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The researchers noticed that tumors in mice whose sleep was gently interrupted every two minutes grew faster and were more invasive than tumors in mice that were allowed to sleep fully and deeply. The scientists also noticed that in the sleep-disturbed mice, cells that would normally fight off cancer became permissive to the disease. Even they secreted chemicals that allowed the cancers to grow faster and become more invasive to surrounding tissues.
"In principle, these [findings] should be applicable to human solid tumors in general," says the study's lead author, David Gozal, MD, physician-in-chief at Comer Children's Hospital at The University of Chicago, adding that, of course, studies in human cancer cells are needed to confirm his findings. He also found that the changes weren't specific to any one type of tumor, so theoretically, interrupted sleep could trigger the growth of any cancer.
"Cancers usually take on a life of their own after they overcome the natural defense systems in our bodies," Dr. Gozal says. So what his study points to, he says, "is the importance of regular healthy and high-quality sleep habits in anyone." Cancer patients in particular need rest because of sleep's ability to "harness the power of our innate immune systems to fight against the cancer."
Fragmented sleep has long been associated with an increased risk of early death, heart disease, and stroke, and it affects more people than those with sleep apnea. It's also a symptom of disorders including restless-leg syndrome, chronic pain, psychiatric problems, and even digestive ailments like irritable bowel syndrome.
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So it's important to address any sleep problems you're having with your doctor. Here are a few signs you might be suffering from fragmented sleep, according to the Cleveland Clinic:
• Lack of dreaming, caused by not getting enough REM sleep
• Morning headaches, which are triggered by high blood pressure that could be caused by sleep apnea or an inability to breathe while sleeping
• Excessive daytime sleepiness (to assess whether your sleepiness is excessive or normal, find out how it rates on the Epworth Sleepiness Scale)
• Difficulty concentrating
• Memory loss
• Depression, both the clinical disorder and a general grumpy mood caused by poor sleep
• Impotence—yes, sleeping with your significant other is a lot harder when you don't get enough sleep!