How poor sleep affects cancer

A recent look into the link between sleep and health is the first study to show the direct effects of fragmented sleep on cancer growth.

According to recent research published in the journal Cancer Research, poor-quality sleep marked by frequent awakenings can speed cancer growth, increase tumor aggressiveness and dampen the immune system’s ability to control or eradicate early cancers.

“It’s not the tumor, it’s the immune system,” said study director Dr. David Gozal in a statement. “Fragmented sleep changes how the immune system deals with cancer in ways that make the disease more aggressive,” added Gozal, chairman of pediatrics at the University of Chicago Comer Children’s Hospital

Dr. Gozal and colleagues studied two groups of mice, one that slept normally and one that had its sleep frequently disturbed for the purposes of the experiment. The researchers found that tumors from mice with fragmented sleep were twice as large and much more aggressive in their invasion of surrounding tissue.

“In the fragmented-sleep mice, the tumors were much more invasive,” said Dr. Gozal. “They went into the muscle, into the bone. It was a mess.”

However, the study also found a possible method for triggering the immune system to fight these effects of fragmented sleep. A biological messenger called toll-like receptor 4, or TLR4, helps control activation of the immune system. In mice lacking TLR4, tumor growth was no greater than in mice with undisturbed sleep, offering insight into potential methods for limiting the effects of sleep on cancer growth.

The Centers for Disease Control and Prevention estimate that 70 million Americans suffer from chronic sleep problems. “Considering the high prevalence of both sleep disorders and cancer in middle age or older populations,” the study authors wrote, “there are far-reaching implications.”

“The take-home message,” said Dr. Gozal, “is to take care of your sleep quality and quantity like you take care of your bank account.”