Parasomnias are a group of sleep disorders involving undesirable behaviors or events during sleep. NREM parasomnias, also called disorders of arousal, occur during the sleep-wake transition and are initiated during non-rapid-eye-movement sleep or slow-wave sleep. People with NREM parasomnias experience abnormal arousal during sleep because the transition between sleep and wakefulness doesn’t function normally.
Symptoms of NREM parasomnias include engaging in behaviors during or just after sleep that mimic wakefulness. If the behaviors are recalled later, the recollection is usually cloudy and inaccurate. These actions can be dangerous, as is the case with sleepwalking, or undesirable, like sleep eating. They are more common in children than adults and typically occur during the first third of the night.
Types of NREM Parasomnias
There are several types of parasomnias associated with NREM sleep.
Confusional arousals are episodes of confusion, disorientation, and bizarre behavior immediately after awakening from sleep. These episodes last from 1 to 10 minutes and can include thrashing or kicking in bed.
Sleepwalking (somnambulism) involves a sequence of behaviors including sitting up in bed, moving around the bedroom, talking with eyes open, walking from room to room and sometimes leaving the home. During these episodes, the sleepwalker often appears uncoordinated and clumsy and may fall or trip. Sleepwalkers are difficult to wake and generally don’t recall the episode afterward. Up to 40 percent of children will experience at least one sleepwalking incident during childhood; up to 4 percent of adults sleepwalk.
During night terrors (also called parvor nocturnus or incubus attacks) a person will scream and seem panicked, often while sitting in bed. These “attacks” last up to three minutes and usually end with the person returning to sleep. People experiencing a night terror won’t recall the episode later. Night terrors have been reported in up to 7 percent of children and 2 percent of adults.
Sleep-related eating disorder (SRED) is characterized by recurrent episodes of consuming food—often high-calorie junk food—during sleep. Confusion, disorientation, and an inaccurate or absent memory of the event are components of SRED. The disorder combines aspects of sleepwalking with a binge-eating disorder. Up to 5 percent of adults may have SRED, which affects more than twice as many women as men.
What causes NREM Parasomnias?
NREM parasomnias may be caused by neurological disorders or linked to another sleep disorder. The risk of NREM parasomnias is strongly linked to family history; the DQB1 gene is associated with sleepwalking. NREM parasomnias are more common in children and usually outgrown by age 5; prevalence in adults is around 2 percent. Stress, sleep deprivation and medications that deepen sleep, like zolpidem (Ambien) increase the risk of NREM parasomnias.
Because NREM parasomnias sometimes result from another sleep disorder or sleep deprivation, polysomnography is often used to diagnose these disorders. A polysomnogram can monitor brain, heart, and lung activity overnight and rule out other disorders like sleep apnea or restless legs syndrome.
NREM parasomnias are usually outgrown in early childhood and generally harmless, so most of these sleep arousal disorders don’t require treatment. Doctors usually recommend treating underlying sleep disorders, avoiding sleep deprivation, removing dangers in the sleep environment (for example, blocking off stairs and locking sharp cutlery out of reach), and reducing stress.
In some cases, recurrent episodes that don’t respond to other treatments may be treated with benzodiazepines, including clonazepam, diazepam, and oxazepam or dopaminergic agents, opiates, topiramate, and trazodone.