April 1, 2008, Montreal ? If you want sleepwalkers to roam around the whole night, deprive them of sleep. It may seem ironic, but a Canadian study of 40 sleepwalkers shows that when sleep-deprived, people have a greater tendency to sleepwalk.

According to University of Montreal's Dr. Antonio Zadra and his colleagues, the study supports recommendations for sleepwalkers to ?maintain a regular sleep cycle and avoid sleep deprivation.?

While sleep may seem like a steady state, it actually consists of 5 stages that cycle throughout the night. There are 5 stages of sleep including the REM (rapid eye movement) stage. A complete sleep cycle takes about 90 to 100 minutes and a regular sleep consists of 4 to 5 complete sleep cycles.

In Zadra's study, sleepwalkers spent a night at a laboratory where they were videotaped. Researchers observed their movements while they were asleep. Most sleepwalkers don't actually sleepwalk every night.

The researchers found out that many of the participants in the research had actually sleepwalked. Some of them did so more than once that night, for a total of 32 sleepwalking episodes.

On the following day, the participants were kept awake for 25 hours straight to find out how sleep deprivation would affect the sleepwalkers.

When they went to bed in the morning, they were all exhausted and were trying to get sleep at an unusual time. The researchers noted that after staying awake for 25 hours, the participants showed much different sleeping patterns compare to the night before. During their catch-up sleep period, 36 people sleepwalked for a total of 92 sleepwalking episodes.

This result brought Zadra and his colleagues to conclude that sleep deprivation may encourage sleepwalking in sleepwalkers. The findings could help in diagnosing and treating people for sleepwalking.

While this study didn't include a comparison group of people who have never sleepwalked, in the past work of Zadra's team, however, they found that healthy people with no history of sleepwalking weren't more likely to sleepwalk when sleep deprived.

This study is included in the March edition of the Annals of Neurology.