Non-Rapid Eye Movement Sleep Arousal Disorders
Non-rapid eye movement (NREM) sleep arousal disorders involve repeated episodes of incomplete awakening from sleep, most commonly sleepwalking or night terrors (also known as sleep terrors), but occasionally more complex behaviors. These episodes usually happen during the first third of the night, and people have no memory of the episodes in the morning. NREM sleep arousal disorders occur most commonly in childhood and less often as people age.
People experiencing NREM sleep arousal are considered partially asleep and partially awake during episodes, which usually last no more than 10 minutes, although one can occasionally extend to an hour. As the individual’s eyes are typically open during these episodes, they can be disconcerting for partners or family members who witness them.
For a diagnosis of NREM sleep arousal disorders to be made, episodes must cause the individual clinically significant distress or impairment—or significantly disrupt the lives of members of their households. Episodes can indeed disrupt social, romantic, or familial relationships, and cause significant embarrassment to the person experiencing them. A clinician will generally consider the disruptive effects of the episodes more than their frequency when determining a diagnosis or treatment path.
The term sleepwalking does not only refer to walking but can apply to a range of behaviors, some complex, which can also include talking in one’s sleep and using the bathroom. Generally sleepwalking involves rising from bed and walking around; as with other NREM sleep arousal episodes, these are most likely to occur in the first third of the night, during slow-wave sleep.
An individual who is sleepwalking has reduced alertness and responsiveness and a blank stare. They will generally not respond to efforts by others to wake them or talk to them. If they are awakened during an episode they could be disoriented for a time, and will likely have no or limited recall for the episode, but will then experience a full recovery of cognitive function and appropriate behavior.
Yes, but it is not common. Sleepwalkers have been reported to drive cars—even motorcycles—or otherwise venture out into the world while being basically unconscious. On rare occasions, sleepwalkers have committed violent acts, including murder. Some individuals have fallen off of roofs or seemed to die by suicide while apparently sleepwalking, although it is extremely rare and the individual’s state of mind in such episodes is difficult to confirm.
Yes. Sleep-related eating behavior and sleep-related sexual behavior (known as sexsomnia) are specific, less-common forms of sleepwalking. Individuals with sleep-related eating can experience repeated, unintentional episodes of eating. In these cases, many will have no memory of the episodes, as with other forms of sleepwalking, but some people report being fully aware of the behavior while being powerless to stop it. During epi­sodes, people may consume inappropriate foods.
A person who experiences sexsomnia may engage in masturbation, fondling, groping, or actual sexual intercourse while sleeping, without conscious awareness: The individual engaging in these behaviors may have their eyes open and may speak or make noises, but they will generally appear vacant or blank, “glassy-eyed,” and/or nonresponsive, and they will typically not remember the episode when they awaken. In women, the condition most often manifests as masturbation while sleeping. Men exihibit a wider range of behaviors including engaging in intercourse. The prevalence of sexsomnia is unknown because so few people with the condition are aware they have it, but it is more common in males and it can have serious negative social and even legal consequences.
Night terrors involve repeated awakenings from deep sleep by intense fear, usually beginning with a cry or scream of panic; as with other NREM sleep arousal episodes, these are most likely to occur in the first third of the night, during slow-wave sleep. Episodes typically begin with the individual abruptly sitting up in bed and screaming or crying. A night terror generally lasts 1-10 minutes but some children may experience significantly longer episodes.
The behavioral manifestation of a night terror is driven by intense fear and, often, a sense of dread and an urge to escape. The individual experiencing it will have a frightened expression and display signs of intense anxiety like sweating or rapid breathing. The person is difficult to awaken or comfort and if they do awaken or are awakened, they will generally remember very little about the experience, although older children and adults are increasingly likely to recall the fearful images sometimes associated with night terrors. (Episodes usually don’t involve complete stories as dreams or nightmares might.)
No. Nightmares tend to occur later in the evening, most often during REM sleep. People can awaken from nightmares easily and completely, and often can remember what was occurring in the scary or disturbing dream.
No. People with REM sleep behavior disorder react physically to what they are dreaming, vocalizing, screaming, or engaging in complex and sometimes violent motor behaviors. Such “dream enacting behavior” typically reflects the content of action-filled or violent dreams in which a person is being attacked or trying to escape danger, but any such episode would be distinct from a night terror. Unlike night terrors, REM sleep behavior disorder generally occurs in people over 50, and those individuals can remember the content of the involved dreams.
Yes, but at different times. The underlying mechanism causing NREM sleep disorders—the simultaneous occurrence of wakefulness and NREM sleep—is the same for both behaviors so an individual can experience both.
NREM sleep behavior disorder appears to have a strong genetic component. A family history may be present in up to 80 percent of people who experience sleepwalking, and when both parents have a history of sleepwalking, their children have more than a 50/50 chance of developing the condition themselves. Someone with a first-degree biological relative who has experienced night terrors may be as much as 10 times more likely to experience them themselves, as compared to those without such a family history.
Occasional incidences of NREM sleep arousal are fairly common; 10 to 30 percent of children have had at least one episode of sleepwalking, and 2 to 3 percent of children sleepwalk often. The prevalence of occasional sleepwalking episodes among adults is estimated between 1 and 7 percent, but fewer than 1 percent of adults experience sleepwalking as frequently as once a month.
The rate of sleep terrors is more difficult to estimate. It may affect as many as one in five children before age 3, but the prevalence among adults is about 2 percent.
Sleepwalking occurs more often in females during childhood and more often in males during adulthood. Eating during sleepwalking episodes is more common in females, while sexsomnia is more common in males. Sleep terrors are more common in boys than girls, but among adults, the sex ratio appears to be even.
The occurrence of NREM sleep arousal disorders in adults who did not experience episodes as children is rare. When it occurs, generally in the form of sleepwalking, clinicians should investigate potential causes such as sleep apnea, nocturnal seizures, or the side effects of medication.
Yes, several risk factors can increase the likelihood of episodes in people who may be prone to episodes of NREM sleep behavior disorder, including sedative use, fever, sleep deprivation, sleep schedule disruptions, exhaustion, and physical or emotional stress.
Treatment approaches for NREM sleep behavior disorder will depend on the severity of the condition. Most children, for example, grow out of the disorder in time. So, while it may be disturbing for their parents, sometimes intensely so, the child is neither aware of the behavior nor in any physical danger and no treatment may be necessary.
For those of any age experiencing episodes, establishing better sleep habits, starting with getting enough sleep each night, may help reduce their frequency. Alcohol use should also be reduced among adults with this condition.
When episodes are frequent or create a dangerous situation for an individual or their bed partner, changes can be made in the sleep environment to promote safety. Such changes can include:
- Padding the floor around the bed with a mattress or pillows
- Padding corners of nearby furniture
- Window protection
- Removing dangerous objects, such as guns or sharp objects, from the bedroom area
- Locking doors and windows
- Sleeping in a separate room from the bed partner until symptoms are under control
In severe cases, medication may be prescribed to reduce the frequency of episodes.