Sleepless nights may encourage pain

Poor sleep can raise risks for pain in women, a new study suggests.

"This study finds that fragmented sleep profiles, akin to individuals suffering from middle of the night insomnia, health care workers on call, and parents caring for infants, alter natural systems that regulate and control pain, and can lead to spontaneous painful symptoms," researcher Michael T. Smith, of Johns Hopkins University, said in a prepared statement.

The findings are published in the journal Sleep.

The study included 32 healthy women who were studied for seven nights. For the first two nights, the women slept undisturbed for eight hours. For the next few nights, the women were then assigned to one of three groups: a control group that continued to sleep undisturbed; a forced awakening (FA) group awakened once an hour (eight times) through the night; and a restricted sleep opportunity (RSO) group subjected to partial sleep deprivation by delaying their bedtime.

On the sixth night, the women in both the FA and RSO groups underwent 36 hours of total sleep deprivation, followed by an 11-hour recovery sleep.

During the study, researchers tested the women's pain thresholds and pain inhibition. The women in the FA group showed an increase in spontaneous pain, while those in the control and RSO groups showed no changes in spontaneous pain or pain inhibition.

"Our research shows that disrupted sleep, marked by multiple prolonged awakenings, impairs natural pain control mechanisms that are thought to play a key role in the development, maintenance, and exacerbation of chronic pain," Smith said.