Chemotherapy disrupts sleep patterns

Sleep is a chance to get away from the life-and-death struggle that cancer patients face daily, a chance to recharge and refresh. Ironically this respite may be an early casualty of chemotherapy, at least among breast cancer patients.

The sleep-wake rhythms of breast cancer patients are impaired during the administration of chemotherapy, according to a study published earlier this month in the journal Sleep. The first cycle of chemotherapy is associated with a temporary disruption of these circadian rhythms. Repeated administrations cause worse and more enduring disruptions.

"Our biological clock gets out of sync during chemotherapy, especially after the first cycle of treatment," said Sonia Ancoli-Israel, PhD, principal investigator of the study and a professor of psychiatry at the University of California, San Diego. The body tries to adapt, she said, "but with each repeated administration of chemotherapy, it becomes more difficult."

The research documents what many oncologists have noted. Between 30% and 50% of cancer patients report symptoms of insomnia, according to Ancoli-Israel. Previous studies also have shown that both sleep and fatigue get worse with chemotherapy.

The researchers don't know how chemotherapy interferes with sleep, only that it does. A good guess would involve psychological factors, such as anxiety and depression, and behavioral factors, including increased daytime napping, as well as physiological factors, such as decreased levels of estrogen, impaired cortisol responses, and inflammation. A precise understanding of the mechanism awaits further study, they said.

In the meantime, Ancoli-Israel and colleagues advise routinely screening breast cancer patients undergoing chemotherapy for sleep and circadian disruptions. Appropriate management, such as cognitive behavioral therapy or bright light therapy, may prevent sleep disturbances from becoming chronic, they said.