Kushida, CA: Handbook of Sleep Disorders, Chapter 36 – Nielsen and Petit1
Overview of the parasomnias
What are parasomnias?
What are the social and economic costs of parasomnias?
What are REM sleep parasomnias?
Nightmare disorder
Recurrent isolated sleep paralysis
REM sleep behavior disorder
What are NREM sleep parasomnias?
Confusional arousals
Sleepwalking (somnambulism)
Sleep terrors
What other parasomnias are there?
Sleep enuresis
Sleep-related bruxism
Sleep-related rhythmic movement disorder
Somniloquy
Sleep-related groaning
References
What are parasomnias?
The American Academy of Sleep Medicine defines parasomnias as “undesirable physical events or experiences that occur during entry into sleep, within sleep or during arousals from sleep”.1 They are varied in their expression, ranging from simple movements (rocking, grinding, and groaning) to complex, seemingly purposeful behaviors (sleepwalking, REM behavior disorder). Most parasomnias are considered to be normal sleep phenomena and benign, especially when they occur in children. The incidence and prevalence of these undesirable sleep events decreases significantly with the onset of adolescence. In some cases they can lead to injuries, psychological distress and sleep disturbances for both the individual and family members. In legal cases of sleep-related violence (when a diagnosis of parasomnia has been established), parasomnias involve behaviors that are not clearly motivated, are devoid of sound judgment and not under conscious deliberate control.
Parasomnias include many conditions with different pathophysiologies and responses to treatment. They are currently classified into primary parasomnias, which are disorders of sleep states per se, and secondary parasomnias, which are disorders of specific organ systems that manifest preferentially during sleep. Primary parasomnias are further classified into 1) disorders associated with NREM [non-REM] sleep (aka disorders of arousal), 2) parasomnias associated with REM sleep and 3) other parasomnias. Each of these divisions is further subdivided into more specific parasomnia types; subdivisions for the primary parasomnias are shown in Table 1.
Table 1. Primary parasomnias classified by sleep stage
Parasomnias associated with NREM sleep / Parasomnias associated with REM sleep / Other parasomniasConfusional arousals / Nightmare disorder / Sleep enuresis
Somnambulism / Recurrent isolated sleep paralysis / Sleep-related bruxism
Sleep terrors / REM sleep behavior disorder / Rhythmic movement disorder
Somniloquy
Nocturnal groaning
What are the social and economic costs of parasomnias?
Sleep is central to good health and daily functioning. Yet the full scale of the social and economic costs incurred by sleep disorders is not yet completely clear. For 2004, the direct and indirect cost of sleep disorders as a whole was estimated to be $7.5 billion for the Australian population (20.1 million people). This would translate to about $109 billion for the United States2 and $12.3 billion for Canada. But little is known about the economic impact of specific parasomnias. At least two parasomnias, sleepwalking and RBD, warrant more immediate attention because of the injuries and severe sleep disruption they often inflict on patients and their families.
Adult sleepwalkingcan lead to the destruction of property such as the breaking of walls, doors, windows and plumbing. Behaviors reported for either somnambulism or sleep terrors include running into walls and furniture, jumping out of windows, driving a car, wandering around streets, climbing ladders, sexual activity and manipulating weapons—even loaded shotguns. The fact that somnambulistic episodes can consist of complex and organized behaviors such as suspected suicide, attempted homicide and homicide, raises important medico-forensic questions.3-12The number of legal cases of sleep-related violence is on the rise13.
RBDcan frequently lead to serious injuries 14,15 and are a main reason for clinical consultation. RBD episodes may also cause severe sleep disruption for the bed partner and major marital discord, mood changes, even suicide attempts.16 Beyond these consequences, RBD may be a prodrome for neurodegenerative diseases, especially Parkinson and Lewy body diseases. In fact, 45% of patients with RBD develop either Parkinson disease, Lewy body disease or multisystemic atrophy after a follow-up of only 5 years.17 A longer follow-up (11 years) reveals that 65% of RBD patients develop a neurodegenerative disorder leading mainly to dementia.18
What are REM sleep parasomnias?
Nightmare disorder
Clinical features
Nightmare disorder is the persistence of disturbing dreams that arise primarily from REM sleep (more rarely from stage 2 sleep) and that usually end up awakening the sleeper.1 Autonomic activation is usually much less than in sleep terrors. There may be dream-enacting behaviorsat the end of some nightmares, especially if you are enduring a situation of intense emotional stress and/or sleep disruption, e.g., the postpartum state.19 Awakenings from nightmares are usually abrupt and a detailed disturbing dream is easily recalled. Idiopathic nightmares have no apparent cause and are distinguished from post-traumatic nightmares, which are due to trauma.
Incidence and prevalence
The prevalence of nightmare symptoms is estimated together with their frequency. Nightmares occur occasionally in over 85% of the general population, at least once a month in 8-29% and at least once a week in 2-6%.20-23 A frequency of one nightmare per week likely reflects clinical pathology. Nightmares are less frequent among preschoolers (1.5-3.9% parents report their children have them often or always) than previously thought but may appear as early as 29 months and remain highly stable until age 6 yrs.24 An internet survey of 24,102 respondents25 found the number of nightmares recalled per month peaks between ages 20-29 and then declines steadily. A second internet survey of 3978 respondents found that the distress caused by nightmares increased abruptly at an earlier age for women than for men. A gender difference favoring girls appears in adolescence26,27 and continues throughout the lifespan, as shown in Figure1.25
Figure 1.
Retrospective estimates of monthly nightmare frequency by 5-year age strata in an internet sample of 24,000 respondents.25 *=significant difference between female and male subjects at that stratum, p<.05
Polysomnographic characteristics
Nightmares are often associated with autonomic fluctuations (increased heart and respiratory variability) during REM sleep. But these fluctuations are often less than might be expected from hearing the content of the nightmare.28 In contrast, post-traumatic nightmares are accompanied by heightened reactivity in the form of more frequent awakenings,29 longer time awake after sleep onset,29,30 increased motor and rapid eye movement activity during REM sleep,31-33 and higher REM and NREM sleep respiration rates.34Both idiopathic and post-traumatic nightmare patients have elevated levels of periodic leg movements (PLMs) in REM and NREM sleep.29
Associated factors
A genetic contribution to nightmares has been found to be 44% for men and 45% for women in the case of childhood nightmares.35 Bad dreams among 29-month-old preschoolers are predicted by mother ratings of difficult temperament as early as 5 months of age and by mother and father ratings of child anxiety as early as 17 months.24 Among adults, nightmares are also associated with psychopathological traits36,37 and personality variables such as:
physical and emotional reactivity36,38
fantasy proneness39
thin boundaries.40-43
Nightmares are more frequent and prevalent in psychiatric populations23,44 and are associated with pathological symptoms such as anxiety, neuroticism, posttraumatic stress disorder, schizophrenia-spectrum symptoms, suicide risk, dissociative phenomena, problematic health behaviors and sleep disorders (see reviews45,46). Nightmares are also more likely during periods of increased life stress.38,47,48
Recurrent isolated sleep paralysis
Clinical features
Recurrent isolated sleep paralysis (aka isolated sleep paralysis or sleep paralysis, SP) is common and generally benign, being characterized by brief episodes of motor or vocal paralysis combined with a waking state of consciousness.1 Frightening dreamlike hallucinations often intrude and can cause considerable distress. SP episodes occur at sleep onset (hypnagogic) and upon awakening (hypnopompic) and is one characteristic of individuals with narcolepsy, which is characterized by cataplexy and excessive daytime sleepiness in addition to SP and hypnagogic hallucinations.1 SP is commonly associated with feelings of fear or terror49 and are often linked to the hallucination of an unseen presence in the room (‘sensed presence’).50,51
Incidence and prevalence
Variations in prevalence estimates (5-40%) depend upon differences in operational definitions, age of subjects and sociocultural factors.52-54 Age of onset is typically 14-17 yrs. Accompanying sensed presence hallucinations occur in 60-69% of cases.50,51,55,56
Polysomnographic characteristics
SP episodes most often arise from sleep-onset REM periods (see Figure 2),57,58 leading to the view that the episodes are bouts of state dissociation during which some REM sleep mechanisms–muscle atonia and vivid dreaming in particular–intrude upon the waking state.59,60
Figure 2.
Somnograms of five healthy subjects reporting sleep paralysis episodes during a multiphasic sleep-wake schedule. Vertical arrows above somnograms indicate awakening points where sleep paralysis episodes were reported. Of 184 awakenings, 8 sleep paralysis episodes were recorded; 2 just prior to impending REM episodes (spontaneous awakenings) and 6 from sleep onset REM episodes (from Takeuchi, et al., 2002).58
Associated factors
Among the factors associated with sleep paralysis episodes are stress,54,58,61 shift work and irregular sleep-wake schedules.53,61 A genetic component has also been reported, e.g., 36% of respondents in a Japanese sample had family members who experienced sleep paralysis.62
Several studies link sleep paralysis to various neurological and psychiatric disorders. It is predicted by bipolar disorder, automatic behavior and use of anxiolytic medications.52 It is also comorbid with PTSD,63,64 depression symptoms,65,66 anxiety disorder with agoraphobia,67 panic disorder,64,68,69 generalized anxiety disorder and social anxiety.70 This wide comorbidity has recently been attributed to mediation by an affect distress personality style (‘sleep paralysis distress’) in a manner analogous to that proposed for nightmare disorder (‘nightmare distress’).50
Associations of SP with psychiatric conditions vary among ethnic groups. Atypically high rates were found in African Americans with panic disorders,69 Moroccan patients,71 Magrebins71 and Cambodians.63 Some of these differences may stem from cultural interpretations of sleep paralysis hallucinations, sensed presence in particular, as a form of spiritual entity, e.g., “ghost oppression” in China,61 “Old Hag” in Newfoundland,72“the ghost that pushes you down” in Cambodia,63 among many others.
REM sleep behavior disorder
Clinical features
REM sleep behavior disorder (RBD), first described as a clinical entity in 1986,73 is characterized by the loss of skeletal muscle atonia normally present during REM sleep and the occurrence of complex dream-enacting motor behaviors. Diagnostic criteria include a) complaint of violent or injurious behaviors during sleep, b) limb or body movements associated with dream mentation and c) one of the following:
harmful or potentially harmful sleep behaviors
dream appears to be acted out
sleep behaviors disrupt sleep continuity.
In addition, the dream process and its content appear altered. Most patients (87%) report that their dreams become more vivid, intense, action-filled, and violent with the onset of RBD.74 Dream themes associated with behaviors are largely stereotyped in structure and emotional content.73,75 Among published reports of dreams for which investigators identified specific behaviors, the most frequent pattern is of vigorous defense against attacks by people (58.8%) and animals (23.5%) (see review76). Analyses of recently remembered dreams reveal a high percentage of aggressive contents but, paradoxically, normal levels of aggressiveness during the daytime.77
Sleep behaviors can produce injuries to the patient or the bedpartner; these might include ecchymoses, lacerations, fractures and subdural hematomas. Injuries are a main reason for consultation, being reported by 79%-96% of consulting cases.14,15
Incidence and prevalence
The prevalence of RBD is still largely unknown. A telephone survey of violent and injurious sleep behaviors in the British general population (N=4972; 15-100 yrs of age) produced a prevalence of about 0.5 %.78 Another study of 1034 Hong Kong area residents (70+ yrs) found a prevalence of 0.4%.79 It is predominant in males (87%), primarily men over age 50.74 Milder forms of RBD with less aggressive behaviors that do not lead to clinical consultation have been postulated for women.74 Also, dream-enacting behaviors among healthy young students and pregnant and postpartum women have recently been identified by our group.19,80
Polysomnographic characteristics
Laboratory recordings reveal intermittent or complete loss of REM sleep muscle atonia and excessive phasic EMG activity during REM sleep.75 The PSG diagnostic criteria are presence of:
a)excessive augmentation of chin EMG tone
b)excessive chin or limb phasic EMG twitching
c)one of the following features during REM sleep:
excessive limb or body jerking,
complex, vigorous or violent behaviours
absence of epileptic activity.
Compared with age-matched controls, RBD patients have more SWS81 and distinct changes in the EEG spectrum (e.g., more NREM delta,81 less REM occipital beta,82 more theta in several areas).
Associated factors
RBD is strongly associated with neurodegenerative diseases, especially the synucleinopathy type83 which include:
Parkinson’s disease,84,85
dementia with Lewy bodies,86-88
multiple system atrophy.89-91
RBD is also comorbid with two tauopathies: Alzheimer’s disease92 and progressive supranuclear palsy.93
Even patients with idiopathic RBD show some signs of neurodegeneration. FDG-PET brain imaging of cognitively normal patients with dream-enacting behaviors revealed lower metabolic activity in several brain regions known to be affected in dementia with Lewy bodies.94
Multiple dysfunctions for RBD patients have been described, including:
olfactory deficits95
color identification deficits95
decreased motor speed95
EEG slowing,82
mild dysautonomia96,97
subtle neuropsychological dysfunctions.82,98,99
RBD has also been associated with narcolepsy and other neurological disorders,75 such as:
olivopontocerebellar degeneration
ischemic cerebrovascular disease
multiple sclerosis
Guillain-Barré syndrome
Shy-Drager syndrome
Arnold-Chiari syndrome.
What are NREM sleep parasomnias?
Confusional arousals
Clinical features
Confusional arousals (aka sleep drunkenness) are transitory states of confusional behavior or thought occurring during or after awakenings from NREM sleep, usually from NREM sleep early in the night. The individual is confused, disoriented, behaviorally slow, and may display automatic or inappropriate behaviors. Vivid dreaming is usually not present. Sleep-related abnormal sexual behaviors, such as masturbation, sexual molestation, initiation of sexual intercourse and loud sexual vocalizations during sleep are part of the spectrum of confusional arousals.1
Incidence and prevalence
The incidence is unknown but episodes are frequent in early childhood and diminish after age 5.100 Young children with persisting confusional arousals often become sleepwalkers in adolescence. Prevalence in adults is 3-4 %101. There is no known gender difference.
Polysomnographic characteristics
The arousals usually occur during the first two NREM episodes, but can also occur in later NREM sleep. PSG recordings have shown awakenings from NREM sleep.
Associated factors
Childhood confusional arousals are usually benign; in adults they are often associated with mental disorders or obstructive sleep apnea. They occur more often in night-shift or rotating-shift workers.101 Many conditions can set the stage for confusional arousals:
family history
sleep deprivation
obstructive sleep apnea
drug/alcohol use.
Sleepwalking (somnambulism)
Clinical features
Sleepwalking is characterized by behaviors usually initiated during arousals from NREM sleep; it may begin with simple movements, such as sitting up in bed, and culminate in walking, running out of the room,1 or, more rarely, more complex activities, e.g., cooking or eating,102 driving,11 even homicide.3,103-106 Episodes are accompanied variously by amnesia, confusion, perceived threat, dreaming or even pseudo-hallucination. Usually considered benign in children, sleepwalking in adults may lead to injuries.
Incidence and prevalence
Peak incidence (approximately 17%) is around age 12 years.107 For adults, a suggested prevalence of 2-2.5%21,52 is probably an underestimate. Many studies report no gender difference in older children, adolescents or adults,107,108 but studies of young children 2.5-6 and 4-9 years old found it to be more common in boys than in girls.109,110
Polysomnographic characteristics
Sleep architecture does not differ between adult somnambulistic patients and control subjects,111-116 except that somnambulists have more arousals out of NREM sleep.111,113 Episodes of somnambulism are rare in the sleep laboratory, but they may be triggered experimentally by extended sleep deprivation (e.g., 38 hours).117,118
Associated factors
There is a strong genetic component119 with a link to the HLA-DQB1 gene.120 Anxiety may increase occurrences.100,121,122
Sleep terrors
Clinical features
Sleep terrors (aka night terrors or pavor nocturnus) are “arousals from SWS accompanied by a cry or piercing scream and autonomic nervous system and behavioral manifestations of intense fear”.1Typically, within 90 minutes of falling asleep, the individual screams and sits up with a panic-stricken expression and intense autonomic activity (sweating, racing heart, rapid breathing). Less often there are complex behaviors such as leaving the bed, fleeing the room or thrashing around. Injuries may result in such cases.123 Inconsolability is a key feature; attempts to console or awaken a somnambulist in mid-episode may well prolong or intensify it—even causing aggressive actions toward the intervener. As is the case for somnambulism and confusional arousals, the individual usually does not wake up fully from a sleep terror and will forget the event the following day. Sleep terrors do not differ markedly from somnambulism except that the behaviors displayed are usually more rapid and abrupt than during somnambulism.
Incidence and prevalence
Reported incidence estimates are variable.108,124-126 Some parents may fail to differentiate nightmares and sleep terrors but when a clear definition is supplied, a high prevalence (40%) is seen in preschoolers.110 Sleep terrors tend to resolve in adolescence and do not display a gender difference.108,110 In adults, there is a high degree of overlap among confusional arousals, somnambulism and sleep terrors.