Timothy A. Roehrs, Ph.D., of the Sleep Disorders and Research Center at the Henry Ford Hospital in Detroit, and colleagues conducted a study involving 18 health volunteers who had an average daily sleep latency of less than 8 minutes on the multiple sleep latency test (MSLT). Participants were randomized to four nights of extended sleep (10 hours per night) or four nights of their regular bedtime. Daytime sleepiness was measured on days one and four using the MSLT, and pain sensitivity was assessed using finger withdrawal latency pain testing to a radiant heat stimulus.The researchers found that those in the extended sleep group slept an average of 1.8 hours more per night compared with those who continued their usual regular bedtime, and their average daily sleep latency increased on the MSLT. In the extended sleep group, finger withdrawal latency was also increased, indicative of a reduction in pain sensitivity. During the four experimental nights, the increase in sleep time correlated with improvement on the MSLT, which was associated with decreased sensitivity to pain.