Extended sleep takes the pain out of mild chronic sleep loss

By Lucy Piper, Senior medwireNews Reporter

Increased sleep time and reduced sleepiness in mildly sleepy, but otherwise healthy, individuals increases alertness and in turn reduces pain sensitivity, US researchers have found.

"Our results suggest the importance of adequate sleep in various chronic pain conditions or in preparation for elective surgical procedures," says Timothy Roehrs (Henry Ford Hospital, Detroit, Michigan) in a press statement.

"We were surprised by the magnitude of the reduction in pain sensitivity, when compared to the reduction produced by taking codeine."

The 18 study participants did not have unusually short bedtimes, at an average of 7.4 to 7.8 hours per night, but they were excessively sleepy, with an average daily sleep latency on the Multiple Sleep Latency Test (MSLT) of less than 8 minutes, despite having an unusually high sleep efficiency, at 94%.

Half of the participants were randomly assigned to undergo 4 nights of extended bedtime (10 hours) and these individuals ended up sleeping 1.8 hours more per night than the remaining participants who continued with their habitual bedtimes.

Average daily sleep latency increased over the 4 days in individuals in the extended bedtime group, from an average 4.5 minutes to 9.6 minutes by day 4, but not in those continuing with their normal bedtimes.

The benefits of increased sleep time and reduced sleepiness were associated with reduced sensitivity to pain, the researchers note.

The length of time it took patients in the extended sleep group to withdraw their finger from a radiant heat source increased by 25%, whereas there was no increase in the habitual bedtime group.

The magnitude of this increase in finger withdrawal latency, as a reflection of reduced pain sensitivity, compares with findings from a previous study of codeine 60 mg versus placebo, in which the painkiller increased finger withdrawal latency by 14% in nonsleepy healthy individuals, but had no effect in sleepy individuals.

"The current results suggest that the increased pain sensitivity of the sleepy individuals is the result of their underlying sleepiness, which the results of this study show is a state and not a trait phenomenon," the team explains in SLEEP.

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