By Pat Anson, Editor

Getting a good night’s sleep plays a key role in determining how bad your pain levels are doing the day, according to a large new study by researchers in Norway.

The study included more than 10,400 adults from an ongoing Norwegian health study. Each participant underwent a standard test of pain sensitivity -- the cold pressor test -- in which they were asked to keep their hand submerged in a cold water bath for 106 seconds.

Only 32% of participants were able to keep their hand in cold water throughout the experiment. Those who suffered from insomnia were more likely to take their hand out early: 42% did so, compared with 31% of those without insomnia.

Pain sensitivity also increased depending on the frequency of insomnia. Those who had trouble sleeping at least once a week had a 52% lower pain tolerance, while those who reported insomnia once a month had a 24% lower tolerance for pain.

"While there is clearly a strong relationship between pain and sleep, such that insomnia increases both the likelihood and severity of clinical pain. It is not clear exactly why this is the case," wrote lead author Børge Sivertsen, PhD, of the Norwegian Institute of Public Health.

The study, which is published in the journal PAIN,  is the first to link insomnia and impaired sleep to reduced pain tolerance in a large, general population sample. The results suggest that psychological factors may contribute to the relationship between sleep problems and pain, but they do not fully explain it.

“We conclude that impaired sleep significantly increases the risk for reduced pain tolerance. As comorbid sleep problems and pain have been linked to elevated disability, the need to improve sleep among chronic pain patients, and vice versa, should be an important agenda for future research,” the study said.

A previous study in Norway found that women who have trouble sleeping are at greater risk of developing fibromyalgia – although it’s not clear if there’s a cause and effect relationship between the two symptoms.

Another study, recently published in PLoS One, found that insomnia – not surprisingly – made chronic pain patients less likely to exercise. Researchers followed 119 chronic pain patients, most of whom suffered low back pain, and found that quality of sleep was the best predictor of physical activity the next day – not mood or pain intensity.