Lifetime Prevalence of Sleepwalking Almost 30%

Pauline Anderson

May 16, 2012

May 16, 2012 — Sleepwalking affects or has affected almost a third of Americans, and, contrary to popular opinion, hypnotic sleeping aids may not be a main culprit, a new study suggests.

Researchers found that 3.6% of a representative sample of Americans reported having episodes of nocturnal wandering (NW) with abnormal state of consciousness in the previous year. Added to those who reported having experienced such episodes in childhood, the figure increased to more than 29%.

Even this statistic probably doesn't capture the full extent of the condition because sleepwalking involves at least partial amnesia. "The numbers we present are conservative," said lead author M.M. Ohayon, MD, DSc, PhD, Stanford Sleep Epidemiology Research Center, California.

Dr. M.M. Ohayon

The prevalence related to recent episodes is surprising because it was assumed that sleepwalking was rare in adulthood, said Dr. Ohayon. To put it in perspective, he added, the prevalence of narcolepsy, another sleep-related condition, is 0.04%. "Sleepwalking is 100 times more frequent."

Their findings are published in the May 15 issue of Neurology.

Results also showed that although over-the-counter sleep aids and selective serotonin reuptake inhibitors (SSRIs) were significantly associated with sleepwalking, hypnotic sleeping pills were not. People with major depressive disorder, alcohol abuse or dependency, or obsessive-compulsive disorder were more likely to sleepwalk than those without these conditions.

This paper used the term "nocturnal wandering" instead of "sleepwalking" because diagnosis was based on subjective reports, not polysomnographic recording, which is preferred but not required for a diagnosis of sleepwalking, said Dr. Ohayon.

Representative Sample

Sleepwalking is a disorder of arousal from non-REM sleep parasomnia occurring predominantly during stages 3 and 4. It affects up to 30% of children but generally decreases with age.

The current analysis was based on a representative sample of US residents from 15 states. It involved telephone interviews with 15,929 respondents aged 18 to 102 years, more than half of whom (53.5%) were married or living with someone.

Participants were asked about the frequency and duration of NW episodes, difficulty in being aroused during an episode, mental confusion when awakened, and inappropriate behavior during sleep. They were also asked about medication use, other medical conditions, and family history of wandering at night.

The study showed that as many as 3.6% (95% confidence interval [CI], 3.3% - 3.9%) of respondents had at least 1 episode of NW in the previous year, with 0.2% (95% CI, 0.1% - 0.3%) reporting episodes at least once per week. An additional 0.8% reported having 2 to 3 episodes per month and 2.6% had 1 to 12 episodes in the previous year.

More than a quarter (25.7%) of respondents who did not report NW in the previous year reported experiencing it during childhood or adolescence, providing a lifetime prevalence of 29.2%.

The duration of NW was mostly chronic and significantly decreased with age, except for the category of 1 or more times per week.

Sleep Apnea

Having circadian rhythm sleep disorder, obstructive sleep apnea syndrome, or insomnia disorder predicted more frequent NW episodes. For example, 4.1% of those with sleep apnea had NW 2 or more times a month compared with 0.9% who didn't have this syndrome (adjusted odds ratio, 3.87).

It's interesting to note, said Dr. Ohayon, that insomnia didn't have as big an effect as sleep apnea (1.9% with this condition experiencing episodes 2 or more times per month vs 0.9% without the condition). "Insomnia is supposed to lead to a lot of disrupted sleep, but you are less harmed by insomnia than by sleep apnea" when it comes to sleepwalking, he said.

Participants with alcohol abuse or dependence (3.1% vs 0.9%), major depressive disorder (3.1% vs 0.9%), or obsessive-compulsive disorder (7.3% vs 1.0%) were significantly more likely to report NW episodes 2 or more times a month compared with those not reporting these disorders.

"We know that obsessive-compulsive disorder, major depression, and alcohol abuse provoke disruption of sleep, and all disorders that provoke sleep fragmentation or disrupted sleep are exposing the subject to risk of sleep walking," said Dr. Ohayon.

Family history played a big role, too, a finding that Dr. Ohayon found "interesting and also very surprising." Almost a third of patients with NW (30.5%) had at least 1 family member who had experienced such disorder compared with 17.2% in the rest of the sample. This number, he said, is probably underreported because not everyone knows the extent of the condition within his or her family.

Sleep Aids

Participants who took over-the-counter sleep aids (such as Benadryl, Nytol, and Tylenol-PM, which contain the antihistamine diphenhydramine) were more than twice as likely to have NW (2.5% vs 1.0% for those not taking these agents) as were those taking SSRIs (2.4% vs 0.9%). Those taking benzodiazepine and nonbenzodiazepine hypnotics were not significantly more likely to have NW compared with those not taking these sleep aids.

This finding is interesting in light of recent news stories linking hypnotic agents with accidents while "sleep driving."

"If somebody tells me that he has a history in his family of sleepwalking and he has experienced episodes himself, I would be very careful about giving him an SSRI antidepressant, and I would certainly not recommend he take an over-the-counter pill because these drugs carry the risk of having a sleep walking episode," said Dr. Ohayon.

Antidepressants may not cause the sleepwalking but could be a "trigger" in a predisposed person, he added.

The amount of sleep was another important factor. There was a higher risk of having at least 1 NW episode in the previous year in those sleeping less than 7 hours per night, after adjustment for possible confounding factors such as age and mental disorder.

Getting the Word Out

Approached for comment, Marc Raphaelson, MD, clinical director, SleepMed Inc, Washington, DC, and member of the American Academy of Neurology, said the new study helps to set the record straight about which medications might increase the risk for sleepwalking. This, he said, is especially important in light of public perceptions surrounding sleepwalking dangers linked to hypnotic sleeping pills.

"This analysis found that in patients taking nonbenzodiazepine sleeping pills…the risk of nocturnal wandering was not significantly increased," said Dr. Raphaelson. "The absolute risk was increased by a factor of 2, but in this study, that was not statistically significant. It's important for the word to get out; if these data are correct — and this is the best study to date — then that indicates that perhaps we shouldn't be so afraid of that complication in patients prescribed Ambien specifically or other similar sleeping pills."

He also agreed that the prevalence numbers for sleepwalking are high compared with those for other neurologic diseases. He used the example of epilepsy, with a prevalence of 0.5%, and Parkinson's disease, with a prevalence of 0.2% "That means it's very common; and neurologists and primary care doctors are seeing people who have this condition but often we're not recognizing it because we don't ask about it."

Definitions Confusing

Another neurologist approached for a comment, William Kohler, MD, medical director, Florida Sleep Institute, Spring Hill, said the study is useful but somewhat confusing in terms of the definitions it used.

"It's an important study because it gets the numbers out there about how common this is, but it would have been more valuable if we had a more succinct definition of what they were evaluating," said Dr. Kohler. "Are they talking sleep walking or this nocturnal wandering, and how does that different from sleep walking?"

The authors tried to differentiate nocturnal wandering from sleep walking — in discussing case reports, they said "it is impossible to tell whether the patient was sleepwalking or had episodes of nocturnal wandering (i.e. the patient is awake but is confused and has no memory of the episode upon awakening)" — but this, too, was confusing, said Dr. Kohler. "I would have liked more clarification."

Dr. Ohayon later clarified that sleepwalking and "confusional arousal" are both characterized by partial or complete amnesia of the episode; the differences can be seen only with a recording of brain activity.

"For a real sleepwalker, the recording will show the brain is asleep; for somebody with a confusional arousal episode, the brain recording will show that the individual is awake but there are some sleep intrusions in the brain activity," he said.

NW includes sleepwalking and confusional arousal, but it is a more general clinical symptom and doesn't require any electroencephalographic (EEG) confirmation.

Sleepwalking is a part of nocturnal wandering that is a diagnosis and not a symptom, and as a diagnosis, it can be confirmed by sleep recording although this is not necessary. "In fact, sleep walking can be recognized by its symptomatology but to treat the patient it is preferable to have his EEG recording."

The study was supported by the National Institutes of Health, the Arrillaga Foundation, the Bing Foundation, and Neurocrines Biosciences. Dr. Ohayon and the commentators have disclosed no relevant financial relationships.

Neurology. 2012;78:1583-1589. Abstract

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