Sleep: A Missing Link to Cancer Prevention

Dena Ali on sleep deprivation

By Dena Ali

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The increased toxicity of the modern fireground makes cancer one of the greatest threats to firefighter health today. Although this claim has been supported by numerous studies, many of them have conflicting findings because there is no standard method to harvest data. For example, a large-scale study of 30,000 firefighters from 1960-2009 conducted by the National Institute for Occupational Safety and Health reported a nine percent increase in cancer deaths for firefighters.1 Yet, another interpretation of the same study found just a small to moderate increase for certain cancers stemming primarily from the digestive, respiratory, and urinary systems.2 Notably, this study found a two-fold increase in malignant mesothelioma from asbestos exposure. (2)



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Conclusions from these types of studies suggest the need for future research to control for such variables as gender, race, number/type of calls, and use of respiratory protection. However, studies like these have also been limited in what they tell us about techniques for cancer prevention. We’re directing efforts at limiting exposure by keeping firefighters, gear, apparatus, and stations clean. But are we missing other critical pieces of the prevention puzzle?

Effects of the Immune System

What if there was a simple way to strengthen your immune system so that your body’s natural killer cells could attack malignant (cancerous) tumor cells? There is! Humans naturally have an inbuilt system to boost these cancer-fighting cells, but to work, the system requires obtaining sufficient sleep—seven to nine hours a night. Preventing cancer by limiting exposure to toxins but failing to get proper sleep is akin to attempting to lose weight by exercise but failing to eat healthy.

In a landmark study on the impact of sleep and cancer-fighting immune cells, Dr. Michael Irwin discovered that just one night of insufficient sleep (four hours compared to eight) eliminated 70 percent of these cells circulating in the immune system.3 To further demonstrate the negative effects of insufficient sleep on the immune system, a large European study of almost 25,000 people found that sleeping six hours or less was associated with a 40-percent increased risk of developing cancer compared to those who slept seven hours or more. (3)

It’s not just the cancer-fighting cells that poor sleep renders ineffective; studies of vaccines have found that insufficient sleep can also render the body too weak to produce an effective immune response. One study found that individuals who had their sleep restricted for just a week prior to getting a flu shot produced less than 50 percent of the immune reaction compared to the group that had adequate sleep. (3)

Sleep Health

First responders are well known for their poor sleep habits, and it doesn’t take too long to hear the adage, “I’ll sleep when I’m dead” tossed around. Sadly, if that’s a motto you live by, you may have the opportunity sooner than you’d prefer. “Like water from a burst pipe in our home, the effects of sleep deprivation will seep into every nook and cranny of biology, down into your cells, and even alter your DNA.” (3) Simply put, the less time you sleep, the less time you will live. In his research, sleep scientist Dr. Matthew Walker found that insufficient sleep was a slow form of euthanasia. Despite growing evidence for this, there is often an attitude of invulnerability in firehouses that suggests that those who need more sleep are weak or lazy. Jaqueline and Sean Toomey said it best in their article, “Addicted to Awake: Sleep Deprivation in the Fire Service,” which stated, “We are immersed in a culture that deems sleeping an indulgent, sinful activity at best.”4

Although it is easy for firefighters to attribute their sleep deprivation to their uncontrollable work schedules, many firefighters neglect sleep during their time off as well. For example, it’s common during shift change to talk about plans for the day; those plans usually surround second jobs or child care. Rarely will you hear anybody admit to needing to “go home and take a nap” because sleep’s necessity is rarely discussed in the fire service. The Toomeys argue that the first step to improving sleep in the fire service is to admit that there is in fact a problem rather than avoiding the issue and convincing each other that sleep is unnecessary.

It came as no surprise when a 2016 national study of 7,000 firefighters conducted across 66 fire departments found that 37 percent of firefighters were at risk of sleep disorders; 81 percent of that cohort had not yet been diagnosed.5 This study included educational sessions, sleep disorder screening, free treatment, and outcome measures. Despite the free treatment, only 16.3 percent of those who screened positive for the risk took advantage of it. (5) The study also found that implementing a program on sleep disorders couldsignificantly reduce the percentage of firefighters who filed an injury report. They reported that this department of 1,200 active firefighters could save approximately $2.1 million dollars annually in lost time from disability and sick hours with the implementation of a sleep health program. (5)

However, if firefighters who screened positive for risk are unwilling to pursue free treatment, how can we expect all members to proactively be screened for risk? The only way is through exposing the damaging effects of poor sleep by educating members on their biological need for sleep. Agency leaders must invest in their members by placing priority on exposing the dangers of inadequate sleep.

The fire service must normalize the need for sleep in the same way it has normalized the use of self- contained breathing apparatus. This starts by recognizing that the leading causes of the diseases that are crippling health care systems and the fire service such as heart disease, obesity, depression, suicide, diabetes, and cancer have causal links to poor sleep.

In shift workers, increased incidences of cardiovascular disorders, peptic ulcers, and reproductive dysfunction are well known, and all are attributed to sleep disorders.6 Shift work is strongly linked with cancer and is now classified as a “probable carcinogen” by the World Health Organization. (6) Sadly, although sleep disorders are common, costly, and treatable, many remain undiagnosed and untreated. (6)

In 2013, the American Medical Association issued a warning report that attributed certain cancers, obesity, diabetes, and psychiatric disorders with disruption of circadian rhythmicity to use of electric light at night.7 Electric light emitted from phones, televisions, and interior lights effectively suppresses melatonin and leads to circadian confusion. Working frequent extended shifts and long workweeks leads to sleep deficiency and misalignment of circadian phase.

In addition to metabolic disorders, poor sleep contributes to all major psychiatric conditions including depression, post-traumatic stress disorder (PTSD), anxiety, and suicide. Abnormalities of rapid eye movement sleep are considered specific to major depressive disorder (MDD) and connect shift work with depression. (6) Compared to all disorders associated with suicide, MDD confers the greatest risk.8 Although lifetime rates of major depressive disorder are 17 percent, the suicide rate among people with MDD is 20 times higher than a person without it. When compared to people who sleep for six to eight hours a day, the suicide rate is 3.5 times higher in those who sleep fewer than four hours a day. (6)

Connection to Cancer

However, of all the illnesses associated with poor sleep, learning about its connection to cancer was the most frightening. Epidemiological studies on shift work discovered that sleep disruption increases your odds of developing numerous forms of cancer, including breast cancer, prostate cancer, and colon cancer. (3) In fact, because of the increased evidence connecting sleep disruption with cancer, Denmark became the first country to pay workers’ compensation to a woman who had developed breast cancer after years of night shift work. A recent European study of almost 25,000 people found that sleeping fewer than six hours was associated with a 40 percent increased risk of developing cancer compared to those sleeping for seven hours or more. (3)

The connection between insufficient sleep and cancer has to do with sleep’s connection to the inflammatory response. Lack of sleep forces the sympathetic nervous system into overdrive and thereby causes an inflammatory response from the immune system. In the short term, inflammation is necessary to help your body fight disease; however, it increases the risk for several chronic diseases. The longer sleep insufficiency lasts, the longer your body remains in some degree of the fight-or-flight state. This can last for years with those who have untreated sleep disorders or excessive work hours or who simply choose to neglect their sleep.


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According to Dr. Walker, “Like a car engine that is revved to a shrieking extreme for sustained periods of time, your sympathetic nervous system is floored into perpetual overdrive by lack of sleep. The consequential strain that is placed on your body by the persistent force of this sympathetic activation will leak out in all manner of health issues, just like the failed pistons, gaskets, seals, and gnashing gears of an abused car engine.” (3)

Cancers use the inflammatory response to their advantage by luring inflammatory factors into the tumor mass to initiate the growth of blood vessels that feed it with more oxygen and nutrients. Tumors use the inflammatory response to help further damage and mutate the DNA of their cells, increasing the tumor’s strength. (3) Because of this, lack of sleep is causally associated with metastasis, allowing the cancer to spread to other parts of the body. Once cancer metastasizes, intervention becomes more complicated, and death rates increase. However, if metastasis can be delayed, localized cancers are more easily eradicated.

This metastatic relationship was studied at the University of Chicago by Dr. David Gozal, who injected mice with malignant cells and tracked tumor progression. In the study, half the mice were allowed to sleep normally while the other half had their sleep partially disrupted to reduce their sleep quality. As a result, the sleep-deprived mice experienced a 200-percent increase in the speed and size of cancer growth compared to the rested group.

Postmortem studies of the mice found that the tumors were far more aggressive in the sleep- deficient animals. Their cancer had metastasized by spreading to surrounding organs, tissues, and bones. Gozal’s work in the years after this experiment found that immune cells are the root cause of the cancerous influence resulting from sleep loss. Sleep loss diminishes the ability of immune cells to combat cancer while supporting the cancer growth alternative cells, M2 cells. (3) With this discovery, Gozal realized that poor sleep increases the risk of cancer development and, if cancer is established, provides a healthy environment for its rapid and more rampant growth. (3) Walker likens not getting sufficient sleep when fighting cancer to pouring gasoline on an already aggressive fire. (3)

If we are serious about preventing cancer among first responders, we must prioritize changing the way we view sleep. Agency leadership must also prioritize finding ways to increase the quality of sleep among its members by encouraging them to be evaluated for sleep disorders; this evaluation should include educational sessions that will encourage better sleep hygiene practices and treatment.

Sleep Education and Stages

Our indifference toward sleep is directly related to our historic failure to explain and understand sleep’s purpose. Today, science has advanced sufficiently to the point where we understand that sleep is the single most effective thing we can do to reset our brain and body health each day. (3) Sleep serves our brains by enriching our ability to learn, memorize, make decisions, and process events. In fact, dreaming has been found to serve as virtual reality space that mollifies painful memories. In essence, dreaming is built-in therapy necessary for trauma processing and the prevention of PTSD.

Sleep further serves to recalibrate the body by releasing toxic waste and anabolic hormones, tissue repair, and a process of resetting nerve cells in the brain, all of which assist with regulating our blood pressure, sugar levels, and immune system. Without necessary sleep, hormone levels alter drastically. Among first responders with poor sleep, testosterone and cortisol levels have commonly been found to be dangerously out of range.

Through advances in science and technology, we now understand that our bodies are designed to experience four stages of sleep each night. These stages progress through approximately four or five 90-minute cycles that rotate between a nonrapid eye movement (NREM) state and a rapid eye movement (REM) state. The first two cycles are primarily dominated by NREM deep sleep, while the last two cycles consist primary of REM sleep. Both stages of sleep serve different roles for the body and mind. NREM is necessary for mental and physical recovery, while REM is necessary for cognition and processing of memories.

If you naturally sleep an average of seven to nine hours a night, you are more than likely allowing your body to complete the four necessary stages of sleep. People who stay up too late rob their bodies of NREM sleep; those who wake up early rob their bodies of REM sleep.

Those who suffer from sleep disorders such as sleep apnea and insomnia are deficient in these stages and thereby suffer from chronic sleep deprivation. This condition results in fatigue that manifests itself in many mental and physical ailments.

Walker recommends a few simple ways to evaluate if you are getting sufficient sleep. Number one is if you didn’t set an alarm clock, would you sleep past that time? If so, your body needs more sleep than what you are allowing it, and you should consider an earlier bedtime. Also, during the day, do you find yourself rereading the same sentence multiple times (fatigued brain)? Finally, do you sometimes forget what color the last few traffic lights were (distraction)?

If you regularly sleep seven to nine hours and still experience these symptoms, you should consider being evaluated for a sleep disorder that may be interrupting your sleep. If you experience these symptoms because you don’t sleep sufficiently, consider finding ways to get more sleep. Additionally, if you are using sleeping pills or alcohol as a sleep aid, understand that these substances work as a sedative and inhibit true restorative sleep. They inhibit the REM stage of sleep, which prevents the brain’s natural ability to recalibrate, regulate emotions, and process memories. The use of alcohol and sleeping pills has been found to contribute to early mortality, emotional dysregulation, and PTSD.

Individuals and company- and agency-level members can take many actions to improve their sleep. At the individual level, work on consistent bedtimes and rid sleeping areas of any distractions. When your body recognizes you are in bed solely to sleep, you fall asleep easier. Other suggestions include the following:

  • Limit the use of electronic devices in the hour before going to bed.
  • Drop your body temperature by two degrees, which allows you to fall asleep easier. Find ways to reduce the temperature in your bedroom.
  • Exercise daily, which motivates the body to sleep better. However, try not to exercise within three hours of sleep.
  • Stop using the “snooze” button on your clock. If you snooze for 30 minutes, you have robbed your body of approximately 25 percent of REM sleep. (REM sleepdominates the end of the last two sleep cycles.)
  • If you toss and turn, unable to calm your mind while attempting to sleep, there are ways to calm your mind. First, hide any time-keeping devices to reduce stress. Practice mindfulness by doing a simple breathing exercise. One of the simplest is the Navy SEALs’ breathing technique where you inhale for four seconds, hold your breath for four seconds, exhale for four seconds, and hold your breath for four seconds. By focusing on your breath, you start to calm the mind. This technique also reduces your respiratory rate and activates the parasympathetic nervous system. Using the sleep stories included in the calm and head- space apps are extremely helpful.
  • If you are still unable to fall asleep, get out of bed and go to another room. Keep the light dim and engage in a calming activity (not television).
  • Take naps! Dr. Allison Brager, sleep scientist for the Department of Defense, recommends napping for 20 to 30 minutes. A trick she has shared includes consuming a dose of caffeine right before lying down for a nap. Because caffeine takes 30 minutes to kick in, you should immediately feel its effects when you wake up. Take a 90-minute nap after lunch or in the early evening. If you work on a busy company and may be up most of the night, doing this allows you to complete one full cycle of sleep, thereby becoming more alert during the overnight hours.
  • Limit taking over-the-counter sleeping pills.
  • Eliminate alcohol within four hours of bedtime.
  • Establish a consistent nighttime routine that is free of light and low in mental and physical intensity.
  • Eliminate caffeine intake after lunchtime. Caffeine has an average half-life of five to seven hours. This means if you have a cup of coffee with the crew at 7 p.m., you may still have half the caffeine in your system at 1 a.m.
  • Encourage members to practice sleep hygiene techniques. One of the greatest things a company officer can do for his crew is recognize the need for sleep and
  • encourage his members to change their habits, including nap taking, quiet dorms, and being awakened only for your company’s response.
  • Eliminate telephone use, television watching, and other electronic devices in dorm areas. When your body recognizes an area is only for sleep, it is able to fall asleep more quickly.
  • Keep dorm temperatures approximately 2°F to 3°F cooler than other areas of the firehouse.
  • Sleep in private dorms that are free of distractions and the sound of snoring.
  • Use dim lighting in the dorm.
  • Replace trip lights with a calmer red light.
  • In multicompany stations, awaken only the crew being dispatched for a call.
  • Focus on finding a schedule that allows more recovery time after shifts. The current 56-hour work- week is not optimal. One study found that one to two nights of recovery sleep are required to recuperate from deficits caused by a 24-hour shift.
  • If you suffer from insomnia, search for a therapist trained in cognitive behavior therapy for insomnia.
  • If you rarely feel refreshed after sleeping, be evaluated for a sleep disorder.
  • Tart cherry juice is a natural sleep aid and an anti-inflammatory. You can purchase concentrated versions at your local grocery store.
  • For more tips, go to

Firefighters are at increased risk for cancer and many other metabolic and psychological disorders. Each of these has been found to be causally connected with insufficient sleep. Firefighters are notorious for their disrupted sleep and indifference to- ward the need for sleep. Now that we have learned that sleep is a biological necessity and its absence is a slow form of euthanasia, we must change the way we view the need for sleep.

Firefighters must be encouraged to place priority on their sleep, and their employers must become educated in methods to encourage sleep hygiene techniques while reducing the number of interruptions their members experience when not responding to emergencies.

Finally, for the fire service to understand the true culprit behind cancer and also make strides at prevention, we must place emphasis on controlling not only demograph- ics and exposures but also personal health factors to include sleep and nutrition.


1, NIOSH Science Blog (May 18, 2018). Retrieved from

2. Daniels RD, Kubale TL, Yiin JH, et al. (2013). “Mortality and cancer incidence in a pooled cohort of US firefighters from San Francisco, Chicago and Philadelphia (1950–2009).” Occupational and Environmental Medicine, 71(6), 388-397. doi:10.1136/oemed-2013-101662.

3. Walker MP (2018). Why we sleep: Unlocking the power of sleep and dreams. New York, NY: Scribner, an imprint of Simon & Schuster.

4. Toomey S and J Toomey (2018, November 15). “Addicted to Awake: Sleep Deprivation in the Fire Service.” Retrieved from awake.html

5. Sullivan J, O’Brien C, Barger L, et al. (2017). “Randomized, Prospective Study of the Impact of a Sleep Health Program on Firefighter Injury and Disability.” Sleep, 40(1), 1-10. doi:10.1093/sleep/ zsw001.

6. Emet M, Uzkeser M, Guclu S, et al. (2016). “Sleep Disorders in Shift Workers in the Emergency Department and Efficacy of Melatonin.” Eurasian Journal of Emergency Medicine, 15(1): 48-53. doi:10.5152/eajem.2016.84758.

7. Hatori M, Gronfier C, Gelder RN, Bernstein, PS, Carreras, J, Panda, S, . . . Tsubota, K. (2017). “Global rise of potential health hazards caused by blue light-induced circadian disruption in modern aging societies.” Aging and Mechanisms of Disease, 3(1). doi:10.1038/s41514-017-0010-2.

8. Joiner TE, Witte T, Rudd MD, et al. (2009). The interpersonal theory of suicide: guidance for working with suicidal clients. Washington: American Psychological Association.

As originally seen in the 2019 Fire Engineering Wellness supplement.

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