Previous studies have found people with cancer who go through group therapy or have a strong social network fare better than those with weaker social support. The question has been how psychosocial factors exert their influence on cancer cells. David Spiegel, MD, the Jack, Lulu and Sam Willson Professor in the School of Medicine, and Sandra Sephton, PhD, Spiegel's former postdoctoral fellow now at the University of Louisville School of Medicine, suggest that a person's sleep/wake cycle might be the connection. Their work will be published in the October issue of Brain, Behavior, and Immunity.

"Psychosocial factors affect your behavior patterns, such as exercise, what you eat and drink, and your sleep," Spiegel said. Of these factors, how well you sleep can seriously alter the balance of hormones in your body. This makes the sleep/wake cycle, also called the circadian rhythm, a good candidate for linking a person's social network to their cancer prognosis.

Spiegel suggested two possible ways in which the circadian rhythm may influence cancer progression. The first involves a hormone called melatonin, which the brain churns out during sleep. Melatonin belongs to a class of compounds called anti-oxidants that mop up damaging free-radical compounds. With a disrupted circadian rhythm, the body produces less melatonin and the cell's DNA may be more prone to cancer-causing mutations.

Melatonin also slows the ovaries' production of estrogen. For many ovarian and breast tumors, estrogen spurs the cancerous cells to continue dividing. Shift workers who work through the night and produce less melatonin may therefore produce more cancer-activating estrogen, the researchers said
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Contact: Amy Adams
amyadams@stanford.edu
650-723-3900
Stanford University Medical Center
1-Oct-2003