 sudden cardiac deaths among U.S. firefighters. Of the 22 victims whose medical information was available, 13 (59 percent) were hypertensive.7 In 2012, 27 U.S. firefighters suffered sudden cardiac events; the autopsy results for 20 of them showed that 14 (70 percent) were hypertensive. Many of these firefighters also exhibited other risk factors including obesity, smoking, high cholesterol, diabetes, atherosclerosis, and a history of cardiac problems.8
To understand the impact of CVD risk factors on heart attack risk in firefighters, Kales and colleagues investigated the autopsies of 52 firefighters whose cause of death was related to cardiac heart disease (CHD), an advanced form of CVD (although the terms are often used interchangeably). (3) Most CVD-related deaths (90 percent) in firefighters are caused by CHD. Using information from 310 active firefighters as a control, the study determined that a firefighter is 12 times more likely to die a CHD-related death if he is hypertensive (all the subjects in the study were males). This increase in risk is greater than that posed by diabetes, smoking, and high cholesterol, which deem a firefighter 10.2, 8.6, and 4.4 times, respectively, more likely to die of a CHD-related death.
If a firefighter had a prior diagnosis of CHD, then the risk of a CHD death was 35 times more likely. However, only 26 percent of the 52 deceased firefighters had a prior CHD diagnosis. Thus, it is imperative to monitor CVD risk factors rather than simply rely on a physician’s diagnosis of CHD to determine whether the individual is safe to fight fire. Low cardiorespiratory fitness is also a well-established risk factor for CVD/CHD and could present an even greater risk than hypertension, but that information was not known among these firefighters. Also, those more than 45 years old were 18.4 times more likely to die of CHD, and those more than 50 years old were 22.8 times more likely to die of CHD.
The researchers also compared CVD risk factors among 113 firefighters who experienced nonfatal cardiac events and 90 firefighters who died from cardiac events. They found that, again, hypertension increased the risk of dying from a cardiac event to a greater degree than high cholesterol and diabetes. The odds of the cardiac event resulting in death were 2.2 times more likely for each of the following risk factors: hypertension, current smoking, and obesity.
CAUSES OF HYPERTENSION
The effect of weight on blood pressure. The causes of many cases of hypertension are unknown. However, research has shown that among the general population, blood pressure rises linearly as body weight increases. In fact, overweight individuals are two to six times more likely to suffer from hypertension, and risk rises progressively with increasing weight. (6) Data from the Framingham Heart study, one of the largest and longest-running investigations of cardiovascular health, suggest that obesity accounts for 78 and 65 percent of the overall risk of developing hypertension in males and females, respectively.9
In the United States, the prevalence of high blood pressure also rises as the population becomes older. In fact, the current trend reveals that middle-aged individuals (55 years) have a 90-percent risk of developing hypertension throughout the remainder of their lives. However, other countries where obesity is not an epidemic do not exhibit this trend. Therefore, the relationship between rising blood pressure and age in the United States should not be attributed to the aging process alone; rather, it is the age-associated increase in body weight that explains the corresponding increase in blood pressure. Furthermore, even those who develop obesity at a young age (children and adolescents) suffer from hypertension. (6)
Sleep apnea and hypertension. Another known cause of hypertension, also associated with being overweight, is obstructive sleep apnea (OSA). Approximately 24 percent of middle-aged men and nine percent of women suffer from OSA, a condition in which the upper airway collapses with inspiration during sleep, resulting in decreased respiration and oxygen saturation. This lapse in breathing causes an immediate spike in blood pressure, which appears to persist throughout the waking hours. Indeed, studies have illustrated that people with OSA are more likely to have hypertension, independent of body weight. Moreover, OSA has been shown to be a predictor of the development of CVD in men. (9)
Firefighters sleeping in quarters together may be able to recognize when a person exhibits longer than 10-second delays in breathing that are symptomatic of OSA. Other OSA signs include very shallow breathing, snoring, and daytime fatigue. Since people who suffer from OSA often do not recognize that they are having difficulty breathing during sleep, firefighters must recognize these signs in others. Firefighters especially may associate their daytime sleepiness to other factors since they are chronically sleep deprived. Unfortunately, people often suffer from OSA for years before being treated.
The primary treatments for OSA are use of continuous positive airway pressure (CPAP) during sleep and weight loss. While CPAP effectively treats OSA, it also readily reduces blood pressure. Since obesity is the strongest risk factor for OSA, even a small amount of weight loss has been shown to lessen the occurrence of OSA. Furthermore, there appears to be a reciprocal relationship between obesity, OSA, and hypertension. Although obesity can result in OSA, the same is true in reverse: Developing OSA can lead to weight gain since lack of sleep is associated with a hormonal shift that induces hunger. Therefore, avoiding obesity is effective at reducing the risk of OSA and hypertension. For individuals who suffer from OSA, proper diagnosis and treatment are equally important to halt OSA-induced hypertension and weight gain. (9)
The myth of salt intake. The effect that salt intake has on blood pressure is misunderstood. The theory that eating salt causes blood pressure to rise originated from the observation that populations who ate more salt had a higher incidence of hypertension compared with those with lower salt intakes. But those populations with high salt intake exhibited an unhealthy diet of high fat and packaged/processed food while being low in fruits, vegetables, and fiber. Now, scientists estimate that no more than half of all hypertension cases are actually the result of high salt intake. Only people who are “salt sensitive” will experience a rise in blood pressure from eating salt; they will also experience a drop in blood pressure in the absence of salt. Unfortunately, there is no simple test for salt sensitivity.10 However, the National Heart, Lung and Blood Institute still recommends that people limit their dietary sodium intake to 2,400 milligrams per day to prevent hypertension.
TREATMENT OF HYPERTENSION
Research clearly illustrates that losing weight is the single most effective strategy for reducing blood pressure. For every kilogram (2.2 pounds) of weight loss, systolic blood pressure lowers by 1.6 mmHg while diastolic pressure lowers by 1.1 mmHg on average. (6) Therefore, the more weight lost, the greater the reduction in blood pressure.
Other effective lifestyle changes are reducing sodium intake (effective for those who are salt sensitive), limiting alcohol consumption to two drinks per day, and exercising. Moderate and high-intensity exercise has been shown to decrease blood pressure, with greater effects as the volume of exercise increases. Exercise promotes vasodilation and relaxation of the arteries, thereby reducing the pressure exerted back on the heart. A beneficial drop in blood pressure occurs immediately following and up to 24 hours after exercising. People who begin an exercise program can expect a decrease of up to eight mmHg in blood pressure within the first few weeks. If exercise is maintained for longer than three months, one can expect even further reductions. Exercise also indirectly reduces blood pressure by promoting weight loss. (6)
With regard to diet, several minerals are recommended for the treatment of hypertension. They include calcium, magnesium, and potassium. Potassium is found in many fruits and vegetables; magnesium levels are high in leafy greens, nuts, beans, and grains. The DASH (Dietary Approaches to Stop Hypertension) diet has been shown to be effective at treating hypertension. It is high in fruits, vegetables, whole grains, and low-fat dairy products and is, therefore, abundant in these three minerals as well as fiber. Just like exercising, eating a healthful diet indirectly reduces blood pressure by promoting weight loss. (6)
The National Heart, Lung and Blood Institute recommends lifestyle changes as the first line of defense against high blood pressure. Medication may be prescribed if lifestyle changes alone do not result in normalizing blood pressure. One study investigated the difference in blood pressure reduction when implementing lifestyle changes alone (weight loss, sodium reduction, and exercise) vs. lifestyle changes in addition to medication. In 900 people with hypertension who participated in the study for a year, those who implemented lifestyle changes alone experienced a reduction of 10.6 mmHg in systolic pressure and 8.1 mmHg in diastolic pressure; those who took medication in addition to implementing the lifestyle changes experienced a 19 mmHg reduction in systolic blood pressure and a 13 mmHg reduction in diastolic blood pressure.11
Given the dangers of being hypertensive while on the fire line, controlling blood pressure should be firefighters’ number-one health-related goal. Everybody will experience a decline in blood pressure by eating healthfully, exercising regularly, and achieving a healthy weight. Take medication in addition to these lifestyle changes if further reductions in blood pressure are still necessary.
REFERENCES
1. Soteriades ES, Smith DL, Tsismenakis AJ, et al. Cardiovascular disease in US firefighters: a systematic review. Cardiol Rev. 2011;19(4):202.
2. American Heart Association. Understand your Risk of Heart Attack. Am Heart Assoc. 2012. Available at: www.heart.org/HEARTORG/Conditions/HeartAttack/UnderstandYourRiskofHeartAttack/Understand-Your-Risk-of-Heart-Attack_UCM_002040_Article.jsp. Accessed September 19, 2012.
3. Kales SN, Soteriades ES, Christoudias SG, et al. Firefighters and on-duty deaths from coronary heart disease: a case control study. Environ Health. 2003;2(1):14.
4. Davila EP, Kuklina EV, Valderrama AL, et al. Prevalence, Management, and Control of Hypertension among US Workers: Does Occupation Matter? J Occup Environ Med. 2012;54(9):1150–1156.
5. Chobanian AV, Bakris GL, Black HR, et al. Seventh report of the joint national committee on prevention, detection, evaluation, and treatment of high blood pressure. Hypertension. 2003;42(6):1206–1252.
6. Nieman D. Exercise Testing & Prescription. 7th ed. McGraw-Hill Humanities/Social Sciences/Languages; 2010.
7. Fahy R, Leblanc PR, Molis JL. National Fire Protection Association: Firefighter Fatalities in the United States. Available at: www.nfpa.org/assets/files/PDF/osfff.pdf. 2011.
8. Fahy R, LeBlanc P, Molis J. Firefighter Fatalities in the United States, 2012. NFPA J. 2013. Available at: http://www.nfpa.org/newsandpublications/nfpa-journal/2013/july-august-2013/features/firefighter-fatalities-in-the-united-states-2012.
9. Wolk R, Shamsuzzaman ASM, Somers VK. Obesity, Sleep Apnea, and Hypertension. Hypertension. 2003;42(6):1067–1074.
10. Thompson J, Manore M, Vaughan L. The Science of Nutrition. San Francisco, CA: Pearson Benjamin Cummings. 2011.
11. Group T of MHR. The treatment of mild hypertension study: a randomized, placebo-controlled trial of a nutritional-hygienic regimen along with various drug monotherapies. Arch Intern Med. 1991;151(7):1413–1423.
KARLIE MOORE has a PhD in exercise science and nutrition from Oregon State University. She has dedicated her research and worked to help firefighters improve their health so they can live long, happy lives. Moore conducts comprehensive fitness assessments for several fire departments in Oregon and speaks on topics related to firefighter health. She is also a part-time professor at Oregon State University.
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