A Good Night’s Sleep is More Important than You Think
Not getting enough sleep at night is more than just a “beauty” issue. Chronic insomnia and poor quality sleep is damaging to your health. A new study links fragmented sleep with an increased risk of aggressive cancer.
Study director David Gozal MD, chairman of pediatrics at the University of Chicago Comer Children’s hospital, and a team of researchers devised a series of experience in laboratory mice to evaluate the damaging effects of disrupted sleep. The study group of mice were housed in small groups and frequently interrupted from sleeping. A control group of mice were not disturbed. After seven days, both groups of mice were injected with cells from one of two tumor types (TC-1 or 3LLC). All mice developed cancer within 9 to 12 days.
The mice with fragmented, poor quality sleep had tumors that were twice as large for both tumor types as those who had slept normally. The cancers were also more aggressive and invaded surrounding tissue in the mice with disrupted sleep.
Dr. Gozal says that the immune system is to blame. “Fragmented sleep changes how the immune system deals with cancer in ways that make the disease more aggressive," he notes. Tumor-associated macrophages (TAMs) cluster at the sites of tumors. These are a hallmark of the immune system’s response to cancer, but they can respond in a variety of ways, depending upon the chemical signals they receive.
Well-rested mice had primarily M1-type TAMs, which promote a strong immune response and can eliminate tumor cells. Those with poor quality sleep produced M2-type TAMs, which encourages tumor growth.
"Fortunately, our study also points to a potential drug target,” said Dr. Gozal. "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."
Taking TLR4 out of the picture resulted in major curtailment of tumor growth. "When we injected tumor cells into mice that lacked TLR4," Gozal said, "the differences between undisturbed and sleep-fragmented mice disappeared."
The Centers for Disease Control and Prevention estimate that about 50-70 million Americans suffer from chronic sleep problems. In addition to biological changes, poor sleep habits can affect mood, learning, memory and concentration. Inadequate rest impairs our ability to handle stress, which can lead to immune system dysfunction as well.
Regardless of its nature, any sleeping problem that lasts more than a few nights shouldn’t be ignored, advises Dr. Sandhya Kumar, assistant professor of neurology at Wake Forest Baptist Medical Center and medical director of its Sleep Center (not involved with this study).
“Even a relatively short-term difficulty with sleeping can develop into a chronic problem if not addressed, and not sleeping properly can have many other health consequences,” she said. “If you think about it, we spend about a third of our lives doing it, so sleeping is extremely important.”
F. Hakim, D. Gozal et al. Fragmented sleep accelerates tumor growth and progression through recruitment of tumor-associated macrophages and TLR4 signaling.. Cancer Research, 2014; DOI: 10.1158/0008-5472.CAN-13-3014