Fragmented sleep increases spontaneous pain in women

Sleep continuity disturbance impairs endogenous pain-inhibitory function and increases spontaneous pain in women.

This supports a possible pathophysiologic role of sleep disturbance in chronic pain, according to a study published in the April 1st issue of the journal SLEEP.

The study, conducted by Michael T. Smith, PhD, and colleagues at John's Hopkins University, focused on 32 healthy females, who were studied polysomnographically for seven nights. On the first two nights, the subjects slept undisturbed for eight hours. Then, the women were assigned to one of three groups: "Control", "Forced Awakening" (FA) and "Restricted Sleep Opportunity" (RSO). From nights three-to-five, the "Control" group continued to sleep undisturbed, while the "Forced Awakening" group underwent eight forced awakenings, one per hour, and the "Restricted Sleep Opportunity" group received partial sleep deprivation by delayed bedtime. On night six, both the FA and RSO groups underwent 36 hours of total sleep deprivation, followed by 11-hour recovery sleep.

In an assessment of the subjects' completion of twice-daily psychophysical assessments of mechanical pain thresholds and pain inhibition, it was discovered that the FA group demonstrated an increase in spontaneous pain, while neither the "Control" nor the RSO group showed changes in pain inhibition or spontaneous pain during partial sleep deprivation.

"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," said Smith. "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."

Recent studies associate lack of sleep with serious health problems such as an increased risk of depression, obesity, cardiovascular disease and diabetes.

Experts recommend that adults get between seven and eight hours of sleep each night to maintain good health and optimum performance.

Those who think they might have a sleep disorder are urged to discuss their problem with their primary care physician, who will issue a referral to a sleep specialist.