Although clinical reports have suggested that sleep deprivation can lead to sleepwalking in predisposed patients, small studies using this method in the laboratory have yielded mixed results. A new, larger study found that sleep deprivation can precipitate sleepwalking in predisposed individuals and can therefore serve as a valuable tool in diagnosing this disorder. The study will be published in the Annals of Neurology, the official journal of the American Neurological Association.

Led by Antonio Zadra of the Université de Montréal, in Quebec, Canada, the study included 40 patients referred to a sleep disorder clinic for suspected sleepwalking between August 2003 and March 2007. All patients were examined and underwent one night of baseline sleep recording 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 calculated from when they had awakened the previous morning. All patients were videotaped during each sleep period and the authors evaluated behavioral movements which ranged from playing with the bed sheets to getting up from the bed, to determine if they were sleepwalking episodes. They also scored the complexity of each episode on a 3-point scale.

The results showed that while 32 behavioral episodes were recorded from 20 sleepwalkers (50%) during baseline sleep, 92 episodes were recorded from 36 patients (90%) during recovery sleep. Sleep deprivation also significantly increased the proportion of sleepwalkers experiencing at least one complex episode. “By yielding a greater number of episodes with a wider range of complexity, sleep deprivation can facilitate the video-polysomnographically-based diagnosis of somnambulism and its differentiation from other disorders,” the authors state.

Sleepwalkers are thought to suffer from an inability to sustain stable slow-wave sleep (stage 3 and 4 sleep) and the study found that these patients had increased difficulty passing from slow-wave sleep to another sleep stage or arousal following sleep deprivation, which supports this view. It is also consistent with observations that other factors that deepen sleep, such as young age or fever, may help trigger sleepwalking in predisposed individuals.

The authors caution that observing behavioral events in the sleep lab following sleep deprivation is not always sufficient to confirm a diagnosis of sleepwalking in a medical-legal context. However, they note that: “Used as a diagnostic tool, sleep deprivation shows a high sensitivity for somnambulism and may be clinically useful with a wider range of somnambulistic patients than previously reported.” They conclude that the study supports recommending that sleepwalkers maintain a regular sleep schedule and avoid sleep deprivation.

In a recent issue of the Annals of Neurology, the official journal of the American Neurological Association, authors Antonio Zadra, Mathieu Pilon and Jacques Montplaisir explain how they evaluated 40 suspected sleepwalkers. Each was referred to the Sleep Research Centre at Sacré-Coeur Hospital, a Université de Montréal teaching hospital, between August 2003 and March 2007.

“Our study found that sleep deprivation can precipitate sleepwalking in predisposed individuals,” said lead investigator Antonio Zadra. “Sleepwalkers are best to maintain a regular bedtime and avoid sleep deprivation if they wish to steer clear of somnambulism.”

One night of sleep, one night awake

Subjects who took part in the study agreed to have their baseline sleep patterns monitored during an initial all-night assessment. During a subsequent visit, patients were kept awake for the entire evening and remained under constant supervision.

Recovery sleep was allowed the next morning after patients had been awake for 25 hours. Subjects were videotaped during each sleep period as the research team evaluated their behaviour, which ranged from playing with bed sheets to trying to jump over the bed rails. Subjects were evaluated on a three-point scale based on the complexity of their actions.

Results were striking. During baseline sleep, only half of patients exhibited some 32 behavioral episodes. During recovery sleep, 90 percent of patients demonstrated a total of 92 behavioral episodes.

The study also found that sleepwalkers, previously thought to suffer from an inability to sustain slow-wave or deep sleep, had increased difficulty in passing from slow-wave sleep to another sleep stage or to be fully awake following sleep deprivation. “This research also reveals that objective methods can now be used for investigating and diagnosing sleepwalking,” said Dr. Zadra.