Sleep and cancer have a complex relationship that researchers are still working to understand better. It is well known that cancer and its treatment often cause significant sleep disruptions, but it is also possible that the amount a person sleeps can change their risk of cancer.
Few diseases have as much of an impact as cancer. Although cancer death rates have been declining in the U.S., almost two million people are diagnosed with cancer every year. We cover what research has shown so far about the links between sleep and cancer, what questions remain, and what people with cancer need to know about improving their sleep.
Sleep and Cellular Health
Sleep is essential to keeping your body’s cells healthy and functioning properly. While you sleep, your body is busy performing maintenance and repair on its abundance of cells. This helps ensure that your brain, nervous system, and immune system are working normally.
One critical process that occurs during sleep is DNA repair. DNA is the essential blueprint of life, containing the vital information responsible for creating and maintaining the cells that form your body’s fundamental organs and systems.
DNA is contained inside every cell, and a cell’s DNA can frequently become damaged by things like heat, toxic exposures, and environmental radiation. Fortunately, the body is usually able to resolve DNA damage. Getting enough sleep can contribute to this process of cellular DNA repair.
Repairing damaged DNA is crucial because unwanted changes to DNA can lead to cancer. While some DNA abnormalities are inherited, most DNA damage occurs after you are born. Without DNA repair, changes to a cell’s DNA can potentially result in cancer.
Can Sleep Affect the Risk of Cancer?
While many factors are involved in the development of cancer, evidence suggests that how people sleep may affect cancer risk. Sleeping too little or too much or having other sleep problems may influence a person’s chances of getting cancer.
Both sleep and cancer are extremely complex, involving multiple systems and processes of the body. There is a great deal that remains unknown about what role sleep may play in the risk of cancer.
Sleep Quantity and Cancer
Research on how much a person sleeps and their cancer risk has shown some conflicting results. Some studies have shown an association between getting less than six hours of sleep and the risk of developing colon or stomach cancer. But other research has not found strong links between cancer and sleep deprivation.
Studies have also looked at whether sleeping a lot can impact cancer risk. Some evidence shows a correlation between sleeping longer than nine hours a night and the development of colon, liver, breast, and lung cancer.
However, scientists have not yet proven that either too much or too little sleep can directly affect the risk of cancer. If such a link exists, it may be related to the functions of the “sleep hormone” melatonin or how sleep affects the immune system and metabolism.
Sleep Quality and Cancer
Research on the relationship between sleep quality and cancer remains limited, in part because of the challenges involved in measuring sleep quality.
Sleep quality refers to how well you sleep. This includes how long it takes you to fall asleep, whether your sleep is interrupted, and the amount of time you spend in different sleep stages. Waking up frequently or feeling sleepy during the day can be signs of poor sleep quality, even after getting the recommended amount of sleep.
A limited amount of research suggests that poor sleep quality in older adults is associated with a higher long-term risk of being diagnosed with cancer. Animal studies have shown that frequently disrupted sleep can accelerate cancer growth, but the results of animal studies do not always translate to humans.
Future research may reveal more about any links between poor quality sleep and cancer risk.
Circadian Rhythm Disorders and Cancer
Disruption of circadian rhythms may put people at higher risk of developing cancer. Circadian rhythms are biological processes, such as the sleep-wake cycle, that occur during a 24-hour period.
Normal circadian rhythms are driven primarily by the timing of exposure to light and darkness, and these rhythms may be disrupted by shift work, jet lag, and disorders like delayed sleep phase syndrome.
Circadian rhythms help regulate the growth and division of cells, as well as DNA repair. This means that disrupted circadian rhythms may affect cellular function and the risk of developing cancer. Research has found connections between circadian rhythm disorders and various types of cancer, including prostate, colon, breast, pancreatic, ovarian, and lung cancers.
Obstructive Sleep Apnea and Cancer
Obstructive sleep apnea (OSA) is a disorder in which a narrow or closed airway causes repeated pauses in breathing during sleep. Some research has found an association between people with OSA, especially severe OSA, and a higher risk of cancer. Other studies, though, have observed few correlations between OSA and cancer.
OSA reduces oxygen levels during sleep, and some evidence suggests that low blood oxygen levels could be linked to the risk of cancer. But additional studies may determine more about any relationship between OSA and cancer, including whether positive airway pressure treatment might reduce the risk of cancer for people with OSA.
How Does Cancer Affect Sleep?
As many as 60% of people with cancer have trouble sleeping. Even people who never had sleep problems in the past may start having insomnia and sleep disturbances after a cancer diagnosis.
There are a number of ways cancer can negatively impact sleep.
- Pain: People with cancer may experience pain directly from how tumors affect the body or as a side effect of cancer treatments.
- Stress and anxiety: Cancer can cause understandable stress from disruption to usual routines, financial difficulties, and uncertainty and fear about the future. For people with cancer, this stress and anxiety can interfere with sleep.
- Disrupted sleep schedule: People with cancer may have their normal sleep schedule thrown off by hospital stays, drugs that make them sleepy during the day, and changes in their bowel and bladder habits that result from cancer or its treatments.
- Hormone changes: Certain types of cancers, including breast and prostate cancer, may be treated with hormone therapy that can change sleep patterns. Some tumors, called neuroendocrine tumors, may cause excess hormone production that can cause problems sleeping.
Sleep and Cancer Treatment
Drugs that are used in cancer treatment can throw off normal sleep. Some drugs, like steroids, can make people more alert and may cause anxiety and insomnia. Other drugs may make people sleepy during the day. The physical and mental side effects caused by various types of cancer treatments may also disrupt sleep.
Sleep disturbances may make it harder to stick with a treatment plan, which could affect how well treatment works. Getting enough sleep can improve quality of life and may lessen anxiety and depression during treatment. Adequate sleep also helps the body repair cell damage and allows the immune system to work better, both of which are important during cancer treatment.
Preliminary research suggests that a person’s sleep chronotype, or their body’s natural preference to sleep at certain times, may influence how they respond to chemotherapy. One study examined rates of chemotherapy side effects in people with breast cancer, and found that those with evening chronotypes reported higher instances of nausea and vomiting than morning chronotypes. However, research is inconclusive on whether timing cancer treatments based on chronotype can reduce the negative effects of chemotherapy.
Sleep and Cancer Progression
Scientists have gained new insight about how sleep could affect the way that cancer progresses. But the relationship between sleep and the progression of cancer continues to be studied.
Circulating tumor cells (CTCs) are cancer cells that enter the bloodstream, enabling cancer to spread from where it began to other parts of the body. Some breast cancer research indicates that CTCs are more active when a person is sleeping. Certain hormones that are present at higher levels during sleep may contribute to the creation and spread of these tumor cells.
It may be concerning to think that a healthy behavior like getting plenty of sleep may contribute to cancer progression. But keep in mind that, overall, sleep has many benefits for people with cancer. For example, some research found better survival rates in people with advanced cancer who slept the recommended seven or more hours per day.
Coping With Cancer and Improving Your Sleep
If cancer or cancer treatment is making it hard for you to get enough quality sleep, talk with your oncologist. The doctor who is overseeing your treatment is in the best position to determine what is causing your sleep problems and to help resolve them.
One starting point for getting better sleep is developing good sleep habits and establishing routines that are conducive to quality rest. Creating a comfortable bedroom environment, getting appropriate exercise, and avoiding foods and drinks that can disrupt sleep may help you get better rest at night.
Cancer Survivors and Sleep
Sleep issues often continue even after cancer treatment ends. But getting adequate sleep can provide many health benefits for cancer survivors, including reducing the risk of depression and cardiovascular diseases. Getting enough sleep can also enhance memory and focus, which may help with the “chemo brain” that can occur after cancer treatment.
Long-lasting sleep problems can be especially common among childhood cancer survivors. Young survivors are more likely to struggle with excessive daytime sleepiness, breathing problems during sleep, and trouble falling and staying asleep. These sleep problems can impact their behavior and overall quality of life.
Parents and caregivers of childhood cancer survivors who have ongoing sleeping problems should consult with their child’s pediatrician or oncologist and may benefit from a referral to a sleep specialist.