Scientists have long known that people afflicted with chronic pain conditions also tend to suffer from poor or interrupted sleep. The experts assumed that the pain prevented these patients from getting a good night's rest.
But a new study suggests that fragmented sleep, by itself, could make some healthy people more sensitive to pain.
For the sleep-lab study, the researchers recruited 32 healthy young women. The female volunteers were divided into three groups: One group was repeatedly awakened at set times throughout the nights of the study. Another went to bed late and got up early for a total of four hours a night of uninterrupted sleep. And a third group got a full eight hours of uninterrupted sleep.
After three nights of such tests, the women who were subjected to the incessant sleep disruptions showed a significant change in their reaction to pain. They reported more aches and pains following the nights of broken sleep. And they seemed less able to suppress pain when they underwent a series of pain tests.
The women in the other two sleep groups did not experience such a change in reaction to pain.
"This new study shows that sleep fragmentation, not necessarily the amount of sleep loss, impairs the brain's natural pain inhibitory mechanisms," said the lead researcher, Michael Smith at John's Hopkins University in Baltimore.
At the very least, the findings indicate that impaired sleep could worsen the plight of people with chronic pain disorders such as fibromyalgia or arthritis.
However, it also suggests "sleep disturbances could directly contribute to the development of chronic pain disorders," Dr. Smith said.
That means his study, published in the journal Sleep, could have big implications because large numbers of people go through periods when their sleep is routinely interrupted.
Dr. Smith says people with sleep problems should seek medical help.
"The good news is that most sleep disorders can be effectively treated with behaviour therapy, or medication or medical/dental devices, depending on the problem."