New research about sleepwalking has raised questions about several common beliefs regarding this frequently misunderstood sleep disorder. Researchers at the University of Montreal conducted a comprehensive review of more than 15 years of study on the topic of sleepwalking. Their analysis produced what may be a clearer picture of the sleep disorder, its possible mechanisms, and its risk factors. Their analysis also challenges some common beliefs about sleepwalking—beliefs that, if outdated, could interfere with diagnosis and treatment.
What are these views on sleepwalking that researchers say are not supported by data? There are three primary ones, which involve the experience of activities during sleepwalking as well as the daytime effects of the disorder. Researchers say that the cumulative data challenges these three notions:
Researchers found, in fact, that the memory recall can vary, with some sleepwalkers retaining memories of their episodes and others not. During an episode of sleepwalking, people are in a state that researchers call “dissociated arousal,” with parts of the brain in a sleeping state and other parts of the brain in a waking state. This may help to explain why some can remember their experiences while others cannot.
Scientists also found evidence to contradict the common belief that people’s actions during sleepwalking are simply irrational, lacking any underlying motivation. The accumulated data, researchers say, suggests otherwise. It is true that episodes of sleepwalking often include strange and seemingly irrational behavior. But researchers found that sleepwalkers who were able to recall their actions during these episodes could also identify a rationale for their behavior, even in circumstances where their actions later seemed strange to them. This led researchers to conclude that sleepwalkers retain motivation for their actions during episodes.
Contrary to the view that the effects of sleepwalking are confined to nighttime episodes, this analysis found that sleepwalkers do experience daytime effects from the disorder. A high percentage of sleepwalkers—nearly 45%--reported daytime sleepiness. Sleepwalkers perform less well on vigilance tests than those without the disorder. And sleepwalkers who were allowed to nap during the day fell asleep more quickly than those who did not sleepwalk.
Other conclusions that came from this analysis aligned with recent research on sleepwalking. One has to do with genetics. The current review found that nearly 80% of sleepwalkers have a family history of the sleep disorder. Researchers identified stress and fatigue as possible causes of sleepwalking, but said that for people who have a genetic predisposition, any disruption to sleep might trigger the disorder.
This conclusion is in line with previous studies, which also found family history linked strongly to the disorder. In this study, researchers at Stanford University investigated sleepwalking and found a strong family connection, with more than 30% of the study population able to identify least one other family member with the sleep disorder. The Stanford study, reported in 2012, also found sleepwalking to be significantly more common than often is thought. Stanford researchers found as many as 3.6% of U.S. adults may experience some form of nocturnal wandering during any given year. And when sleepwalking is considered over the course of a lifetime, including childhood, as many as 30% of the population may have some experience of the disorder.
Sleepwalking is more common during childhood, a conclusion confirmed by this latest research review. Data indicates that sleepwalking is most common in children ages 6-12. Researchers link childhood prevalence of sleepwalking to brain development, and the readiness of a young brain to successfully complete the complicated neurological task of transitioning from wake to sleep. Very often, episodes of sleepwalking will diminish and disappear altogether during adolescence. But as many as 25% of adolescent sleepwalkers will continue to have episodes during adulthood, researchers say.
Sleepwalking in adulthood will also decrease with age. This is related to a diminished amount of time spent in the phases of deep sleep, also known as slow-wave sleep. Sleepwalking occurs during periods of slow-wave sleep. As we age, we naturally spend less time in slow-wave sleep, and sleepwalking tends to occur with less frequency. Researchers conducting the review point to evidence of abnormalities in the slow-wave sleep of sleepwalkers, including repeated episodes of “micro-arousals.” Further study into the slow-wave sleep of people who experience sleepwalking may shed important light on the underlying causes and triggers for the disorder.
What about the dangers of sleepwalking? The current research review indicates that sleepwalking overall is not particularly dangerous, that its episodes are brief and usually harmless to sleepwalkers and their bedmates. However, other recent research paints a very different picture, one that suggests sleepwalking poses significant risks for physical harm. Among sleepwalkers in this study, 58% experienced some kind of violent sleep-related behavior, and 17% had at least one episode that required medical treatment for either the sleepwalker or a bed partner.
We’ve got a long way to go in our understanding of the causes and behaviors of sleepwalking. I hope this latest review will spur more interest in the questions that remain unanswered by this often overlooked sleep disorder.
Michael J. Breus, PhD
The Sleep Doctor™