Sleep Disorder Classification

Classification of Sleep Disorders

Physicians are involved in the diagnosis and treatment of sleep disorders. They bear the responsibility of diagnosing sleep-disordered breathing, insomnia, and sleep movement disorders. Dentist collaborate with physicians in recognizing various sleep disorders signs and symptoms during dental visits. Furthermore, sleep trained dentist can manage snoring and sleep-disordered breathing with oral appliances. Psychologists and other health care professionals can also diagnosis sleep insomnia, sleep-rhythm related problems, and other sleep disorders. These problems frequently occur in patients with chronic pain and sleep disordered breathing.

The areas of expertise of dentists in sleep medicine include clinical assessments, oral and airway examination, dental screening for airway issues, differential diagnosis and referral of patients for a sleep test or to a sleep physician. After a diagnosis has been made dentist can:

  • Offer sleep hygiene advice
  • Provide oral appliances
  • Refer patients for orthodontic treatment or maxillofacial surgery
  • Supervise and control comorbid orofacial problems (eg, bruxism, orofacial pain, sleep-related xerostomia)
  • Refer patients for sleep laboratory follow-up to monitor the efficacy of an oral appliances.

Many sleep disorders can occur at the same time. For example, at least one-third of patients with bruxism in the general population may also have sleep-disordered breathing conditions such as morning headache, obstructive sleep apnea, and periodic limb movements during sleep. Emerging data also suggest that rate of obstructive sleep apnea may be elevated (approximately 30%) in patients with temporomandibular disorders (TMDs) and other related pain disorders such as fibromyalgia (chronic widespread pain) This new data is remarkable because the traditional demographic and risk factors associated with sleep apnea, including male sex, older age, and high body mas index, are not commonly associated with TMDs. Thus, many physicians may not refer patients with TMDs for a sleep test. In the presence of comorbidities, dentist should request a consultation with sleep medicine experts.

Sound-Related Complaints


Snoring is the vibration of respiratory structures and the resulting sound due to obstructed air movement during breathing while sleeping. This commonly occurring loud sound is reported by the patient’s sleep partner or family. Snoring is generated at the level of the upper airway. It is associated with the vibration of the soft palate and the restriction of air passage with noisy air turbulence. About 40% of men and 24% of women are aware of snoring sounds as reported by a sleep partner. The occurrence of snoring tends to increase threefold during pregnancy. Patients who snore are reported to be at greater risk of cardiovascular disease (eg, hypertension) especially if snoring is associated with obstructive sleep apnea.

A sleep medicine consultation should mandatory for patients who report snoring in conjunction with daytime sleepiness, hypertension, cardiovascular problems, sleep disruption, insomnia, unrefreshing sleep, or consistently impaired concentration. The differential diagnosis of snoring includes obstructive sleep apnea-hypopnea, upper airway resistance, laryngospasm, and sleep talking.

Sleep apnea-hypopnea

An apnea is defined as a cessation of breathing for 10 seconds or more. There are two types of apnea (1) obstructive sleep apnea (most common), resulting from the presence of an obstruction in the upper airways; and (2) central sleep apnea, demonstrated by the absence of respiratory efforts (no chest movements) resulting from reduced signals from the brain to drive inspiration and expiration. Both kinds of apnea can be present simultaneously.

Hypopnea is most commonly defined as 1. a decrease in airflow of more than 50% 2. a decrease of more than 30% that is associated with oxyhemoglobin desaturation (of greater than 3% or 4%) or 3. an electroencephalographic arousal (sometimes referred to as a respiratory event-related arousal). Hypopnea is detected in both light sleep (stage 2) and rapid eye movement (REM) sleep, also called stage 5 sleep, paradoxical sleep, or active sleep.

The severity of sleep apnea is commonly defined as the number of apneas or hypopneas per hour of sleep, graded with the apneas-hypopnea index (AHI): 5 to 14 is considered mild; 15 to 30 is considered moderate; and more than 30 is considered sever.

Sleep apnea-hypopnea syndrome is defined as an AHI of 5 or more per hour of sleep and either excessive daytime sleepiness (as rated by questionnaires such as the Epworth sleepiness scale) or at least two of the following symptoms: recurrent awakening from sleep, choking, unrefreshing sleep, daytime fatigue, or impaired concentration.

According to the ground-breaking Wisconsin Sleep Cohort study, the prevalence of an AHI greater than 5 per hour among people aged 30 to 60 years old is 24% for men and 9% for women. Within this population, sleep apnea syndrome is found in 4% of middle-aged men and 2% of middle-aged women. When the rising prevalence of obesity is considered, updated estimates suggest that 17% of adults have at least mild obstructive sleep apnea (AHI of 15 or more per hour)

Patients with untreated sleep apnea may have a sevenfold greater risk of car accidents (drowsy driving) than do matched controls. Repeated oxyhemoglobin desaturation (up to 100 drops per hour of sleep) and sudden transient awakenings caused by sleep apnea also induce a significant level of physiologic stress in the patients, which is thought to be responsible for an increased risk of cardiovascular disease such as stroke, hypertension, or myocardial infraction.

Dentist’s clinical examination should include documentation of the main risk factors for obstructive sleep apnea: obesity, male sex, nasal obstruction, large tonsils, menopause, large tongue base, and narrow upper airway, or high-arched palate. Patients with TMDs, who are predominately women during child-bearing years, may also be at increased risk for obstructive sleep apnea. Alcohol consumption and sedatives such as benzodiazepines also contribute to upper airway obstruction by relaxing upper airway dilator muscles. Conditions that contribute to obstructive sleep apnea include: rhinitis (irritation and inflammation of the mucous membrane inside the nose), nasal congestion, and smoking.

In children, obstructive sleep apnea is usually related to enlarged tonsils and/or adenoids. Furthermore, in children, sleep apnea can be associated with an inward movement of the rib cage (paradoxical breathing), morning headaches, enuresis, slow growth rate, excessive daytime sleepiness, poor school performance, hyperactivity, or aggressive behavior. In the presence of the above findings, the threshold for diagnosing sleep apnea in children is low: An AHI of 1 or more per hour is considered abnormal.

Considering the life-threatening consequences of sleep apnea, dentists should refer patients suspected of having the syndrome to have a sleep test that is read by a board-certified sleep physician.

Sleepiness is a key element to investigate in the differential diagnosis. Sleepiness may be secondary to insomnia, narcolepsy, or periodic limb movement disorder.

In some patients, gastroesophageal reflux disease (GERD) is concomitant with sleep apnea-hypopnea. Thus, it is therefore important to exclude respiratory disorders in those patients who consult their dentist primarily about the problem of tooth damage caused by GERD.

Sleep bruxism

Sleep bruxism (tooth grinding) is a repetitive activity (repeated at least 3 times per episode) in the jaw muscles that generates tooth grinding sounds and occasional jaw clenching (a sustained muscle contraction of more than 2.0 seconds). As is the case with snoring, generally sleep partners are the ones who complain of tooth grinding sounds.

The causes of sleep bruxism are unknown. In the past, anxiety and life stress were suggested to be risk factors for bruxism. However, when one is asleep the area of the brain that deals with stress is not active.  Most sleep bruxism events tend to occur in clusters in relation to recurrent arousal (7 to 14 times per hour of sleep) with transient (3.0- to 10.0 seconds) reactivation of muscle tone, brain, and heart activities during sleep. Results based on the reports of sleep partners show at 8% of adults make tooth grinding sounds, a level that drops to 3% in older individuals, although this estimate is less precise because of the presence of dentures and habits of sleeping alone.

The physical consequences of sleep bruxism may include tooth destruction (tooth wear or restoration destruction), morning headache, jaw pain, and a limited ability to open the mouth due to muscle tension or meniscus displacement.

Dr. Nugent’s decision to request a sleep test may be based on frequent tooth grinding as reported by sleep partners, tooth damage, and orofacial pain or headache in relation to sleep. Patients with mild sleep bruxism will display more than two jaw muscle contractions per hour of sleep, and patients with moderate-to-severe sleep bruxism will have more than four such events per hour of sleep.


Also called catathrenia, groaning is rare condition (presented by 0.5% of patients in a sleep clinic) characterized by oral sounds that are dominant during REM sleep. Most frequently reported in young male subjects, catathrenia is associated with inarticulate speech sounds during a deep expiration. It may resemble sleep apnea.


Stridor is a high-pitched, wheezing sound caused by disrupted airflow. Stridor may also be called musical breathing or extrathoracic airway obstruction. Airflow is usually disrupted by a blockage in the larynx (voice box) or trachea (windpipe). Stridor affects children more often than adults.

Sleep-related laryngospasm

Sleep-related laryngospasm is characterized by abnormal laryngeal muscle activity. Patients report a sense of suffocation and anxiety, resulting in awakening in response to the interruption of airflow (5 to 45 seconds).

Sleep talking

Also called somniloquy, such sounds are usually associated with articulate speech with the production of words. Sleep talking occurs in 50% of children and only 5% of adults. The patient’s sleep partner is the key person when it comes to reporting this activity.


The throat clearing sound is a daytime tic that may persist during sleep.

Sleep suckling and smacking sounds

This rare condition’s cause is not known.

Sleep terrors

Sleep terrors are observed during non-REM deep sleep (stages 3 and 4). Sleep terrors are mainly observed in young patients but are also reported in 3% to 4% of adult patients. Sleep terrors are characterized by sudden awakening accompanied by a piercing scream or cry and incoherent vocalizations. Most patients are confused and rarely report dream content associated with the event. Body injuries can be reported as a result of the motor activity generated in the process.


Nightmares are much more frequent than sleep terrors and occur in REM sleep. They may be present if posttraumatic stress is part of the patient’s history.

Types of movement disorders that occur during sleep

Simple sleep-related movement disorders

  • Jaw and face: Bruxism, faciomandibular myoclonus
  • Legs: Restless legs syndrome/periodic limb movement in sleep (rare with sleep bruxism, occurring in less than 10% of cases, but may be concomitant with chronic pain); leg cramps (induce pain: increase with age; present in pregnant women); hypnagogic foot tremor/alternating leg muscle activation (can be triggered by antidepressant medications)
  • Childhood: Benign sleep twitches of jerking)
  • Miscellaneous: Excessive fragmentary twitches or jerking (small movements of fingers, toes, corners of mouths; more frequent in older men)

Complex sleep-related movement disorders

  • Parasomnias sleep disorders that involve abnormal movements, behaviors, emotions, perceptions, and dreams that occur while falling asleep, sleeping, between sleep stages, or during arousal from sleep. Disorders of partial arousal (parasomnia; sleepwalking, sleep terrors, confusional arousal)
  • Epilepsy during sleep (neurologic condition; must be excluded if the patient reports tooth tapping)

Movement disorders primarily observed during wakefulness and reduced during sleep

  • Parkinson disease
  • Huntington disease
  • Myoclonus
  • Ataxia
  • Dystonia
  • Essential tremor
  • Tourette syndrome
  • Hemiballismus

Movement-related Disorders

Movement disorders during sleep can be simple or complex. The ramifications of movement disorders can be minor or they can be associated with neurologic disorders that require a medical evaluation.

Abnormal swallowing and choking

It is normal to swallow saliva during sleep but at a lower frequency in comparison to when one is awake. However, in some patients, an undue accumulation of saliva can occur, predisposing a patient to choking. The condition may cause patients to become very anxious because of the inability to breath, the sensation of suffocation, and awakening in response to the high heart rate that may result from the condition.

Abnormal swallowing during sleep must be differentiated from the transient hypersalivation caused by the recent use of abnormal appliance (a mandibular advancement appliance).

Pain-Related Conditions

Gastroesophageal reflux disease

Also known as heartburn, GERD is characterized by the regurgitation of stomach contents into the esophagus and mouth. These events are common during sleep because the supine position expedite regurgitation. The patient may also produce wheezing-gasping sounds in addition to coughing and choking. During sleep, GERD can trigger painful sensations and awakening. GERD can mimic chest pain.


Fibromyalgia (also called widespread pain) is a clinical variety of chronic symptoms that includes pain, poor sleep, anxiety, mood alteration, and headache. It is estimated that more that 80% of patients with fibromyalgia may also suffer from poor sleep quality, unrefreshing sleep, TMDs or pain.


When a patient reports tension-type or temporal headaches on awakening, the dentist must screen for sleep bruxism or sleep-disordered breathing because morning headaches are frequently related complaints. Dentist should gather the patient’s and the sleep partners’ reports of snoring, cessation of breathing, and sleepiness by using the Epworth sleepiness scale questionnaire.

Migraine attacks can also be reported during the sleep period because about half of such attacks occur between 4 and 9am. Migraine attack mainly occur in relation to REM sleep, although they sometimes occur during deep sleep (stages 3 and 4).

Dentist, in collaboration with physicians, can apply their proficiency to recognize various sleep disorders and to manage snoring, sleep-disordered breathing, sleep bruxism, and sleep-related orofacial pain.

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