After analyzing previous studies, Stanford University psychiatrist David Spiegel, MD, and colleague Sandra Sephton, MD, say that sleep problems alter the balance of at least two hormones that influence cancer cells.
Sleep, Hormones, and Cancer
One is cortisol, which helps to regulate immune system activity -- including the release of certain "natural killer" cells that help the body battle cancer. Cortisol levels typically peak at dawn, after hours of sleep, and decline throughout the day.
Spiegel tells WebMD that night shift workers, who have higher rates of breast cancer than women who sleep normal hours, are more likely to have a "shifted cortisol rhythm," in which their cortisol levels peak in the afternoon. At least two studies show those women typically die earlier from breast cancer.
"We also found that people who wake up repeatedly during the night are also more likely to have abnormal cortisol patterns," he says.
Cortisol is the so-called "stress" hormone triggered, along with others, during times of anxiety and may play a role in the development and worsening of cancer and other conditions.
In addition, melatonin lowers estrogen production from the ovaries. Thus, a lack of sleep leads to too little melatonin. This series of events may expose women to high levels of estrogen and may increase the risk of breast cancer.
Spiegel says that women shift workers who are up all night produce less melatonin.
"There's a definite hormonal pattern that is affected by sleep that in itself, can predict a more rapid progression of cancer," he tells WebMD.
"Getting a good night's sleep is fairly simple, if you allow yourself to do it. The big problem for cancer patients is they take too much on themselves and don't give enough time to help their bodies cope with the illness. They're worried about burdening their families and fulfilling their usual obligations."
And that's the real message of his study, in the October issue of Brain,Behavior and Immunity. Itindicates the importance of good sleep as one of several mind-body factors that might influence cancer outcome.
Sleep, Stress, and Cancer
Previous research, including some noted in Spiegel's study, shows that cancer patients who manage their stress in group therapy, with good social networks, or with regular exercise often fare better than patients who don't manage stress effectively.
"We know that people who are depressed or anxious have a specific pattern of sleep disturbances. And if you had a bad night's sleep, you don't handle stress as well," says Spiegel. Conversely, those who better manage stress are more likely to have good sleep patterns.
Just last week, Swedish researchers said women under a lot of stress may double their risk of breast cancer compared with those who remain calm when life throws them a curveball.
"My advice for cancer patients is to try to handle stress well," says Spiegel. "By doing all the things your grandmother told you to do -- eat well, sleep well, and get plenty of exercise -- you're helping your body cope better with the disease."
Does this mean that ensuring good sleep hygiene will become the big thing in cancer treatment? No, says Len Lichtenfeld, MD, of the American Cancer Society.
"But is this important for people to remember? Yes," he tells WebMD.
"The bottom line of this report is that there is enough information to take seriously the idea that how our bodies respond to cancer is influenced by more than just the surgery, chemotherapy, or radiation. It can be influenced by stress and sleep, and these are two pieces in the puzzle that shouldn't be overlooked."