Disrupted sleep marked by poor-quality sleep and frequent awakenings can cause cancer to grow more aggressively and more quickly, suggests a new study published in the journal Cancer Research. Previous research on sleep apnea has also linked the condition, which is marked by disrupted sleep, to an increased risk of death from cancer.
To investigate the association between disrupted sleep and increased cancer incidence and mortality for the present study, researchers at the University of Chicago and the University of Louisville used a rodent model in which all the mice received the same cancer-inducing treatment. All the mice developed tumors.
After disrupting the sleep in half the mice, the researchers discovered that the immune systems of the sleep-disrupted mice were less effective at fighting the early stages of cancer than the immune systems of the well-rested mice. The tumors in the sleep-disrupted mice had grown twice as large within the same time period as the mice whose sleep was not disrupted.
In other words, disrupted sleep negatively affects the immune system. A sub-optimal immune system is less able to control or eradicate early cancers, meaning that early cancer grows faster and more aggressively. Thus, disrupted sleep can speed up the growth and development of cancer.
Explains study director David Gozal, MD, chairman of pediatrics at the University of Chicago Comer Children’s Hospital, “It’s not the tumor, it’s the immune system. Fragmented sleep changes how the immune system deals with cancer in ways that make the disease more aggressive.”
The difference in the tumor growth between the two groups of mice appears to be the result of cells from the immune system called tumor-associated macrophages (TAMs). The well-rest mice had primarily M1-type TAMs while the sleep-disrupted mice had primarily M2-type TAMs. M1 cells promote a strong immune response and can eliminate tumors cells. M2 cells suppress the immune response and instead promote the growth of new blood vessels, which encourages tumor growth.
The study, however, also discovered a potential drug therapy that could help treat early cancers: “Fortunately, our study also points to a potential drug target. Toll-like receptor 4, a biological messenger, helps control activation of the innate immune system. It appears to be a lynchpin for the cancer-promoting effects of sleep loss. The effects of fragmented sleep that we focused on were not seen in mice that lacked this protein.”
Concludes Dr. Gozal, “This study offers biological plausibility to the epidemiological associations between perturbed sleep and cancer outcomes. The take home message is to take care of your sleep quality and quantity like you take care of your bank account.”
Getting enough high-quality sleep appears important for preventing and reducing early cancer. Individuals with sleep apnea should seek treatment to decrease the risk of death from cancer.
Disrupted sleep speeds up cancer: http://www.medicalnewstoday.com/articles/271778.php
Fragmented sleep accelerates cancer growth: http://www.eurekalert.org/pub_releases/2014-01/uocm-fsa012714.php
Fragmented sleep accelerates tumor growth and progression through recruitment of tumor-associated macrophages and TLR4 signaling: http://cancerres.aacrjournals.org/content/early/2014/01/18/0008-5472.CAN-13-3014.abstract
Mother and Child Napping: http://www.freeimages.com/photo/873391