Sleep deprivation raises the likelihood of sleepwalking, research suggests.
Sleepwalking can be dangerous
The Université de Montréal monitored 40 suspected sleepwalkers during normal sleep, and then during rest which followed a long period of wakefulness.
The Annals of Neurology study found the number of incidents of disturbed sleep, including sleepwalking, rose sharply during "recovery" sleep.
It is estimated sleepwalking, which has been linked to aggressive and injurious behaviour, affects up to 4% people.
Sleep deprivation has been linked to sleepwalking in previous research - but the findings have been inconclusive.
The latest study focused on patients referred to a sleep disorder clinic for suspected sleepwalking between August 2003 and March 2007.
Following examination, the patients slept for a night in the lab.
The next day they went about their regular daytime activities, after which they returned to the lab in the evening, where they were constantly supervised to ensure they did not fall asleep.
Recovery sleep took place the next morning, following 25 hours of wakefulness.
All patients were videotaped during each sleep period and the researchers evaluated behavioural movements on a three-point scale of complexity, ranging from playing with the bed sheets to getting up from the bed.
During normal sleep half of the patients showed signs of disturbance, but during "recovery" sleep the figure rose to 90%.
The total number of episodes of "behavioural movement" recorded by the researchers rose from 32 in normal sleep to 92 in "recovery" sleep.
Sleep deprivation also significantly increased the proportion of sleepwalkers experiencing at least one complex episode.
Sleepwalking is thought to occur during the phases of deep sleep.
The current study found that sleep deprivation increased the problems that patients experienced in moving out of deep sleep into other phases of sleep.
Deep sleep, associated with a slow down of electrical activity in the brain, is believed to be critical to the restoration of mood and the ability to learn, think and remember.
Dr Neil Stanley, a sleep expert at Norfolk and Norwich University Hospital, said although most people thought of sleepwalking as a trivial problem, it could have serious consequences for sufferers.
He said there were instances of people suffering serious injury while sleepwalking, and of sleepwalkers committing murder.
He said: "This study shows we need to get a good night's sleep every night.
"It was thought that sleepwalking was mainly a childhood problem, which we grew out of.
"But it seems more and more adults are suffering from sleepwalking and it may be due to the fact that we are increasingly a tired, sleep deprived 24/7 society."