Troubled Sleepers Face Increased Risk of Cancer

The millions of Americans who struggle to get a good night’s sleep have a new worry to add to their tossing and turning: researchers have found surprising links between lack of sleep and several types of cancer, including prostate, breast, and colon cancer, among others.

Sleep disorders are a widespread problem, affecting 50 to 70 million Americans, according to the Centers for Disease Control (CDC). Sleep insufficiency is also linked to reduced quality of life and increased mortality.

Arm yourself with knowledge—and the good practices that can help you get a full night’s sleep—to limit your chances of developing illness down the road.

Restless nights spell trouble for men’s health

Men who reported trouble sleeping were up to twice as likely to develop prostate cancer as those who slept well, according to a new paper published in the journal, Cancer, Epidemiology, Biomarkers & Prevention. This association was even stronger in cases of advanced prostate cancer, and the risk increased relative to the severity of the sleep problems.

The study, which took place at the University of Iceland, followed more than 2,100 older men, among whom 8.7% and 5.7% reported “severe” or “very severe” sleep problems, respectively. None of the participants had prostate cancer at the start of the study, but 6.4% developed the disease within five years. Troubled sleepers, including those with problems falling asleep or staying asleep, were far more likely to develop prostate cancer.

The lead researcher, Lara Sigurdardottir, Ph.D., expects that, “If our results are confirmed in future studies, sleep may become a potential target for intervention to reduce the risk of prostate cancer.”

Fortunately, rates of diagnosis and death from prostate cancer have been declining in the United States since the 1990s. However, the disease remains a leading health concern—and the second most common cause of cancer deaths—among American men.

Lack of sleep has been linked to other forms of cancer, as well. Sigurdardottir notes that, “Most observational studies to date on circadian disruption and cancer have investigated the association between shift work and cancer risk. Among men, there are indications for increased risk of some cancers among night shift workers, such as prostate cancer, colorectal cancer, and non-Hodgkin's lymphoma.”

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Inadequate slumber puts women at risk too

Sleepless men aren’t the only ones facing greater danger from cancer. Too little sleep may also contribute to the recurrence of breast cancer among women, according to a recent study published in Breast Cancer Research and Treatment.

The researchers surveyed 412 women diagnosed with pre-menopausal breast cancer about their average length of sleep each night. Their analysis of participants’ responses and medical records uncovered a link between duration of slumber and cancer recurrence, as well as aggressive tumors. Women who slept an average of six hours or less each night were more susceptible to cancer recurrence than women who caught more z’s.

The researchers speculate that efforts to increase duration and improve quality of sleep could reduce women’s risk of developing more aggressive and recurrent breast cancers.

Too little shuteye increases risk of colon cancer

Another recent study from Case Western Reserve University School of Medicine found that people who snooze for less than six hours each night are at 50% greater risk of developing colorectal adenomas than those who sleep for seven hours or more. Colorectal adenomas—a common form of polyp—can develop into cancer tumors if left untreated.

Participants in the study were asked to complete a survey by phone before attending a colonoscopy. Even after adjusting for other risk factors, including family history, waist-to-hip ratio (a measure of obesity), and smoking, there was a clear link between sleep deprivation and adenomas.

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Melatonin production, insulin resistance, and obesity may play a role

No one knows for sure why lack of sleep is linked to cancer. However, in an interview with Science Daily, Li Li, M.D., a family physician and Associate Professor of Family Medicine, Epidemiology and Biostatistics at Case Western Reserve University School of Medicine, theorized that, “less sleep may mean less production of melatonin, a natural hormone that in animals has been linked to DNA repair.” In animal studies among mice and rats, melatonin has been shown to prevent and delay cancer growth.

Li also suggests that, “insulin resistance may underlie the link between sleep disturbance and cancer development.” This hypothesis is supported by previous research findings, which have identified potential links between chronic sleep loss, insulin resistance, obesity, and cancer.

So sleep well!

Reduce your risk of cancer and other life-threatening illnesses by getting enough sleep at night. If you find yourself tossing and turning, or waking up tired each morning, follow these simple steps to get the rest you need:

  • Eat a healthy diet. People who eat a wide variety of foods experience the healthiest sleep patterns. Slumber-friendly nutrients include Vitamin C, found in fruits and vegetables; selenium, found in nuts, meat, and shellfish; and lycopene, found in tomatoes, watermelons, and other red- and orange-coloured foods.
  • Spend some time in the sun. Bright light is known to moderate the body’s internal clock and reset sleep cycles. Soak in as much morning light as possible, by going for a walk or enjoying breakfast by a sunny window. When evening arrives, dim the lights and turn off glowing television and computer screens at least one hour before bedtime.
  • Cover your clock. There are few things more maddening than watching the hours tick by as you try to sleep. It’s not only frustrating, but also counterproductive: “clock-monitors” report more pre-sleep worry and take longer to conk out.
  • Stick to a regular schedule. Saturday morning sleep-ins are hard to resist—but keeping a regular schedule helps to maintain your body’s internal clock, while contributing to healthier and restorative sleep patterns. Wake up at the same time each morning, and delay your weekend rising no more than 60 minutes.

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