Sleepwalking

Parasomnias are sleep-wake disorders characterized by undesirable motor, verbal, or experiential phenomena occurring in association with sleep, specific stages of sleep, or sleep-awake transition phases. In the American Psychiatric Association (APA) Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5), one common parasomnia, non-REM (NREM) sleep arousal disorder, is described as being characterized by either somnambulism (ie, sleepwalking) or sleep terrors. ^[1]

For patient education resources, see the Sleep Disorders Center, as well as Disorders That Disrupt Sleep (Parasomnias), Sleepwalking, and REM Sleep Behavior Disorder.

Diagnostic criteria (DSM-5)

The specific DSM-5 criteria for NREM sleep arousal disorder, sleepwalking type, are as follows ^[1] :

• Recurrent episodes of incomplete awakening from sleep, usually occurring during the first third of the sleep cycle, accompanied by episodes of rising from bed and walking about

• During sleepwalking episodes, a blank, staring face; relative unresponsiveness to efforts at communication; difficulty in awakening

• Little or no recall of dream imagery

• Amnesia for the episode

• The episodes cause significant distress or impairment in social, occupational or other areas of functioning

• The symptoms cannot be explained by another mental disorder, medical condition, or the effects of a drug of abuse or medication

In addition, if warranted, the sleepwalking type can be further differentiated into 1 of 2 subtypes:

• With sleep-related eating (SRE)

• With sleep-related sexual behavior (sexsomnia)

It was once theorized that sexsomnia occurred in individuals acting out their dreams as a consequence of an underlying psychological condition; however, such theories have been debunked. Sexual behaviors of all types may occur during a sleep automatism, ranging from explicit sexual vocalizations to violent masturbation to complex sexual acts that may include fondling, cunnilingus, fellatio, and even vaginal and anal sex. ^[2]

Features of sexsomnia are analogous to those of other NREM parasomnias that occur during what is known as a confusional arousal during the deeper stages of sleep. Throughout this time, the brain is in a hybridized state in which cortical areas (which control higher thought processing and reasoning) are deactivated while more primitive functions (eg, eating and sex) remain active. Individuals are typically amnestic for the episode. Those who commit these sexual acts typically have a family or personal history of other parasomnias.

In a small number of sexsomnia cases, medicolegal issues have arisen, though the actual forensic implications remain nebulous. Several of the cases have points in common—namely, the involvement of a male perpetrator younger than 35 years, accusations of sexual assault or rape, claims of amnesia after the event, and a history of prolonged complex somnambulism. This unusual parasomnia is more common than was previously thought; many patients with the behavior were identified only after specific questions were asked. ^{[3, 4]}

In addition to SRE, the literature describes another disorder involving the consumption of food during the night or at bedtime: night-eating syndrome (NES). A clear distinction should be drawn between SRE and NES: the latter is not categorized as a parasomnia, because full consciousness is maintained during NES episodes.

Although NES was first described by Stunkard et al in 1955, no uniform definition of this disorder has yet been adopted. NES is characterized by consumption of excessive amounts of food either before bed or during nocturnal awakenings. It is up to 4 times more common in females and tends to have an onset in late adolescence. ^{[5, 6]} According to the most commonly used current definition, NES is present if patients report the following:

• Skipping breakfast 4 or more days per week (interpreted as morning anorexia)

• Consuming more than 50% of total daily calories after 7:00 PM

• Difficulty in falling asleep or staying asleep 4 or more days per week

Whether NES should be differentiated from nocturnal eating syndrome is not clear in the literature. However, the terms may be usefully distinguished as follows ^[7] :

• NES may be defined as morning anorexia, evening hyperphagia, and insomnia

• Nocturnal eating syndrome may be defined as eating at night after having gone to bed

SRE, on the other hand, can be conceptualized as a binge eating disorder that incorporates the disordered arousal, confusional behavior, and amnesia of an NREM parasomnia. ^[8] Episodes often occur within the first 2-3 hours of sleep, with ingestion of foods (commonly high in carbohydrates) in a hurried, uncontrollable manner. In contrast to other NREM parasomnias, a fluctuation in level of awareness exists between episodes within the same night. There is relatively high comorbidity with restless legs syndrome (RLS). ^[9]

The parasomnias have been thought to represent not pathologic cerebral functioning but, rather, a response to central nervous system (CNS) activation that results in sleep-wake or rapid eye movement (REM)–NREM state confusion, instability, or overlap. However, studies have demonstrated differences between sleep patterns and neuronal sleep control mechanisms in individuals who have parasomnias and corresponding patterns and mechanisms in individuals who do not.

Normal sleep involves cyclic hypnic patterns throughout the night between wakefulness, NREM, and REM states. The CNS remains active during all sleep-wake states, though rapid changes are required in neural networks, rhythms, and neurotransmitters with state changes. The length of each cycle averages 50 minutes for a full-term newborn, increasing to approximately 90 minutes by adolescence.

Slow-wave sleep (SWS) normally occurs in the first 2 hypnic cycles; younger children have an additional SWS period toward the end of the sleep period. Children typically enter their deepest sleep within 15 minutes of sleep onset, and this first SWS period lasts from 45-75 minutes. This explains why it is easy to move children without rousing them soon after sleep onset.

Parasomnias occur as children are caught in a mixed state of transition from one sleep cycle to the next (eg, from NREM sleep to wakefulness). This transition state is characterized by a high arousal threshold, mental confusion, and unclear perception.

Sleepwalkers appear to have an abnormality in SWS regulation. The dissociation that occurs between body and mind sleep appears to arise from activation of thalamocingulate pathways with persisting deactivation of other thalamocortical arousal systems. The first SWS period of the night is considered to be more disturbed in somnambulistic individuals, and the entire NREM-REM sleep cycle is more fragmented. Because these disorders occur more frequently in children, these differences have been suggested as signs of CNS immaturity.

Genetic factors

Sleepwalking occurs more frequently in monozygotic twins and is 10 times more likely if a first-degree relative has a history of sleepwalking. An increased frequency of DQB1*04 and *05 alleles is reported. DQB1 genes have also been implicated in narcolepsy and other disorders of motor control during sleep (eg, REM behavior disorder).

Environmental factors

Sleep deprivation, chaotic sleep schedules, fever, stress, magnesium deficiency, and chemical or drug intoxication (eg, alcohol) can trigger parasomnias. Various medications can also serve as triggers, including the following:

• Sedative-hypnotics (eg, zolpidem ^[10] )

• Combination of valproic acid and zolpidem ^[11]

• Antidepressants (eg, bupropion ^[12] , paroxetine, and amitriptyline)

• Neuroleptics (eg, lithium and reboxetine)

• Minor tranquilizers

• Stimulants

• Antibiotics (eg, fluoroquinolones)

• Antiparkinsonian medications (eg, levodopa)

• Anticonvulsants (eg, topiramate) ^[13]

• Antihistamines

Physiologic factors

The length and depth of SWS, which is greater in young children, may be a factor in the increased frequency of parasomnias in children. Conditions such as pregnancy and menstruation are known to increase frequency in patients with parasomnias.

Comorbid conditions

Medical conditions associated with parasomnias include the following:

• Arrhythmias

• Chronic paroxysmal hemicrania

• Migraine

• Fever

• Gastroesophageal reflux

• Nocturnal asthma

• Nocturnal seizures

• Obstructive sleep apnea - Children with obstructive sleep apnea or Tourette syndrome are at greater risk of having parasomnias along with their underlying disorder ^{[14, 15]}

Chronic sleepwalking, especially in adults, is frequently associated with sleep-disordered breathing. Treatment of the sleep-disordered breathing with continuous positive airway pressure (CPAP) or surgery typically improves or resolves the sleepwalking. Noncompliance with CPAP is associated with persistence or recurrence of sleepwalking. Serotonin has been postulated as the physiologic link between these 2 disorders.

Thyrotoxicosis has been associated with an increased incidence of sleepwalking, ^[16] and achievement of euthyroidism is associated with improvement or resolution of the symptoms. Sleepwalking may occur as an early symptom, and the onset of sleepwalking in a patient out of the normal expected age range warrants evaluation for hyperthyroidism. The mechanism for the sleepwalking is considered to be increased fatigue in combination with longer periods of NREM sleep.

Psychiatric disorders associated with parasomnias include the following:

• Posttraumatic stress disorder

• Panic attack

• Dissociative states

• Major depressive disorder

• Obsessive-compulsive disorder

United States and international statistics

Disorders of arousal are all more prevalent in children than in adults. Confusional arousals are reported in 5-15% of children. Sleep terrors have an incidence of approximately 1%. The lifetime prevalence of nocturnal wandering with abnormal state of consciousness among US adults may be as high as 29.2%. ^[17] ; however, the prevalence of sleepwalking disorder, marked by repeated episodes and impairment or distress, is much lower (1-5%). ^[1]

In Sweden, the incidence of quiet sleepwalking is reported as 40%, with a yearly prevalence of 6-17%. Only 2-3% report more than 1 episode per month, and 33% report only a single episode. In a survey of adults in the United Kingdom, 2.2% reported having night terrors, 2.0% reported sleep walking, and 4.2% reported confusional arousals.

Age-, sex-, and race-related demographics

Sleepwalking occurs most commonly in middle childhood and preadolescence, with a peak incidence in children aged 11-12 years. A Canadian study of sleep data from a cohort of 1,940 children born in 1997 and 1998 in Quebec found prevalence of sleepwalking peaked at age 10 years. Data also show that prevalence of childhood sleepwalking increases with the degree of parental history of sleepwalking: 22.5% (95% CI, 19.2%-25.8%) for children without a parental history of sleepwalking, 47.4% (95% CI, 38.9%-55.9%) for children who had 1 parent with a history of sleepwalking, and 61.5% (95% CI, 42.8%-80.2%) for children whose mother and father had a history of sleepwalking. ^[18]

Confusional arousals are most common in toddlers and preschool-aged children. Violent or sexual activity is more likely in adults. Sleepwalking and confusional arousals have an equal incidence in males and females. Females are more likely to sleep eat. Sleepwalking occurs more often in females during childhood but more often in males in adulthood. No racial predilection is known.

The NREM parasomnias are rarely associated with any significant morbidity or long-term sequelae. Although disruptive and frightening for parents in the short term, these disorders rarely cause injury (though children can strike objects during sleepwalking and occasionally become injured). The prognosis for resolution with maturation is excellent.

Sleep-disordered breathing and, to a lesser extent, RLS have been associated with sleepwalking in children, though less often than in adults. The incidence of associated sleep disorders has been reported to be as high as 61%. Prolonged disturbed sleep may be associated with school and behavioral issues. A relationship with hyperactivity is suggested but not clear.

In adolescents and adults, morbidity may be more significant. More complex motor behaviors (eg, driving a car, cooking, eating, or playing a musical instrument) have been reported. Behaviors injurious to the patient or bed partner may be associated with forensic medicine implications.

An increased incidence of psychiatric disorders such as neuroses, panic disorder, phobias, and suicidal ideations has been reported in both these groups. Sleep-disordered breathing, including a sense of choking or blocked breathing, has also been reported. The respiratory events may have a deleterious effect on sleep by increasing arousals and sleep fragmentation.

Adolescents with sleep terrors or sleepwalking have an increased prevalence of other sleep disorders, neurotic traits, and other psychiatric disorders.

Serious injury, sexual misconduct, and violent behavior occurring during somnambulism have been reported in adults, albeit rarely. Most serious injuries have occurred as a result of leaping through windows. Some apparent “suicides” have likely been the unfortunate result of a sleep behavior. The violent behavior aspect, though rare overall, appears to occur more frequently in men than in women. Such behavior toward others has occasionally been used as a legal defense.