Disrupted sleep speeds up cancer
It’s well known that having a good night’s sleep is essential for maintaining proper health. And now a study funded by the National Institutes of Health shows, for the first time, a direct correlation between disrupted sleep and cancerous tumor growth in animals.
Published in Cancer Research, the study — conducted by researchers from the Universities of Chicago and Louisville — found that mice that did not sleep through the night developed bigger, more aggressive tumors than mice that slept soundly.
During a series of experiments, researchers swept the outside of cage bars of one group of mice to wake them from their slumber before returning to sleep, whereas the other group remained undisturbed. A week later, the mice received tumor cell injections to sprout tumors.
The mice that didn’t sleep well had tumors twice the size of the well-rested mice. An additional experiment revealed tumors in the thighs of ill-rested mice were more aggressive, invading surrounding tissue.
Why? The researchers explained that a lack of sleep affects the immune system and, therefore, the body’s ability to fight off disease. Crucial immune cells called tumor-associated macrophages (TAMs) help fight cancer, or can provide the tumor with new avenues for growth via blood vessels. In well-rested mice, TAMs worked inside the tumor to eliminate cancerous cells. However, in the mice with fragmented sleep, the TAMs worked on the edges of the tumor and ended up promoting blood vessel growth to allow the cancer to expand and spread.
The researchers also found a biological messenger that triggers the immune system: the protein TLR4. Mice that lacked this protein weren’t affected by disrupted sleep, nor did their tumors grow faster. It’s believed this marker provides a biological explanation for the relationship between disrupted sleep and cancer growth.