These symptoms increase when the person drinks alcohol, takes a depressant drug, or changes sleep patterns. There may also be a reduction in intellectual capacity, personality changes, sudden bursts of anger and hostility, and impairments in social and work life (Epstein et al., 2009).

The pathophysiology of narcolepsy results in a disturbance of control of both REM and NREM sleep-onset and -offset. There is resulting disruption of nighttime sleep and the impingement of sleep into daytime wakefulness (Nishino, 2007). Narcolepsy is considered a disorder of REM sleep mechanisms that causes hypnagogic hallucinations and sleep paralysis (Nishino, 2007). Research has also shown a correlation of narcolepsy with hypocretin ligand deficiency and dysregulation in the hypocretin-signaling pathway (Nishino, 2007). There is no strong evidence of inflammatory processes or immune abnormalities associated with narcolepsy, and studies have found neither classical autoantibodies nor an increase in oligoclonal cerebrospinal fluid (CSF) bands in narcoleptics (Nishino, 2007).

EPIDEMIOLOGY

Studies show a 1-year prevalence rate of insomnia complaints of 30% to 40% in the general population and up to 66% in the primary care and psychiatric settings (Ohayon, 2002). The prevalence of primary insomnia as a specific disorder is in the range of 5% to 10% of the general population (Ohayon, 2002). Approximately 5% to 10% of individuals who consult in sleep disorders clinics with complaints of daytime sleepiness are diagnosed as having hypersomnolence disorder (APA, 2013). It is estimated that about 1% of the European and U.S. general population has episodes of sleep inertia (Ohayon, Priest, Zulley, Smirne, & Paiva, 2002; Ohayon, Riemann, Morin, & Reynolds, 2012). Hypersomnolence occurs with relatively equal frequency in males and females (Ohayon et al., 2012). The incidence of narcolepsy is estimated at 0.02% to 0.18%, with a prevalence of more than 1 per 2,000, and a genetic linkage (Nishino, 2007). Narcolepsy occurs in 10% of first-degree relatives and excessive daytime sleepiness (EDS) in up to 30% (Nishino, 2007).

OSA predominantly affects middle-aged, overweight men; however, it can occur at all ages and in both sexes (Azagra-Calero, Espinar-Escalona, Barrera-Mora, Llamas-Carreras, & Solano-Reina, 2012). The prevalence is approximately 4% in men and 2% in women, with higher rates in African Americans, older people, obese people, and those with hypertension, hypothyroidism, and upper airway anatomic abnormalities (Lam, Sharma, & Lam, 2010).

RLS occurs in 5% to 10% of the population, with a strong family history. The rate of PLMD increases in patients older than age 60 years; it occurs rarely in patients younger than 30 years and is found in nearly half of patients older than 65 years (Silber, 2013).

There is an increase in sleep disturbances in the elderly, with a greater number of awakenings, possibly as a result of the increased incidence of sleep-related breathing disorders (mild apnea) and PLMD. The elderly also sleep less efficiently and have more circadian rhythm changes (Crowley, 2011).

DIAGNOSTIC CRITERIA

Many patients with insomnia can be successfully managed by a primary care provider. An in-depth interview to obtain a full description of the problem is the most important diagnostic procedure. A sleep laboratory study (PSG) may also be indicated. Changes in sleep habits and patterns should alert the primary care provider to the possibility of a sleep disorder; however, not all disturbances in sleep are symptomatic of a primary sleep disorder. It is important to inquire about sleep as part of the routine assessments, because some patients will not describe problems otherwise. An accurate diagnosis can be difficult, because many different sleep disorders share signs and symptoms (APA, 2013).

There is frequently a close connection and interaction between the quality of sleep and health problems (Crowley, 2011). The primary care provider should listen carefully for symptoms of depression, bipolar disease, anxiety disorder, panic disorder, substance abuse, or psychosis. Disordered sleep is also found in dementia, parkinsonism, epilepsy, nocturnal cardiac ischemia, sleep-related gastroesophageal reflux, peptic ulcer disease, sleep-related asthma, and fibromyalgia.

The DSM-5 classifies sleep–wake disorders into ten main categories:

The method taken to change the classification of sleep–wake disorders in the DSM-5 can be understood within the context of “lumping versus splitting” (APA, 2013). The DSM-IV exemplified an effort to simplify sleep–wake disorders classification and thus combined diagnoses under broader, less-differentiated labels (APA, 2013). At the other pole, the ICSD-2 elaborates numerous diagnostic subtypes. The DSM-IV was prepared for use by mental health and general medical clinicians who are not experts in sleep medicine. ICSD-2 reflected the science and opinions of the sleep specialist community and was prepared for intended use by specialists.

Detailed criteria are available in the DSM-5. The essential feature of insomnia disorder is dissatisfaction with sleep quantity or quality with complaints of difficulty initiating or maintaining sleep (APA, 2013). The sleep complaints must be accompanied by clinically significant distress or impairment in social, occupational, or other important areas of functioning. The sleep disturbance may occur during the course of another mental disorder or medical condition, or it may occur independently.

Patients may also have complaints of irritability, difficulty concentrating, or problems with inattention. Not all individuals with nighttime sleep disturbances are distressed or have functional impairment (APA, 2013). For example, sleep continuity is often interrupted in healthy older adults who nevertheless identify themselves as good sleepers. A diagnosis of insomnia disorder should be reserved for those individuals with significant daytime distress or impairment related to their nighttime sleep difficulties (APA, 2013).

Hypersomnolence Disorder

Refer to the DSM-5 for a complete listing of the diagnostic criteria for hypersomnolence disorder. Hypersomnolence is considered a broad diagnostic term and includes symptoms of excessive quantity of sleep (e.g., extended nocturnal sleep or involuntary daytime sleep), deteriorated quality of wakefulness (i.e., sleep propensity during wakefulness as shown by difficulty awakening or inability to remain awake when required), and sleep inertia (i.e., a period of impaired performance and reduced vigilance following awakening from the regular sleep episode or from a nap; APA, 2013). Individuals with this disorder fall asleep quickly and have a good sleep efficiency (>90%); however they may have trouble waking up in the morning, appearing confused, combative, or ataxic. This prolonged impairment of alertness at the sleep–wake transition is often referred to as sleep inertia (i.e., sleep drunkenness; APA, 2013). It can also occur upon awakening from a daytime nap. During that period, the individual appears awake, but there is a decline in motor dexterity, behavior may be very inappropriate, and memory deficits, disorientation in time and space, and feelings of grogginess may occur (APA, 2013). This period may last some minutes to hours.

Narcolepsy

The diagnostic criteria for narcolepsy are found in the DSM-5. Narcolepsy is characterized by EDS and is often associated with cataplexy. The cataplexic attacks may be either a barely observable brief weakness of a muscle group resulting in the jaw dropping, losing of one’s grip, or a total collapse after sudden paralysis. Narcolepsy usually develops in the second decade of life and progresses slowly but steadily. The sleep attacks are often irresistible and may last from minutes to an hour, after which the person feels refreshed. The attacks may occur many times daily during periods of either activity or inactivity. The patient may collapse suddenly without warning. The patient may experience a sleep paralysis on falling asleep or awakening; in this situation, the patient is unable to move a muscle, or breathing feels paralyzed. The patient often experiences panic when this first begins to occur (Bassetti, Billiard, & Mignot, 2007).

Narcolepsy with cataplexy nearly always results from the loss of hypothalamic hypocretin(orexin)–producing cells, causing hypocretin deficiency (<110 pg/mL in most laboratories; APA, 2013). Cell loss is likely autoimmune, and research has shown that approximately 99% of affected individuals carry HLA-DQB1*06:02 (Bourgin, Zeitzer, & Mignot, 2008). Thus, checking for the presence of DQB1*06:02 prior to a lumbar puncture for evaluation of CSF hypocretin-1 immunoreactivity may be useful. CSF hypocretin-1 measurement represents the gold standard, excluding associated severe conditions (neurological, inflammatory, infectious, and trauma) that can interfere with the assay (Bourgin et al., 2008).

A nocturnal PSG sleep study followed by a multiple sleep latency test (MSLT) can also be used to confirm the diagnosis. However, these tests must be performed after the individual has discontinued all psychotropic medications, following 2 weeks of adequate sleep time. Short REM latency (sleep-onset REM period, REM latency ≤15 minutes) during PSG is sufficient to confirm the diagnosis (APA, 2013). Alternatively, the MSLT result must be positive, showing a mean sleep latency of ≤8 minutes and two or more sleep-onset REM periods in four to five naps (Bassetti et al., 2007; Dauvilliers, Arnulf, & Mignot, 2007).

Obstructive Sleep Apnea

OSA is a form of sleep-related breathing disorder characterized by repetitive intervals of upper airway obstruction. These episodes last longer than 10 seconds in adults or two missed breaths in children and occur more than 30 times during both REM and NREM sleep in a 7-hour sleep period. Each apnea of hypopnea is typically associated with drops in oxygen saturation of 3% or greater and/or an electro-encephalographic arousal (APA, 2013). However, patients may have more episodes than this, and the obstructive time periods may last up to 2 minutes (Epstein et al., 2009). An OSA can be thought of as a continuum from normal sleep to severe, all-night OSA.

OSA hypopnea in adults is diagnosed on the basis of PSG findings and symptoms (APA, 2013). The diagnosis is based on symptoms which include: nocturnal breathing disturbances, or daytime sleepiness, fatigue, or unrefreshing sleep despite sufficient opportunities to sleep that are not better explained by another mental disorder and not attributable to another medical condition, along with evidence by PSG of five or more obstructive apneas or hypopneas per hour of sleep (APA, 2013). Diagnosis can be made in the absence of these symptoms if there is evidence by PSG of 15 or more obstructive apneas and/or hypopneas per hour of sleep (APA, 2013).

Periodic Limb Movement Disorder

PLMD, also known as nocturnal myoclonus, results in periodic, repetitive movements of the limbs during sleep. Patients complain of nonrefreshing sleep and are unaware of the movements, although they may have brief arousals or even full awakenings. Information from a bed partner can be very helpful in making this diagnosis. Both the quality and quantity of sleep are affected. PSG readings, including an electromyogram (EMG) and an EEG, are essential for diagnosis. An EMG shows either a series of bursts or single sustained contractions in the anterior tibialis muscles bilaterally, the biceps, or the triceps. The EEG shows a K complex followed by a brief alpha rhythm. The movements are stereotypical and rhythmic and include rapid flexion or jerking of the legs and feet (Silber, 2013).

Restless Legs Syndrome

RLS is related to PLMD. Almost all patients with RLS also have PLMD, but the reverse is not true. The diagnosis of RLS can be made from the history and description of symptoms. Symptoms of RLS include pricking, tingling, creeping, and crawling sensations deep in the (usually lower) legs that escalate to an irresistible urge to move the legs. The symptoms occur at rest, usually when lying down, and worsen toward evening, thus interfering with both sleep onset and continuity of sleep. RLS is exacerbated by: