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|Specialty||Clinical psychology, Psychiatry, Sleep medicine, Neurology|
A sleep disorder, or somnipathy, is a medical disorder of an individual's sleep patterns. Some sleep disorders are severe enough to interfere with normal physical, mental, social and emotional functioning. Polysomnography and actigraphy are tests commonly ordered for some sleep disorders.
Sleep disruptions can be caused by various issues, including teeth grinding (bruxism) and night terrors. When a person struggles to fall asleep and/or stay asleep with no obvious cause, it is referred to as insomnia.
Sleep disorders are broadly classified into dyssomnias, parasomnias, circadian rhythm sleep disorders involving the timing of sleep, and other disorders including ones caused by medical or psychological conditions.
The most common sleep disorder is insomnia. Others include sleep apnea, narcolepsy and hypersomnia (excessive sleepiness at inappropriate times), sleeping sickness (disruption of sleep cycle due to infection), sleepwalking, and night terrors. Management of sleep disturbances that are secondary to mental, medical or substance abuse disorders should focus on the underlying conditions.
Primary sleep disorders are common in both children and adults. However, there is a significant lack of awareness in children with sleep disorders, due to most cases being unidentified. Several common factors involved in the onset of a sleep disorder include increased medication use, age-related changes in circadian rhythms, environmental and lifestyle changes  and pre diagnosed physiological problems and stress. The risk of developing sleep disorders in the elderly is especially increased for sleep disordered breathing, periodic limb movements, restless legs syndrome, REM sleep behavior disorders, insomnia and circadian rhythm disturbances.
List of conditions
There are a number of sleep disorders. The following list includes some of them:
- Bruxism, involuntary grinding or clenching of the teeth while sleeping
- Catathrenia, nocturnal groaning during prolonged exhalation
- Delayed sleep phase disorder (DSPD), inability to awaken and fall asleep at socially acceptable times but no problem with sleep maintenance, a disorder of circadian rhythms. Other such disorders are advanced sleep phase disorder (ASPD), non-24-hour sleep–wake disorder (non-24) in the sighted or in the blind, and irregular sleep wake rhythm, all much less common than DSPD, as well as the situational shift work sleep disorder.
- Fatal familial insomnia, an extremely rare genetic disorder that causes a complete cessation of sleep, leading quickly to death by sleep deprivation
- Hypopnea syndrome, abnormally shallow breathing or slow respiratory rate while sleeping
- Idiopathic hypersomnia, a primary, neurologic cause of long-sleeping, sharing many similarities with narcolepsy
- Insomnia disorder (primary insomnia), chronic difficulty in falling asleep and/or maintaining sleep when no other cause is found for these symptoms. Insomnia can also be comorbid with or secondary to other disorders.
- Kleine–Levin syndrome, a rare disorder characterized by persistent episodic hypersomnia and cognitive or mood changes
- Narcolepsy, characterized by excessive daytime sleepiness (EDS) and so-called “sleep attacks,” relatively sudden-onset, irresistible urges to sleep, which may interfere with occupational and social commitments. About 70% of those who have narcolepsy also have cataplexy, a sudden weakness in the motor muscles that can result in collapse to the floor while retaining full conscious awareness.
- Night terror, Pavor nocturnus, sleep terror disorder, an abrupt awakening from sleep with behavior consistent with terror
- Nocturia, a frequent need to get up and urinate at night. It differs from enuresis, or bed-wetting, in which the person does not arouse from sleep, but the bladder nevertheless empties.
- Parasomnias, disruptive sleep-related events involving inappropriate actions during sleep, for example sleepwalking, night-terrors and catathrenia.
- Periodic limb movements in sleep (PLMS), sudden involuntary movement of the arms and/or legs during sleep. In the absence of other sleep disorders, PLMS may cause sleep disruption and impair sleep quality, leading to periodic limb movement disorder (PLMD).
- Other limb movements in sleep, including hypneic jerks and nocturnal myoclonus.
- Rapid eye movement sleep behavior disorder (RBD), acting out violent or dramatic dreams while in REM sleep, sometimes injuring bed partner or self (REM sleep disorder or RSD)
- Restless legs syndrome (RLS), an irresistible urge to move legs.
- Shift work sleep disorder (SWSD), a situational circadian rhythm sleep disorder. (Jet lag was previously included as a situational circadian rhythm sleep disorder, but it does not appear in DSM-5, see Diagnostic and Statistical Manual of Mental Disorders for more).
- Sleep apnea, obstructive sleep apnea, obstruction of the airway during sleep, causing lack of sufficient deep sleep, often accompanied by snoring. Other forms of sleep apnea are less common. Obstructive sleep apnea (OSA) is a medical disorder that is caused by repetitive collapse of the upper airway (back of the throat) during sleep. For the purposes of sleep studies, episodes of full upper airway collapse for at least ten seconds are called apneas.
- Sleep paralysis, characterized by temporary paralysis of the body shortly before or after sleep. Sleep paralysis may be accompanied by visual, auditory or tactile hallucinations. It is not a disorder unless severe, and is often seen as part of narcolepsy.
- Sleepwalking or somnambulism, engaging in activities normally associated with wakefulness (such as eating or dressing), which may include walking, without the conscious knowledge of the subject.
- Somniphobia, one cause of sleep deprivation, a dread/ fear of falling asleep or going to bed. Signs of the illness include anxiety and panic attacks before and during attempts to sleep.
- Dyssomnias – A broad category of sleep disorders characterized by either hypersomnia or insomnia. The three major subcategories include intrinsic (i.e., arising from within the body), extrinsic (secondary to environmental conditions or various pathologic conditions), and disturbances of circadian rhythm.
- Insomnia: Insomnia may be primary or it may be comorbid with or secondary to another disorder such as a mood disorder (i.e., emotional stress, anxiety, depression) or underlying health condition (i.e., asthma, diabetes, heart disease, pregnancy or neurological conditions).
- Primary hypersomnia: Hypersomnia of central or brain origin
- Narcolepsy: A chronic neurological disorder (or dyssomnia), which is caused by the brain's inability to control sleep and wakefulness.
- Idiopathic hypersomnia: A chronic neurological disease similar to narcolepsy, in which there is an increased amount of fatigue and sleep during the day. Patients who suffer from idiopathic hypersomnia cannot obtain a healthy amount of sleep for a regular day of activities. This hinders the patients' ability to perform well, and patients have to deal with this for the rest of their lives.
- Recurrent hypersomnia, including Kleine–Levin syndrome
- Post traumatic hypersomnia
- Menstrual-related hypersomnia
- Sleep disordered breathing (SDB), including (non-exhaustive):
- Restless leg syndrome
- Periodic limb movement disorder
- Circadian rhythm sleep disorders
- Parasomnias – A category of sleep disorders that involve abnormal and unnatural movements, behaviors, emotions, perceptions, and dreams in connection with sleep.
- Bedwetting or sleep enuresis
- Bruxism (Tooth-grinding)
- Catathrenia – nocturnal groaning
- Exploding head syndrome – Waking up in the night hearing loud noises.
- Sleep terror (or Pavor nocturnus) – Characterized by a sudden arousal from deep sleep with a scream or cry, accompanied by some behavioral manifestations of intense fear.
- REM sleep behavior disorder
- Sleepwalking (or somnambulism)
- Sleep talking (or somniloquy)
- Sleep sex (or sexsomnia)
- Medical or psychiatric conditions that may produce sleep disorders
- Sleeping sickness – a parasitic disease which can be transmitted by the Tsetse fly.
A systematic review found that traumatic childhood experiences (such as family conflict or sexual trauma) significantly increases the risk for a number of sleep disorders in adulthood, including sleep apnea, narcolepsy, and insomnia. It is currently unclear whether moderate alcohol consumption increases the risk of obstructive sleep apnea.
In addition, an evidence-based synopsis suggests that idiopathic REM sleep behavior disorder (iRBD) may have a hereditary component. A total of 632 participants, half with iRBD and half without, completed self-report questionnaires. The results of the study suggest that people with iRBD are more likely to report having a first-degree relative with the same sleep disorder than people of the same age and sex that do not have the disorder. More research needs to be conducted to further understand the hereditary nature of sleep disorders.
A population susceptible to the development of sleep disorders includes people who have experienced a traumatic brain injury (TBI). Because many researchers have focused on this issue, a systematic review was conducted to synthesize their findings. The results indicate that individuals who experienced a TBI are most disproportionately at risk for developing narcolepsy, obstructive sleep apnea, excessive daytime sleepiness, and insomnia. The study's complete findings can be found in the table below:
|Source of data||Sleep variable||Community||TBI||Community||TBI|
|Sleep problem||Sleep initiation||77||77||.05||.41||5.33||<.001|
|Excessive daytime sleepiness||85||99||.10||.24||2.65||.008|
|Obstructive sleep apnoea||1741||283||.02||.25||15.51||<.001|
|Periodic limb movements||18,980||212||.04||.08||2.95||.003|
|Excessive daytime sleepiness||16,583||651||.09||.27||15.27||<.001|
|Early morning awakening||24,600||364||.18||.38||9.76||<.001|
Sleep disorders and neurodegenerative diseases
Neurodegenerative diseases have often been associated with sleep disorders, mainly when they are characterized by abnormal accumulation of alpha-synuclein, such as multiple system atrophy (MSA), Parkinson's disease (PD) and Lewy body disease (LBD). For instance, people diagnosed with PD have often presented different kinds of sleep concerns, commonly in regard to insomnia (around 70% of the PD population), hypersomnia (more than 50% of the PD population), and REM sleep behavior disorder (RBD) - that may affect around 40% of the PD population and it is associated with increased motor symptoms. Furthermore, RBD has been highlighted as a strong precursor for future development of those neurodegenerative diseases over several years in prior, which seems to be a great opportunity for improving the treatments of the disease.
Sleep disturbances have been also observed in Alzheimer's disease (AD), affecting about 45% of its population. When based on caregiver reports, this percentage increases to about 70%. As well as in PD population, insomnia and hypersomnia are frequently recognized in AD patients, which have been associated with accumulation of beta-amyloid, circadian rhythm sleep disorders (CRSD) and melatonin alteration. Additionally, changes in sleep architecture are observed in AD. Although sleep architecture seems to naturally change with age, its development appears aggravated in AD patients. SWS potentially decreases (and is sometimes absent), spindles and the length of time spent in REM sleep are also reduced, while its latency increases. Poor sleep onset in AD has been associated with dream-related hallucination, increased restlessness, wandering and agitation that seem related to sundowning - a typical chronobiological phenomenon presented in the disease.
The neurodegenerative conditions are commonly related to structural brain impairment, which might disrupt the states of sleep and wakefulness, circadian rhythm, motor or non motor functioning. On the other hand, sleep disturbances are frequently related to worsening patient's cognitive functioning, emotional state and quality of life. Furthermore, these abnormal behavioral symptoms negatively contribute to overwhelming their relatives and caregivers. The limited research related to it and the increasing life expectancy calls for a deeper understanding of the relationship between sleep disorders and neurodegenerative disease.
Sleep disturbances and Alzheimer’s Disease
More than 70% of people with dementia are affected by Alzheimer's disease (AD). Despite this high number, our understanding of the underlying mechanisms for disease progression remains very limited. However, recent studies have highlighted a link between sleep disturbances and Alzheimer's disease.
Sleep changes with normal aging. Over time, a decrease in time sleeping and a decrease in the quantity of NREM sleep can be observed, specifically in NREM SWS (less than 10% of the SWS is maintained). Older people also are more prone to insomnia or sleep apnea.
In Alzheimer's disease, in addition to cognitive decline and memory impairment, there are also significant sleep disturbances with modified sleep architecture. The latter may consist in sleep fragmentation, reduced sleep duration, insomnia, increased daytime napping, decreased quantity of some sleep stages, and a growing resemblance between some sleep stages (N1 and N2). More than 65% of people with Alzheimer's disease suffer from this type of sleep disturbance.
One factor that could explain this change in sleep architecture is a change in circadian rhythm, which regulates sleep. A disruption of the circadian rhythm would generate sleep disturbances. Some studies show that people with AD have a delayed circadian rhythm, whereas in normal aging, an advanced circadian rhythm is present.
In addition to these psychological symptoms, at a neurological level there are two main symptoms of Alzheimer's disease. The first is an accumulation of beta-amyloid waste forming aggregate “plaques”. The second is an accumulation of tau protein.
It has been shown that the sleep-wake cycle acts on the beta-amyloid burden, which is a central component found in AD. As individuals awaken, the production of beta-amyloid protein will be more consistent than its production during sleep. This is explained by two phenomena. The first is that the metabolic activity will be higher during waking, thus resulting in greater secretion of beta-amyloid protein. The second is that oxidative stress will also increase, which leads to greater AB production.
On the other hand, it is during sleep that beta-amyloid residues are degraded to prevent plaque formation. The glymphatic system is responsible for this through the phenomenon of glymphatic clearance. Thus, during wakefulness, the AB burden is greater because the metabolic activity and oxidative stress are higher, and there is no protein degradation by the glymphatic clearance. During sleep, the burden is reduced as there is less metabolic activity and oxidative stress (in addition to the glymphatic clearance that occurs).
Glymphatic clearance occurs during the NREM SWS sleep. This sleep stage decreases in normal aging, resulting in less glymphatic clearance and increased AB burden that will form AB plaques. Therefore, sleep disturbances in individuals with AD will amplify this phenomenon.
The decrease in the quantity and quality of the NREM SWS, as well as the disturbances of sleep will therefore increase the AB plaques. This initially occurs in the hippocampus, which is a brain structure integral in long-term memory formation. Hippocampus cell death occurs, which contributes to diminished memory performance and cognitive decline found in AD.
Although the causal relationship is unclear, the development of AD correlates with the development of prominent sleep disorders. In the same way, sleep disorders exacerbate disease progression, forming a positive feedback relationship. As a result, sleep disturbances are no longer only a symptom of AD; the relationship between sleep disturbances and AD is bidirectional.
At the same time, it has been shown that memory consolidation in long-term memory (which depends on the hippocampus) occurs during NREM sleep. This indicates that a decrease in the NREM sleep will result in less consolidation, resulting in poorer memory performances in hippocampal-dependent long-term memory. This drop in performance is one of the central symptoms of AD.
Recent studies have also linked sleep disturbances, neurogenesis and AD. The subgranular zone and the subventricular zone continued to produce new neurons in adult brains. These new cells are then incorporated into neuronal circuits and the subragranular zone, which is found in the hippocampus. These new cells contribute to learning and memory, playing an essential role in hippocampal-dependent memory.
However, recent studies have shown that several factors can interrupt neurogenesis, including stress and prolonged sleep deprivation (more than one day). The sleep disturbances encountered in AD could therefore suppress neurogenesis—and thus impair hippocampal functions. This would contribute to diminished memory performances and the progression of AD, and the progression of AD would aggravate sleep disturbances.
Changes in sleep architecture found in patients with AD occur during the preclinical phase of AD. These changes could be used to detect those most at risk of developing AD. However, this is still only theoretical.
While the exact mechanisms and the causal relationship between sleep disturbances and AD remains unclear, these findings already provide a better understanding and offer possibilities to improve targeting of at-risk populations—and the implementation of treatments to curb the cognitive decline of AD patients.
Sleep disorder symptoms in psychiatric illnesses
In individuals with psychiatric illnesses, sleep disorders may include a variety of clinical symptoms such as excessive daytime sleepiness, difficulty falling asleep, difficulty staying asleep, nightmares, sleep talking, sleepwalking, and poor quality sleep, among many others. Sleep disturbances - insomnia, hypersomnia and delayed sleep-phase disorder - are quite prevalent in severe mental illnesses such as psychotic disorders. In those with schizophrenia, sleep disorders contribute to cognitive deficits in learning and memory. Sleep disturbances often occur before the onset of psychosis. Sleep deprivation can also produce hallucinations, delusions and depression. A 2019 study investigated the three above-mentioned sleep disturbances in schizophrenia-spectrum (SCZ) and bipolar (BP) disorders in 617 SCZ individuals, 440 BP individuals, and 173 healthy controls (HC). Sleep disturbances were identified using the Inventory for Depressive Symptoms - clinician rated scale (IDS-C). Results suggested that at least one type of sleep disturbance was reported in 78% of the SCZ population, in 69% individuals with BD, and in 39% of healthy controls. The SCZ group reported the most number of sleep disturbances compared to the BD and HC groups; specifically, hypersomnia was more frequent among individuals with SCZ, and delayed sleep phase disorder was three times more common in the SCZ group compared to the BD group. Insomnias were the most frequently reported sleep disturbance across all three groups.
One of the main behavioral symptoms of bipolar disorder is abnormal sleep. Studies have suggested that 23-78% of individuals with bipolar disorders consistently report symptoms of excessive time spent sleeping, or hypersomnia. The pathogenesis of bipolar disorder, including the higher risk of suicidal ideation, could possibly be linked to circadian rhythm variability, and sleep disturbances are a good predictor of mood swings. The most common sleep-related symptom of bipolar disorder is insomnia, in addition to hypersomnia, nightmares, poor sleep quality, OSA, extreme daytime sleepiness, etc. Moreover, animal models have shown that sleep debt can induce episodes of bipolar mania in laboratory mice, but these models are still limited in their potential to explain bipolar disease in humans with all its multifaceted symptoms, including those related to sleep disturbances.
Major depressive disorder (MDD)
Sleep disturbances (insomnia or hypersomnia) are not a necessary diagnostic criterion—but one of the most frequent symptoms of individuals with major depressive disorder (MDD). Among individuals with MDD, insomnia and hypersomnia have prevalence rates of 88% and 27%, respectively, whereas individuals with insomnia have a threefold increased risk of developing MDD. Depressed mood and sleep efficiency strongly co-vary, and while sleep regulation problems may precede depressive episodes, such depressive episodes may also precipitate sleep deprivation. Fatigue, as well as sleep disturbances such as irregular and excessive sleepiness, are linked to symptoms of depression. Recent research has even pointed to sleep problems and fatigues as potential driving forces bridging MDD symptoms to those of co-occurring generalized anxiety disorder.
Treatments for sleep disorders generally can be grouped into four categories:
- Behavioral and psychotherapeutic treatment
- Rehabilitation and management
- Other somatic treatment
None of these general approaches is sufficient for all patients with sleep disorders. Rather, the choice of a specific treatment depends on the patient's diagnosis, medical and psychiatric history, preferences, as well as the expertise of the treating clinician. Often, behavioral/psychotherapeutic and pharmacological approaches may be compatible, and can effectively be combined to maximize therapeutic benefits. Management of sleep disturbances that are secondary to mental, medical, or substance abuse disorders should focus on the underlying conditions.
Medications and somatic treatments may provide the most rapid symptomatic relief from some sleep disturbances. Certain disorders, such as narcolepsy, are best treated with prescription drugs such as modafinil. Others, such as chronic and primary insomnia, may be more amenable to behavioral interventions—with more durable results.
Chronic sleep disorders in childhood, which affect some 70% of children with developmental or psychological disorders, are under-reported and under-treated. Sleep-phase disruption is also common among adolescents, whose school schedules are often incompatible with their natural circadian rhythm. Effective treatment begins with careful diagnosis using sleep diaries and perhaps sleep studies. Modifications in sleep hygiene may resolve the problem, but medical treatment is often warranted.
Special equipment may be required for treatment of several disorders such as obstructive apnea, circadian rhythm disorders and bruxism. In severe cases, it may be necessary for individuals to accept living with the disorder, however well managed.
Some sleep disorders have been found to compromise glucose metabolism.
Histamine plays a role in wakefulness in the brain. An allergic reaction over produces histamine, causing wakefulness and inhibiting sleep. Sleep problems are common in people with allergic rhinitis. A study from the N.I.H. found that sleep is dramatically impaired by allergic symptoms, and that the degree of impairment is related to the severity of those symptoms. Treatment of allergies has also been shown to help sleep apnea.
A review of the evidence in 2012 concluded that current research is not rigorous enough to make recommendations around the use of acupuncture for insomnia. The pooled results of two trials on acupuncture showed a moderate likelihood that there may be some improvement to sleep quality for individuals with insomnia.: 15 This form of treatment for sleep disorders is generally studied in adults, rather than children. Further research would be needed to study the effects of acupuncture on sleep disorders in children.
Research suggests that hypnosis may be helpful in alleviating some types and manifestations of sleep disorders in some patients. "Acute and chronic insomnia often respond to relaxation and hypnotherapy approaches, along with sleep hygiene instructions." Hypnotherapy has also helped with nightmares and sleep terrors. There are several reports of successful use of hypnotherapy for parasomnias specifically for head and body rocking, bedwetting and sleepwalking.
Although more research should be done to increase the reliability of this method of treatment, research suggests that music therapy can improve sleep quality in acute and chronic sleep disorders. In one particular study, participants (18 years or older) who had experienced acute or chronic sleep disorders were put in a randomly controlled trial, and their sleep efficiency, in the form of overall time asleep, was observed. In order to assess sleep quality, researchers used subjective measures (i.e. questionnaires) and objective measures (i.e. polysomnography). The results of the study suggest that music therapy did improve sleep quality in subjects with acute or chronic sleep disorders, though only when tested subjectively. Although these results are not fully conclusive and more research should be conducted, it still provides evidence that music therapy can be an effective treatment for sleep disorders.
In another study specifically looking to help people with insomnia, similar results were seen. The participants that listened to music experienced better sleep quality than those who did not listen to music. Listening to slower pace music before bed can help decrease the heart rate, making it easier to transition into sleep. Studies have indicated that music helps induce a state of relaxation that shifts an individual's internal clock towards the sleep cycle. This is said to have an effect on children and adults with various cases of sleep disorders. Music is most effective before bed once the brain has been conditioned to it, helping to achieve sleep much faster.
Research suggests that melatonin is useful in helping people fall asleep faster (decreased sleep latency), to stay asleep longer, and to experience improved sleep quality. To test this, a study was conducted that compared subjects who had taken melatonin to subjects with primary sleep disorders who had taken a placebo. Researchers assessed sleep onset latency, total minutes slept, and overall sleep quality in the melatonin and placebo groups to note the differences. In the end, researchers found that melatonin decreased sleep onset latency and increased total sleep time  but had an insignificant and inconclusive impact on the quality of sleep compared to a placebo group.
Due to rapidly increasing knowledge about sleep in the 20th century, including the discovery of REM sleep in the 1950s and circadian rhythm disorders in the 70s and 80s, the medical importance of sleep was recognized. The medical community began paying more attention than previously to primary sleep disorders, such as sleep apnea, as well as the role and quality of sleep in other conditions. By the 1970s in the US, clinics and laboratories devoted to the study of sleep and sleep disorders had been founded, and a need for standards arose.
Specialists in sleep medicine were originally certified by the American Board of Sleep Medicine, which still recognizes specialists. Those passing the Sleep Medicine Specialty Exam received the designation "diplomate of the ABSM." Sleep medicine is now a recognized subspecialty within internal medicine, family medicine, pediatrics, otolaryngology, psychiatry and neurology in the United States. Certification in Sleep medicine shows that the specialist:
"has demonstrated expertise in the diagnosis and management of clinical conditions that occur during sleep, that disturb sleep, or that are affected by disturbances in the wake-sleep cycle. This specialist is skilled in the analysis and interpretation of comprehensive polysomnography, and well-versed in emerging research and management of a sleep laboratory."
Competence in sleep medicine requires an understanding of a myriad of very diverse disorders, many of which present with similar symptoms such as excessive daytime sleepiness, which, in the absence of volitional sleep deprivation, "is almost inevitably caused by an identifiable and treatable sleep disorder", such as sleep apnea, narcolepsy, idiopathic hypersomnia, Kleine–Levin syndrome, menstrual-related hypersomnia, idiopathic recurrent stupor, or circadian rhythm disturbances. Another common complaint is insomnia, a set of symptoms which can have a great many different causes, physical and mental. Management in the varying situations differs greatly and cannot be undertaken without a correct diagnosis.
Sleep dentistry (bruxism, snoring and sleep apnea), while not recognized as one of the nine dental specialties, qualifies for board-certification by the American Board of Dental Sleep Medicine (ABDSM). The resulting diplomate status is recognized by the American Academy of Sleep Medicine (AASM), and these dentists are organized in the Academy of Dental Sleep Medicine (USA). The qualified dentists collaborate with sleep physicians at accredited sleep centers, and can provide oral appliance therapy and upper airway surgery to treat or manage sleep-related breathing disorders.
Occupational therapy is an area of medicine that can also address a diagnosis of sleep disorder, as rest and sleep is listed in the Occupational Therapy Practice Framework (OTPF) as its own occupation of daily living. Rest and sleep is described as restorative in order to support engagement in other occupational therapy occupations. In the OTPF, the occupation of rest and sleep is broken down into rest, sleep preparation and sleep participation. Occupational therapists have been shown to help improve restorative sleep through the use of assistive devices/equipment, cognitive behavioral therapy for Insomnia, therapeutic activities, and/or lifestyle interventions.
In the UK, knowledge of sleep medicine and possibilities for diagnosis and treatment seem to lag. The Guardian quotes the director of the Imperial College Healthcare Sleep Center: "One problem is that there has been relatively little training in sleep medicine in this country – certainly there is no structured training for sleep physicians." The Imperial College Healthcare shows attention to obstructive sleep apnea syndrome (OSA) and very few other sleep disorders. Some NHS trusts have specialist clinics for respiratory and/or neurological sleep medicine.
Children and young adults
According to one meta-analysis of sleep disorders in children, confusional arousals and sleepwalking are the two most common sleep disorders among children. An estimated 17.3% of kids between 3 and 13 years old experience confusional arousals. About 17% of children sleepwalk, with the disorder being more common among boys than girls. The peak ages of sleepwalking are from 8 to 12 years old. A different systematic review offers a high range of prevalence rates of sleep bruxism for children. Parasomnias like sleepwalking and talking typically occur during the first part of an individual's sleep cycle, which is known as the first slow wave of sleep  During this period of the sleep cycle your mind and body slows down causing you to feel drowsy and relaxed. At this stage it is the easiest for you to wake up, therefore many children do not remember what happened during this time. Nightmares are also considered another parasomnia among children, where they typically remember what took place. However, nightmares only occur during the last stage of sleep known as Rapid Eye Movement (REM) sleep. This is the deepest stage of sleep, it is known as REM because an individual can show a host of neurological and physiological responses which are similar to being awake.
Between 15.29% and 38.6% of preschoolers grind their teeth at least one night a week. All but one of the included studies reports decreasing bruxist prevalence as age increased, as well as a higher prevalence among boys than girls. By adulthood, parasomnias normally can be resolved due to a person's growth, however there is 4% of people have recurring symptoms.
Another systematic review noted 7-16% of young adults suffer from delayed sleep phase disorder. This disorder reaches peak prevalence when people are in their 20s. Between 20 and 26% of adolescents report a sleep onset latency of greater than 30 minutes. Also, 7-36% have difficulty initiating sleep. Asian teens tend to have a higher prevalence of all of these adverse sleep outcomes—than their North American and European counterparts.
Insomnia is a prevalent form of sleep deprivation. You may have problems getting asleep, staying asleep, or both if you have it. As a result, you may receive insufficient sleep or sleep of poor quality. When you wake up, you might not feel refreshed. Combining results from 17 studies on insomnia in China, a pooled prevalence of 15.0% is reported for the country. This is considerably lower than a series of Western countries (50.5% in Poland, 37.2% in France and Italy, 27.1% in USA). However, the result is consistent among other East Asian countries. Men and women residing in China experience insomnia at similar rates. A separate meta-analysis focusing on this sleeping disorder in the elderly mentions that those with more than one physical or psychiatric malady experience it at a 60% higher rate than those with one condition or less. It also notes a higher prevalence of insomnia in women over the age of 50 than their male counterparts.
A study that was resulted from a collaboration between Massachusetts General Hospital and Merck describes the development of an algorithm to identify patients with sleep disorders using electronic medical records. The algorithm that incorporated a combination of structured and unstructured variables identified more than 36,000 individuals with physician-documented insomnia.
Obstructive sleep apnea
Obstructive sleep apnea (OSA) affects around 4% of men and 2% of women in the United States. In general, this disorder is more prevalent among men. However, this difference tends to diminish with age. Women experience the highest risk for OSA during pregnancy. Also, they tend to report experiencing depression and insomnia in conjunction with obstructive sleep apnea. In a meta-analysis of the various Asian countries, India and China present the highest prevalence of the disorder. Specifically, about 13.7% of the Indian population and 7% of Hong Kong's population is estimated to have OSA. The two groups experience daytime OSA symptoms such as difficulties concentrating, mood swings, or high blood pressure, at similar rates (prevalence of 3.5% and 3.57%, respectively).
A systematic review states 7.6% of the general population experiences sleep paralysis at least once in their lifetime. Its prevalence among men is 15.9%, while 18.9% of women experience it. When considering specific populations, 28.3% of students and 31.9% of psychiatric patients have experienced this phenomenon at least once in their lifetime. Of those psychiatric patients, 34.6% have panic disorder. Sleep paralysis in students is slightly more prevalent for those of Asian descent (39.9%) than other ethnicities (Hispanic: 34.5%, African descent: 31.4%, Caucasian 30.8%).
Restless leg syndrome
According to one meta-analysis, the mean prevalence rate for North America and Western Europe is estimated to be 14.5±8.0%. Specifically in the United States, the prevalence of restless leg syndrome is estimated to be between 5% and 15.7% when using strict diagnostic criteria. RLS is over 35% more prevalent in American women than their male counterparts.
- Hirshkowitz M (2004). "Chapter 10, Neuropsychiatric Aspects of Sleep and Sleep Disorders (pp 315-340)" (Google Books preview includes entire chapter 10). In Yudofsky SC, Hales RE (eds.). Essentials of neuropsychiatry and clinical neurosciences (4 ed.). Arlington, Virginia, USA: American Psychiatric Publishing. ISBN 978-1-58562-005-0.
...insomnia is a symptom. It is neither a disease nor a specific condition. (from p. 322)
- "APA "What are sleep disorders?", Retrieved 2019-06-25".
- "Sleep Problems and Sleep Disorders". Sleepify. Retrieved 2021-08-24.
- Meltzer LJ, Johnson C, Crosette J, Ramos M, Mindell JA (June 2010). "Prevalence of diagnosed sleep disorders in pediatric primary care practices". Pediatrics. 125 (6): e1410-8. doi:10.1542/peds.2009-2725. PMC 3089951. PMID 20457689.
- Roepke, S. K., & Ancoli-Israel, S. (2010). Sleep disorders in the elderly. The Indian Journal of Medical Research, 131, 302–310.
- American Academy of Sleep Medicine (2001). The International Classification of Sleep Disorders, Revised (ICSD-R) (PDF). ISBN 978-0-9657220-1-8. Archived from the original (PDF) on 2011-07-26.
- "Idiopathic hypersomnia | Genetic and Rare Diseases Information Center (GARD) – an NCATS Program".
- Arnulf I, Rico TJ, Mignot E (October 2012). "Diagnosis, disease course, and management of patients with Kleine-Levin syndrome". The Lancet. Neurology. 11 (10): 918–28. doi:10.1016/S1474-4422(12)70187-4. PMID 22995695. S2CID 7636103.
- "Narcolepsy Fact Sheet". Retrieved 2011-06-23.
- Hockenbury DH, Hockenbury SE (2010). Discovering psychology (5th ed.). New York, NY: Worth Publishers. p. 157. ISBN 978-1-4292-1650-0.
- "Nocturia or Frequent Urination at Night". Sleep Foundation. November 21, 2018.
- "REM Sleep Behavior Disorder". Mayo Clinic. Retrieved 27 July 2016.
- Mandell R. "Snoring: A Precursor to Medical Issues" (PDF). Stop Snoring Device. Retrieved 27 July 2016.
- "Sleep Apnea Diagnosis". SingularSleep. Retrieved 27 April 2018.
- MeSH 68020920
- Levin Noy, Shir. "Insomnia treatment". hiburimnamal.co.il.
- Smith MA, Robinson L, Boose G, Segal R (September 2011). "Sleep Disorders and Sleeping Problems". Archived from the original on 2011-12-05. Cite journal requires
- National Institute of Neurological Disorders and Stroke (June 27, 2011). "NINDS Narcolepsy". Archived from the original on February 21, 2014. Cite journal requires
- Voderholzer U, Guilleminault C (2012). "Sleep disorders". Neurobiology of Psychiatric Disorders. Handbook of Clinical Neurology. 106. pp. 527–40. doi:10.1016/B978-0-444-52002-9.00031-0. ISBN 978-0-444-52002-9. PMID 22608642.
- Thorpy, Michael J. "PARASOMNIACS." The International Classification of Sleep Disorders: Diagnostic and Coding Manual. Rochester: American Sleep Disorders Association, 1990. Print.
- Kajeepeta S, Gelaye B, Jackson CL, Williams MA (March 2015). "Adverse childhood experiences are associated with adult sleep disorders: a systematic review". Sleep Medicine. 16 (3): 320–30. doi:10.1016/j.sleep.2014.12.013. PMC 4635027. PMID 25777485.
- UTHSCSA Dental School CATs Author. "UTCAT2395, Found CAT view, CRITICALLY APPRAISED TOPICs". cats.uthscsa.edu. Retrieved 2016-03-08.
- Schenck CH (November 2013). "Family history of REM sleep behavior disorder more common in individuals affected by the disorder than among unaffected individuals". Evidence-Based Mental Health. 16 (4): 114. doi:10.1136/eb-2013-101479. PMID 23970760. S2CID 2218369.
- Mathias JL, Alvaro PK (August 2012). "Prevalence of sleep disturbances, disorders, and problems following traumatic brain injury: a meta-analysis". Sleep Medicine. 13 (7): 898–905. doi:10.1016/j.sleep.2012.04.006. PMID 22705246.
- Aurora, R., Zak, R., Maganti, R., Auerbach, S., Casey, K., Chowdhuri, S., . . . Morgenthaler, T. (2010). Best practice guide for the treatment of REM sleep behavior disorder (RBD). Journal of Clinical Sleep Medicine : JCSM : Official Publication of the American Academy of Sleep Medicine, 6(1), 85-95.
- Zhong, Naismith, Rogers, & Lewis. (2011). Sleep–wake disturbances in common neurodegenerative diseases: A closer look at selected aspects of the neural circuitry. Journal of the Neurological Sciences, 307(1-2), 9-14.
- Bjørnarå, Dietrichs, & Toft. (2013). REM sleep behavior disorder in Parkinson's disease – Is there a gender difference? Parkinsonism and Related Disorders, 19(1), 120-122.
- Malkani, R., & Attarian, H. (2015). Sleep in Neurodegenerative Disorders. Current Sleep Medicine Reports, 1(2), 81-90.
- Bjørnarå, K., Dietrichs, E., & Toft, M. (2015). Longitudinal assessment of probable rapid eye movement sleep behavior disorder in Parkinson's disease. European Journal of Neurology, 22(8), 1242-1244.
- Wang, P., Wing, Y.K., Xing, J. et al. Aging Clin Exp Res (2016) 28: 951. https://doi.org/10.1007/s40520-015-0382-8
- McCarter, S., & Howell, J. (2017). REM Sleep Behavior Disorder and Other Sleep Disturbances in Non-Alzheimer Dementias. Current Sleep Medicine Reports, 3(3), 193-203.
- Dick-Muehlke, C. (2015). Psychosocial studies of the individual's changing perspectives in Alzheimer's disease (Premier Reference Source). Hershey, PA: Medical Information Science Reference.
- Kent BA, Mistlberger RE (April 2017). "Sleep and hippocampal neurogenesis: Implications for Alzheimer's disease". Frontiers in Neuroendocrinology. 45: 35–52. doi:10.1016/j.yfrne.2017.02.004. PMID 28249715. S2CID 39928206.
- Mander BA, Winer JR, Jagust WJ, Walker MP (August 2016). "Sleep: A Novel Mechanistic Pathway, Biomarker, and Treatment Target in the Pathology of Alzheimer's Disease?". Trends in Neurosciences. 39 (8): 552–566. doi:10.1016/j.tins.2016.05.002. PMC 4967375. PMID 27325209.
- Tranah GJ, Blackwell T, Stone KL, Ancoli-Israel S, Paudel ML, Ensrud KE, et al. (November 2011). "Circadian activity rhythms and risk of incident dementia and mild cognitive impairment in older women". Annals of Neurology. 70 (5): 722–32. doi:10.1002/ana.22468. PMC 3244839. PMID 22162057.
- Xie L, Kang H, Xu Q, Chen MJ, Liao Y, Thiyagarajan M, et al. (October 2013). "Sleep drives metabolite clearance from the adult brain". Science. 342 (6156): 373–7. Bibcode:2013Sci...342..373X. doi:10.1126/science.1241224. PMC 3880190. PMID 24136970.
- Diekelmann S, Born J (February 2010). "The memory function of sleep". Nature Reviews. Neuroscience. 11 (2): 114–26. doi:10.1038/nrn2762. PMID 20046194. S2CID 1851910.
- Meerlo P, Mistlberger RE, Jacobs BL, Heller HC, McGinty D (June 2009). "New neurons in the adult brain: the role of sleep and consequences of sleep loss". Sleep Medicine Reviews. 13 (3): 187–94. doi:10.1016/j.smrv.2008.07.004. PMC 2771197. PMID 18848476.
- Hombali A, Seow E, Yuan Q, Chang SH, Satghare P, Kumar S, et al. (September 2019). "Prevalence and correlates of sleep disorder symptoms in psychiatric disorders". Psychiatry Research. 279: 116–122. doi:10.1016/j.psychres.2018.07.009. PMID 30072039.
- Laskemoen JF, Simonsen C, Büchmann C, Barrett EA, Bjella T, Lagerberg TV, et al. (May 2019). "Sleep disturbances in schizophrenia spectrum and bipolar disorders - a transdiagnostic perspective". Comprehensive Psychiatry. 91: 6–12. doi:10.1016/j.comppsych.2019.02.006. PMID 30856497.
- Pocivavsek A, Rowland LM (January 2018). "Basic Neuroscience Illuminates Causal Relationship Between Sleep and Memory: Translating to Schizophrenia". Schizophrenia Bulletin. 44 (1): 7–14. doi:10.1093/schbul/sbx151. PMC 5768044. PMID 29136236.
- Steardo L, de Filippis R, Carbone EA, Segura-Garcia C, Verkhratsky A, De Fazio P (2019-07-18). "Sleep Disturbance in Bipolar Disorder: Neuroglia and Circadian Rhythms". Frontiers in Psychiatry. 10: 501. doi:10.3389/fpsyt.2019.00501. PMC 6656854. PMID 31379620.
- Logan RW, McClung CA (May 2016). "Animal models of bipolar mania: The past, present and future". Neuroscience. 321: 163–188. doi:10.1016/j.neuroscience.2015.08.041. PMC 4766066. PMID 26314632.
- Liu X, Buysse DJ, Gentzler AL, Kiss E, Mayer L, Kapornai K, et al. (January 2007). "Insomnia and hypersomnia associated with depressive phenomenology and comorbidity in childhood depression". Sleep. 30 (1): 83–90. doi:10.1093/sleep/30.1.83. PMID 17310868.
- Murphy MJ, Peterson MJ (March 2015). "Sleep Disturbances in Depression". Sleep Medicine Clinics. 10 (1): 17–23. doi:10.1016/j.jsmc.2014.11.009. PMC 5678925. PMID 26055669.
- Coussement, C.; Heeren, A. (2022). "Sleep problems as a transdiagnostic hub bridging impaired attention control, generalized anxiety, and depression". Journal of Affective Disorders. 296: 305–308. doi:10.1016/j.jad.2021.09.092.
- Ramar K, Olson EJ (August 2013). "Management of common sleep disorders". American Family Physician. 88 (4): 231–8. PMID 23944726.
- Ivanenko A, Massey C (October 1, 2006). "Assessment and Management of Sleep Disorders in Children". Psychiatric Times. 23 (11).
- Keckeis M, Lattova Z, Maurovich-Horvat E, Beitinger PA, Birkmann S, Lauer CJ, et al. (March 2010). Finkelstein D (ed.). "Impaired glucose tolerance in sleep disorders". PLOS ONE. 5 (3): e9444. Bibcode:2010PLoSO...5.9444K. doi:10.1371/journal.pone.0009444. PMC 2830474. PMID 20209158.
- Thakkar MM (February 2011). "Histamine in the regulation of wakefulness". Sleep Medicine Reviews. 15 (1): 65–74. doi:10.1016/j.smrv.2010.06.004. PMC 3016451. PMID 20851648.
- Léger, Damien; Annesi-Maesano, Isabella; Carat, Francois; Rugina, Michel; Chanal, Isabelle; Pribil, Céline; El Hasnaoui, Abdelkader; Bousquet, Jean (2006-09-18). "Allergic rhinitis and its consequences on quality of sleep: An unexplored area". Archives of Internal Medicine. 166 (16): 1744–1748. doi:10.1001/archinte.166.16.1744. ISSN 0003-9926. PMID 16983053.
- "Allergies and Sleep". sleepfoundation.org. Retrieved 2017-06-08.
- Staevska MT, Mandajieva MA, Dimitrov VD (May 2004). "Rhinitis and sleep apnea". Current Allergy and Asthma Reports. 4 (3): 193–9. doi:10.1007/s11882-004-0026-0. PMID 15056401. S2CID 42447055.
- Cheuk DK, Yeung WF, Chung KF, Wong V (September 2012). "Acupuncture for insomnia". The Cochrane Database of Systematic Reviews. 9 (9): CD005472. doi:10.1002/14651858.cd005472.pub3. PMID 22972087.
- Stradling J, Roberts D, Wilson A, Lovelock F (March 1998). "Controlled trial of hypnotherapy for weight loss in patients with obstructive sleep apnoea". International Journal of Obesity and Related Metabolic Disorders. 22 (3): 278–81. doi:10.1038/sj.ijo.0800578. PMID 9539198.
- Ng BY, Lee TS (August 2008). "Hypnotherapy for sleep disorders" (PDF). Annals of the Academy of Medicine, Singapore. 37 (8): 683–8. PMID 18797562.
- Graci GM, Hardie JC (July 2007). "Evidenced-based hypnotherapy for the management of sleep disorders". The International Journal of Clinical and Experimental Hypnosis. 55 (3): 288–302. doi:10.1080/00207140701338662. PMID 17558719. S2CID 21598789.
- Hauri PJ, Silber MH, Boeve BF (June 2007). "The treatment of parasomnias with hypnosis: a 5-year follow-up study". Journal of Clinical Sleep Medicine. 3 (4): 369–73. doi:10.5664/jcsm.26858. PMC 1978312. PMID 17694725.
- Hurwitz TD, Mahowald MW, Schenck CH, Schluter JL, Bundlie SR (April 1991). "A retrospective outcome study and review of hypnosis as treatment of adults with sleepwalking and sleep terror". The Journal of Nervous and Mental Disease. 179 (4): 228–33. doi:10.1097/00005053-199104000-00009. PMID 2007894. S2CID 10018843.
- Owens LJ, France KG, Wiggs L (December 1999). "REVIEW ARTICLE: Behavioral and cognitive-behavioral interventions for sleep disorders in infants and children: A review". Sleep Medicine Reviews. 3 (4): 281–302. doi:10.1053/smrv.1999.0082. PMID 12531150.
- Wang CF, Sun YL, Zang HX (January 2014). "Music therapy improves sleep quality in acute and chronic sleep disorders: a meta-analysis of 10 randomized studies". International Journal of Nursing Studies. 51 (1): 51–62. doi:10.1016/j.ijnurstu.2013.03.008. PMID 23582682.
- Jespersen KV, Koenig J, Jennum P, Vuust P (August 2015). "Music for insomnia in adults". The Cochrane Database of Systematic Reviews (8): CD010459. doi:10.1002/14651858.cd010459.pub2. PMID 26270746.
- "Can Music Help Me Sleep?". WebMD. Retrieved 2019-09-29.
- Evernote (2018-07-26). "Can Music Make You a Productivity Powerhouse?". Medium. Retrieved 2019-09-29.
- "The Many Health and Sleep Benefits Of Music". Psychology Today. Retrieved 2019-09-30.
- Ferracioli-Oda E, Qawasmi A, Bloch MH (2013-06-06). "Meta-analysis: melatonin for the treatment of primary sleep disorders". PLOS ONE. 8 (5): e63773. Bibcode:2013PLoSO...863773F. doi:10.1371/journal.pone.0063773. PMC 3656905. PMID 23691095.
- "Meta-analysis: melatonin for the treatment of primary sleep disorders". www.crd.york.ac.uk. Retrieved 2016-03-08.
- "American Board of Medical Specialties : Recognized Physician Specialty and Subspecialty Certificates". Archived from the original on 2012-05-08. Retrieved 2008-07-21.
- Mahowald MW (March 2000). "What is causing excessive daytime sleepiness? Evaluation to distinguish sleep deprivation from sleep disorders". Postgraduate Medicine. 107 (3): 108–10, 115–8, 123. doi:10.3810/pgm.2000.03.932. PMID 10728139. S2CID 42939232.
- Araújo, Taís; Jarrin, Denise C.; Leanza, Yvan; Vallières, Annie; Morin, Charles M. (2017-02-01). "Qualitative studies of insomnia: Current state of knowledge in the field". Sleep Medicine Reviews. 31: 58–69. doi:10.1016/j.smrv.2016.01.003. ISSN 1087-0792. PMC 4945477. PMID 27090821.
- "About AADSM". Academy of Dental Sleep Medicine. 2008. Retrieved 2008-07-22.
- "About the ADBSM". American Board of Dental Sleep Medicine. Retrieved 2008-07-22.
- "Occupational Therapy Practice Framework: Domain and Process—Fourth Edition". American Journal of Occupational Therapy. 74 (Supplement_2): 7412410010p1. 2020-08-31. doi:10.5014/ajot.2020.74S2001. ISSN 0272-9490. S2CID 204057541.
- Ho EC, Siu AM (2018-07-29). "Occupational Therapy Practice in Sleep Management: A Review of Conceptual Models and Research Evidence". Occupational Therapy International. 2018: 8637498. doi:10.1155/2018/8637498. PMC 6087566. PMID 30150906.
- Wollenberg A (July 28, 2008). "Time to wake up to sleep disorders". Guardian News and Media Limited. Retrieved 2008-08-03.
- "Sleep services". Imperial College Healthcare NHS Trust. 2008. Archived from the original on 2008-10-04. Retrieved 2008-08-02.
- Carter KA, Hathaway NE, Lettieri CF (March 2014). "Common sleep disorders in children". American Family Physician. 89 (5): 368–77. PMID 24695508.
- Carter, Kevin A.; Hathaway, Nathanael E.; Lettieri, Christine F. (2014-03-01). "Common sleep disorders in children". American Family Physician. 89 (5): 368–377. ISSN 1532-0650. PMID 24695508.
- Patel, Aakash K.; Reddy, Vamsi; Araujo, John F. (2021), "Physiology, Sleep Stages", StatPearls, Treasure Island (FL): StatPearls Publishing, PMID 30252388, retrieved 2021-09-19
- Machado E, Dal-Fabbro C, Cunali PA, Kaizer OB (2014). "Prevalence of sleep bruxism in children: a systematic review". Dental Press Journal of Orthodontics. 19 (6): 54–61. doi:10.1590/2176-9451.19.6.054-061.oar. PMC 4347411. PMID 25628080.
- Gradisar M, Gardner G, Dohnt H (February 2011). "Recent worldwide sleep patterns and problems during adolescence: a review and meta-analysis of age, region, and sleep". Sleep Medicine. 12 (2): 110–8. doi:10.1016/j.sleep.2010.11.008. PMID 21257344.
- Cao XL, Wang SB, Zhong BL, Zhang L, Ungvari GS, Ng CH, et al. (2017-02-24). "The prevalence of insomnia in the general population in China: A meta-analysis". PLOS ONE. 12 (2): e0170772. Bibcode:2017PLoSO..1270772C. doi:10.1371/journal.pone.0170772. PMC 5325204. PMID 28234940.
- Rodriguez JC, Dzierzewski JM, Alessi CA (March 2015). "Sleep problems in the elderly". The Medical Clinics of North America. 99 (2): 431–9. doi:10.1016/j.mcna.2014.11.013. PMC 4406253. PMID 25700593.
- Kartoun U, Aggarwal R, Beam AL, Pai JK, Chatterjee AK, Fitzgerald TP, et al. (May 2018). "Development of an Algorithm to Identify Patients with Physician-Documented Insomnia". Scientific Reports. 8 (1): 7862. Bibcode:2018NatSR...8.7862K. doi:10.1038/s41598-018-25312-z. PMC 5959894. PMID 29777125.
- Mirrakhimov AE, Sooronbaev T, Mirrakhimov EM (February 2013). "Prevalence of obstructive sleep apnea in Asian adults: a systematic review of the literature". BMC Pulmonary Medicine. 13: 10. doi:10.1186/1471-2466-13-10. PMC 3585751. PMID 23433391.
- Wimms A, Woehrle H, Ketheeswaran S, Ramanan D, Armitstead J (2016). "Obstructive Sleep Apnea in Women: Specific Issues and Interventions". BioMed Research International. 2016: 1764837. doi:10.1155/2016/1764837. PMC 5028797. PMID 27699167.
- Valipour A (October 2012). "Gender-related differences in the obstructive sleep apnea syndrome". Pneumologie. 66 (10): 584–8. doi:10.1055/s-0032-1325664. PMID 22987326.
- "Obstructive sleep apnea – Symptoms and causes – Mayo Clinic". www.mayoclinic.org. Retrieved 2017-11-27.
- Sharpless BA, Barber JP (October 2011). "Lifetime prevalence rates of sleep paralysis: a systematic review". Sleep Medicine Reviews. 15 (5): 311–5. doi:10.1016/j.smrv.2011.01.007. PMC 3156892. PMID 21571556.
- Innes KE, Selfe TK, Agarwal P (August 2011). "Prevalence of restless legs syndrome in North American and Western European populations: a systematic review". Sleep Medicine. 12 (7): 623–34. doi:10.1016/j.sleep.2010.12.018. PMC 4634567. PMID 21752711.