Fragmented Sleep Linked to Increased Cancer Risk

First Posted: Jan 27, 2014 11:56 AM EST

To date, the U.S. Centers for Disease Control and Prevention (CDC) estimates that close to 70 million Americans suffer from chronic sleep issues.

Besides working with these issues to get through the day, a recent study shows that sleep marked by frequent awakenings may increase the risk of cancer growth, tumor aggressiveness and even dampen the immune system's ability to eradicate early detection of cancerous lesions.

"It's not the tumor, it's the immune system," said study director David Gozal, MD, chairman of pediatrics at the University of Chicago Comer Children's Hospital, via a press release. "Fragmented sleep changes how the immune system deals with cancer in ways that make the disease more aggressive."

"Fortunately, our study also points to a potential drug target," he added, via the release. "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."

For the study, researchers studied mice that were housed in small groups. During the day as the mice normally slept, a quiet, motorized brush moved through half of the cages every two minutes that forced them to wake up and then go back to sleep. The rest of the mice involved in the study were not disturbed.

Following seven days in this setting, both groups were injected with cells from one of two tumor types (TC01 or 3LLC). All of the mice developed palpable tumros within 9 to 12 days and were evaluated four weeks after inoculation.

Researchers found that tumors from the mice with fragmented sleep were twice as large than for those who slept normally. A follow-up experiment also revealed that when tumor cells were implanted in the thigh muscle, these tumors became more aggressive in those with disrupted sleep patterns.

"In that setting, tumors are usually encased by a capsule of surrounding tissue, like a scar," Gozal said, via the release. "They form little spheres, with nice demarcation between cancerous and normal tissue. But in the fragmented-sleep mice, the tumors were much more invasive. They pushed through the capsule. They went into the muscle, into the bone. It was a mess."

Researchers note that the main difference seem to be that well-rested mice primarily contained M1-type TAMs that were found concentrated in the core of the tumors, while sleep-fragmented mice had primarily M2-type TAMS that became more aggressive and abundant.

"This study offers biological plausibility to the epidemiological associations between perturbed sleep and cancer outcomes," Gozal concluded. "The take home message is to take care of your sleep quality and quantity like you take care of your bank account."

More information regarding the study can be found via the journal Cancer Research

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