More sleep appears to lower pain sensitivity

A study a appearing in the December, 2012 issue of the journal SLEEP suggests that more nightly sleep in mildly sleepy, healthy adults can increase daytime alertness and, notably, reduce pain sensitivity.

“Our results suggest the importance of adequate sleep in various chronic pain conditions or in preparation for elective surgical procedures,” said Timothy Roehrs, PhD, lead investigator and author. “We were surprised by the magnitude of the reduction in pain sensitivity, when compared to the reduction produced by taking codeine.” Dr. Roehrs is the director of research at the Sleep Disorders and Research Center of Henry Ford Health System and professor in the Department of Psychiatry and Behavioral Neurosciences, School of Medicine at Wayne State University in Detroit, Michigan.

The investigators enrolled 18 healthy, pain-free, normal sleepers. They were randomized to four nights of either habitual sleep time or an extended sleep time of spending 10 hours in bed per night.

The investigators measured objective daytime sleepiness with the multiple sleep latency test (MSLT), and they measured pain sensitivity using a radiant heat stimulus.

The extended sleep group slept 1.8 hours more per night than the habitual sleepers. And increase in sleep time during the four experimental nights correlated with increased daytime alertness and less pain sensitivity.

In the extended sleep group, the mean length of time before subjects removed their finger from a radiant heat source increased by 25 percent, showing lowered pain sensitivity in the group. This increase in finger withdrawal latency was, according to the authors, greater than the effect found in a previous study of the effects of 60 mg codeine.

The authors concluded that these results, along with data from previous research, suggest that increased pain sensitivity in sleepy individuals is the result of underlying sleepiness.