In the study published in the journal SLEEP, researchers tested 18 healthy, pain-free, sleepy volunteers.
The participants were randomly assigned to four nights of either maintaining their habitual sleep time or extending their sleep time by spending 10 hours in bed per night.
Objective daytime sleepiness was measured using the multiple sleep latency test (MSLT), and pain sensitivity was assessed using a radiant heat stimulus.
Results showed that the extended sleep group slept 1.8 hours more per night than the habitual sleep group. This nightly increase in sleep time during the four experimental nights was correlated with increased daytime alertness, which was associated with less pain sensitivity.
In the extended sleep group, the length of time before participants removed their finger from a radiant heat source increased by 25 per cent, reflecting a reduction in pain sensitivity.
The authors report that the magnitude of this increase in finger withdrawal latency is greater than the effect found in a previous study of 60 mg of codeine.
The study combined with data from previous research, suggest that increased pain sensitivity in sleepy individuals is the result of their underlying sleepiness.
"Our results suggest the importance of adequate sleep in various chronic pain conditions or in preparation for elective surgical procedures," said Timothy Roehrs, the study's principal investigator and lead author.
"We were surprised by the magnitude of the reduction in pain sensitivity, when compared to the reduction produced by taking codeine," Roehrs said in a American Academy of Sleep Medicine statement.
According to the authors, this is the first study to show that extended sleep in mildly, chronically sleep deprived volunteers reduces their pain sensitivity.
