Cancer in the fire service is a critical issue. The National Institute for Occupational Safety and Health (NIOSH) found that firefighters have a 9 percent increase in cancer diagnosis and a 14 percent increase in cancer-related death as compared to the general population.1 While those numbers may not appear too startling, one must also consider that, while firefighters’ overall cancer diagnoses do not far outpace the general public, their diagnosis of particular types of cancers does.2 With that in mind, it is important for us to consider anything contributing to firefighter cancer.
The fire service has done considerable research to determine the causes of firefighter cancer. Among the causes are smoke, contaminants in our hoods and microscopic particulates left behind on our gear. Studies have been done to see how we may be spreading this particulate matter around apparatus cabs and the firehouse. Efforts are underway to evaluate the effectiveness of on-scene gross decontamination, storing gear and air packs in apparatus compartments, showering immediately upon returning from a fire, and “sweating out” carcinogens that may be trapped on the skin. While the fire service is taking cancer seriously, it needs to consider the effects of chronic stress as a contributor to firefighter cancer.
The stress response
Is stress always a bad thing? Definitely not. In fact, stress can be essential to our survival. When we encounter an acute stressor, our bodies undergo a rapid process of events, including the secretion of epinephrine and norepinephrine, designed to trigger our “fight or flight” response. As this initial surge of epinephrine and norepinephrine subsides, the body may want to stay on heightened alert. When this occurs, the second part of the stress response is activated. This second phase activates the hypothalamus, the pituitary gland and the adrenal glands (HPA axis). When the HPA axis is activated, the hypothalamus releases corticotropin-releasing hormone (CRH). The CRH goes to the pituitary gland, which then secretes adrenocorticotropic hormone (ACTH). Finally, the ACTH triggers the adrenal glands to release cortisol. When the threat passes, the parasympathetic nervous system takes over, and cortisol levels fall. An issue firefighters face, however, is that they often suffer from chronic stress, and chronic stress can keep cortisol, epinephrine and norepinephrine levels abnormally high.
Chronic stress at work and at home
There are numerous causes of chronic stress in the fire service. First, firefighters are constantly on alert while on shift. If you compare the way you take a shower at the firehouse versus the way you take a shower at home, it becomes clear that firefighters constantly feel the pressure of a potential quick response on duty.
Stress isn’t necessarily left at the firehouse at shift change, either. Most firefighters can recall sitting at home with a television on in the background and a song or commercial coming on that makes a sound like the firehouse tones. When this occurs, firefighters reflexively snap into “response mode” even though they are nowhere near the firehouse. Speaking of the firehouse, consider run loads. Every time the tones sound, firefighters have an acute and potentially chronic stress response to prepare them for the upcoming “fight.” In a busy firehouse, this fight or flight response adds up. After some time, the firefighter’s blood will have more cortisol, epinephrine and norepinephrine in it than it needs.
One other stress factor to consider is sleep deprivation. All firefighters know that it is incredibly difficult to sleep at the firehouse. They have the non-stop readiness to respond coupled with snoring, CPAP machines, people getting up to use the bathroom, cell phones buzzing, someone’s bunk light being on, waking up for your calls, that one person who always talks in their sleep, and on and on. This disrupts circadian rhythms and increases chronic stress. Additionally, due to our heightened alertness at the firehouse, if a firefighter is startled awake, he or she will likely get another dump of epinephrine and norepinephrine, which both increases blood levels of those hormones and makes it harder to fall back asleep. There are many more examples of chronic stressors in the fire service, but these common examples sufficiently demonstrate that it is a pervasive issue.
Looking at the studies
Having discussed the presence and some causes of potentially abnormal levels of cortisol, epinephrine and norepinephrine in firefighters due to chronic stress, let’s examine how cortisol affects the immune system. Cortisol acts as an anti-inflammatory agent in the body, and it also acts on most immune system cells, especially lymphocytes.3 When too much cortisol is present, it causes lymphocytes to die sooner, and it also impedes lymphocyte reproduction.4 This results in an overall reduction in immune system functioning due to increased immune cell destruction and decreased immune cell reproduction. These types of chronically elevated cortisol levels, along with an abundance of epinephrine and norepinephrine, can depress the entire immune system. So how does this all relate to cancer?
While it is not the position of this article that stress causes cancer, “chronic stress … can help cancer grow and spread in a number of ways.”5 To that end, studies are limited, but some efforts have been made to examine the effects of stress on the immune system and how those effects potentially promote cancer growth.
A recent study of acute myeloid leukemia (AML) discovered that cortisol plays a vital role in overriding the immune system. They found that cortisol causes the release of the protein latrophilin 1, which in turn causes the release of a second protein in the blood. The second protein, called galectin-9, actually suppresses the body’s natural anti-cancer immune system.6 Malignant AML cells are able to use cortisol to increase the release of latrophilin 1 to avoid the immune system. As a result, the presence of cortisol in the blood assists with the spread of AML in the human body via immuno-suppression.
Researchers also evaluated how stress impacts T-cell quantities and functions in rats. Some T-cells are designed to locate and destroy cancer cells through a process called mitogen responsiveness. The study found that stress impeded the T-cells from secreting a chemical called IL-2 that affected mitogen responsiveness. “This is important because defective IL-2 production could also lead to significant impairment of immunoregulatory T-cell generation and thus a predisposition to malignancy …”7 As a result, chronic stress can promote the spread of cancer due to the lack of T-cell protection.
Another study concluded that chronic stress promotes cancer establishment and spread by depressing T-cell mediated immunity. “The T-cell immunity impairment as well as the tumor progression enhancement emphasize the importance of the therapeutic management of stress to improve the prognosis of cancer patients.”8 Aside from demonstrating the role of stress in tumor growth, this study highlights the value of behavioral health programming to guard against these effects. Managing chronic stress is the key to avoiding these stress-related anomalies that inhibit our immune response to cancer cells.
The effects of stress on ovarian cancer cells has also been evaluated. One study evaluated human ovarian cancer in mice. The mice were exposed to stress, which increased their epinephrine and norepinephrine levels. The results indicated that the presence of epinephrine and norepinephrine prevented tumor cells from dying and actually helped them grow by activating focal adhesion kinase (FAK).9 Thus, from this study, it’s clear that abnormal epinephrine and norepinephrine levels play a role in the establishment and progression of cancer, too.
The issue of sleep deprivation was also raised as a possible concern for firefighter stress, and it, too, has been shown to influence cancer. In fact, “... [a] number of studies have demonstrated that stress can disrupt neuroendocrine circadian rhythms in ways that favor tumor growth and metastasis.”10 Considering that firefighters are so routinely sleep deprived and suffering from circadian rhythm disruptions, we must consider the possibility this increases their cancer risk.
This data overwhelmingly supports the proposition that chronic stress plays a role in the development and spread of cancer. While the research on this subject matter is limited to a small number of cancers, it is reasonable to assume stress can impact additional types of cancers. With that in mind, the fire service needs to focus on stress management, both before and after a cancer diagnosis, to assist with cancer-fighting efforts and firefighter longevity.
More to do
While the fire service has taken the threat of cancer seriously, the work is not done. It is clear the fire service needs to evaluate the effects of chronic stress on cancer and to continue developing behavioral health resources for firefighters. If utilized as a routine method to build resilience, behavioral health programming may decrease the occurrence of firefighter cancer by controlling cortisol, epinephrine and norepinephrine as well as improving sleep. Additionally, if these services are used after a cancer diagnosis, they may be useful for returning and/or maintaining hormones at safe levels, which may positively impact cancer treatments.
The work the fire service has done regarding cancer prevention is crucial, but the prevention picture will remain incomplete until we recognize that there is another pervasive player in the development and spread of firefighter cancer: chronic stress.
References
1. Daniels, R. Firefighter cancer rate: The facts from NIOSH research. March 10, 2017. https://blogs.cdc.gov/niosh-science-blog/2017/05/10/ff-cancer-facts/.
2. Firefighter Cancer Support Network. Firefighter cancer fact sheet. 2017. www.firefighterclosecalls.com/wp-content/uploads/2017/06/FF-Cancer-Fact-Sheet.pdf
3. Wilson, JL. The Anti-Inflammatory Effects of Cortisol. Sept. 10, 2014. https://adrenalfatigue.org/the-anti-inflammatory-effects-of-cortisol/.
4. Wilson, Ibid.
5. Heid, M. How stress affects cancer risk. December 2014. www.mdanderson.org/publications/focused-on-health/how-stress-affects-cancer-risk.h21-1589046.html
6. University of Kent. Stress hormone is key factor in failure of immune system to prevent leukemia. Aug. 14, 2018. Retrieved from https://www.sciencedaily.com/releases/2018/08/180814101418.htm.
7. Bautuman, OA, et al. “Effects of repeated stress on T cell numbers and function in rats.” Brain Behav. Immun. June (1990), 105-17.
8. Frick, LR, et al. “Chronic restraint stress and the resulting presence of epinephrine impairs T-cell immunity and promotes tumor progression in mice.” Stress. March (2009), 134-43.
9. Sood, AK, et al. “Adrenergic modulation of focal adhesion kinase protects human ovarian cancer cells from anoikis.” The Journal of Clinical Investigation. 120:5 (2010), 1515-1523.
10. Moreno-Smith, M., et al. “Impact of stress on cancer metastasis.” Future Oncol. 6:12 (2010), 1863–1881.
