The essential feature of Primary Hypersomnia is excessive sleepiness for at least 1 month as evidenced either by prolonged sleep episodes or by daytime sleep episodes occurring almost daily (Criterion A). The excessive sleepiness must be sufficiently severe to cause clinically significant distress or impairment in social, occupational, or other important areas of functioning (Criterion B). The excessive sleepiness does not occur exclusively during the course of another Sleep Disorder (Criterion C) or mental disorder (Criterion D) and is not due to the direct physiological effects of a substance or a general medical condition (Criterion E).
In individuals with Primary Hypersomnia, the duration of the major sleep episode (for most individuals, nocturnal sleep) may range from 8 to 12 hours and is often followed by difficulty awakening in the morning. The actual quality of nocturnal sleep is normal. Excessive sleepiness during normal waking hours takes the form of intentional naps or inadvertent episodes of sleep. Objective measurements demonstrate increased physiological sleepiness. Daytime naps tend to be relatively long (often lasting an hour or more), are experienced as unrefreshing, and often do not lead to improved alertness. Individuals typically feel sleepiness developing over a period of time, rather than experiencing a sudden sleep “attack.” Unintentional sleep episodes typically occur in low-stimulation and low-activity situations (e.g., while attending lectures, reading, watching television, or driving long distances).
Hypersomnia can lead to significant distress and dysfunction in work and social relationships. Prolonged nocturnal sleep and difficulty awakening can result in difficulty in meeting morning obligations. Unintentional daytime sleep episodes can be embarrassing and even dangerous, if, for instance, the individual is driving or operating machinery when the episode occurs. The low level of alertness that occurs while an individual fights sleepiness can lead to poor efficiency, poor concentration, and poor memory during daytime activities. Sleepiness, often misattributed to boredom or laziness, can also disrupt social and family relationships.
Recurrent. This specifier is used if there are periods of excessive sleepiness that last at least 3 days occurring several times a year for at least 2 years.
Most individuals with Primary Hypersomnia have consistent and persistent symptoms. In contrast, the Recurrent form should be noted if symptoms occur periodically for several days to several weeks, with symptomatic periods recurring several times per year. Between periods of excessive sleepiness, sleep duration and daytime alertness are normal. In the recurrent form of Primary Hypersomnia known as Kleine-Levin syndrome, individuals may spend 18-20 hours asleep or in bed. The recurrent periods of sleepiness are associated with other characteristic clinical features indicating disinhibition. Indiscriminate hypersexuality including inappropriate sexual advances and overt masturbation can be seen in males (and less often in females). Compulsive overeating with acute weight gain may occur. Irritability, depersonalization, depression, confusion, and occasional hallucinations have been described in some individuals, and impulsive behaviors can also occur. Other recurrent forms of hypersomnia can be seen in the absence of these features. For instance, some females report regularly occurring periods of hypersomnia at specific times of their menstrual cycle.
Associated Features and Disorders
Associated descriptive features and mental disorders. In Primary Hypersomnia, sleep tends to be continuous but nonrestorative. Individuals with this disorder fall asleep quickly and have good sleep efficiency, but may have difficulty waking up in the morning, sometimes appearing confused, combative, or ataxic. This prolonged impairment of alertness at the sleep-wake transition is often referred to as “sleep drunkenness.”
Persistent daytime sleepiness can lead to automatic behavior (usually of a very routine, low-complexity type) that the individual carries out with little or no subsequent recall. For example, individuals may find themselves having driven several miles from where they thought they were, unaware of the “automatic” driving they did in the preceding minutes.
Although precise data are not available regarding comorbidity with mental disorders, many individuals with Primary Hypersomnia have symptoms of depression that may meet criteria for a Mood Disorder. This may be related to the psychosocial consequences of excessive sleepiness. Individuals with hypersomnia are also at risk for Substance-Related Disorders, particularly related to self-medication with stimulants.
Associated laboratory findings. In Primary Hypersomnia, nocturnal polysomnography demonstrates a normal to prolonged sleep duration, short sleep latency, normal to increased sleep continuity, and normal distributions of rapid eye movement (REM) and non-rapid eye movement (NREM) sleep. Some individuals with this disorder may have increased amounts of slow-wave sleep. Increased spindle density during stage 2 sleep may be present. Sleep-onset REM periods (the occurrence of REM sleep within 20 minutes of sleep onset), breathing-related sleep disturbances, and frequent limb movements disrupting sleep are not present. The Multiple Sleep Latency Test (MSLT) documents excessive physiological daytime sleepiness, typically indicated by mean sleep latency values of 5-10 minutes. REM sleep does not occur during the daytime sleep episodes. Nocturnal polysomnography and the MSLT do not reveal findings characteristic of other causes of hypersomnia.
In the Recurrent Kleine-Levin form of Primary Hypersomnia, routine EEG studies performed during the periods of hypersomnia show general slowing of the background rhythm and paroxysmal bursts of theta activity. Nocturnal polysomnography shows an increase in total sleep time and short REM sleep latency. MSLT studies confirm increased physiological sleepiness, with sleep latencies generally less than 10 minutes. Sleep-onset REM periods may be seen during symptomatic periods.
Associated physical examination findings and general medical conditions. Individuals with Primary Hypersomnia often appear sleepy and may even fall asleep in the clinician’s waiting area. A subset of individuals with Primary Hypersomnia have a family history of hypersomnia and also have symptoms of autonomic nervous system dysfunction, including recurrent vascular-type headaches, reactivity of the peripheral vascular system (Raynaud’s phenomenon), and fainting. Individuals with the Recurrent Kleine-Levin form may have nonspecific neurological examination findings including depressed deep tendon reflexes, dysarthria, and nystagmus.
Specific Age or Gender Features
Hyperactivity may be one of the presenting signs of daytime sleepiness in children. Voluntary napping increases with age, but this normal phenomenon is distinct from Primary Hypersomnia. Kleine-Levin syndrome affects males about three times more often than it affects females.
The true prevalence of Primary Hypersomnia in the general population is not known. Approximately 5%-10% of individuals who present to sleep disorders clinics with complaints of daytime sleepiness are diagnosed as having Primary Hypersomnia. The Recurrent form of Primary Hypersomnia known as Kleine-Levin syndrome is rare. Population surveys find a complaint of daytime sleepiness in 0.5%-5.0% of adults, without regard to specific causes or diagnoses. After other common causes are accounted for, the lifetime prevalence of clinically significant hypersomnia is at least 16%, and the incidence over approximately a 4-year interval is about 8%.
Primary Hypersomnia typically begins between ages 15 and 30 years, with a gradual progression over weeks to months. For most individuals, the course is then chronic and stable, unless treatment is initiated. The development of other sleep disorders (e.g., Breathing-Related Sleep Disorder) may worsen the degree of sleepiness. Kleine-Levin syndrome also begins during adolescence and may continue its periodic course for decades, although it often resolves during middle age.
The subgroup of individuals with autonomic dysfunction are more likely than other individuals with Primary Hypersomnia to have family members with Primary Hypersomnia. Kleine-Levin syndrome does not demonstrate familial aggregation.
“Normal” sleep duration varies considerably in the general population. “Long sleepers” (i.e., individuals who require a greater than average amount of sleep) do not have excessive daytime sleepiness, sleep drunkenness, or automatic behavior when they obtain their required amount of nocturnal sleep. If social or occupational demands lead to shorter nocturnal sleep, daytime symptoms may appear. In Primary Hypersomnia, by contrast, symptoms of excessive sleepiness occur regardless of nocturnal sleep duration.
An inadequate amount of nocturnal sleep can produce symptoms of daytime sleepiness very similar to those of Primary Hypersomnia. An average sleep duration of fewer than 7 hours per night strongly suggests inadequate nocturnal sleep, and an average of more than 9 hours of sleep per 24-hour period suggests Primary Hypersomnia. Individuals with inadequate nocturnal sleep typically “catch up” with longer sleep durations on days when they are free from social or occupational demands or on vacations. Unlike Primary Hypersomnia, insufficient nocturnal sleep is unlikely to persist unabated for decades. A diagnosis of Primary Hypersomnia should not be made if there is a question regarding the adequacy of nocturnal sleep duration. A diagnostic and therapeutic trial of sleep extension for 10-14 days can often clarify the diagnosis.
Daytime sleepiness, which is a characteristic feature of Primary Hypersomnia, can also occur in Primary Insomnia, but the sleepiness or fatigue is less severe in individuals with Primary Insomnia. When daytime sleepiness is judged to be due to insomnia, an additional diagnosis of Primary Hypersomnia is not given.
Primary Hypersomnia and Narcolepsy are similar with respect to the degree of daytime sleepiness, age at onset, and stable course over time but can be distinguished based on distinctive clinical and laboratory features. Individuals with Primary Hypersomnia typically have longer and less disrupted nocturnal sleep, greater difficulty awakening, more persistent daytime sleepiness (as opposed to more discrete “sleep attacks” in Narcolepsy), longer and less refreshing daytime sleep episodes, and little or no dreaming during daytime naps. By contrast, individuals with Narcolepsy have cataplexy and recurrent intrusions of elements of REM sleep into the transition between sleep and wakefulness (e.g., sleep-related hallucinations and sleep paralysis). The MSLT typically demonstrates shorter sleep latencies (i.e., greater physiological sleepiness) as well as the presence of multiple sleep-onset REM periods in individuals with Narcolepsy.
Individuals with Primary Hypersomnia and Breathing-Related Sleep Disorder may have similar patterns of excessive sleepiness. Breathing-Related Sleep Disorder is suggested by a history of loud snoring, pauses in breathing during sleep, brain injury, or cardiovascular disease and by the presence of obesity, oropharyngeal anatomical abnormalities, hypertension, or heart failure on physical examination. Polysomnographic studies can confirm the presence of apneic events in Breathing-Related Sleep Disorder (and their absence in Primary Hypersomnia).
Circadian Rhythm Sleep Disorder is often characterized by daytime sleepiness. A history of an abnormal sleep-wake schedule (with shifted or irregular hours) is present in individuals with Circadian Rhythm Sleep Disorder. Parasomnias rarely produce the prolonged, undisturbed nocturnal sleep or daytime sleepiness characteristic of Primary Hypersomnia.
Primary Hypersomnia must be distinguished from mental disorders that include hypersomnia as an essential or associated feature. In particular, complaints of daytime sleepiness may occur in a Major Depressive Episode, With Atypical Features, and in the depressed phase of Bipolar Disorder. The diagnosis of Primary Hypersomnia is not given if hypersomnia occurs exclusively during the course of another mental disorder. A thorough investigation for the presence of other mental disorders is essential before considering the diagnosis of Primary Hypersomnia. A diagnosis of Primary Hypersomnia can be made in the presence of another current or past mental disorder if the mental disorder is judged to not account for the hypersomnia or if the hypersomnia and the mental disorder have an independent course (e.g., in an individual with chronic hypersomnia who later develops a Major Depressive Disorder). In contrast, when hypersomnia occurs as a manifestation of, and exclusively during the course of, another mental disorder, the diagnosis of Hypersomnia Related to Another Mental Disorder may be more appropriate. This diagnosis should only be considered when the hypersomnia is the predominant complaint and is sufficiently severe to warrant independent clinical attention; otherwise, no separate diagnosis is necessary. In general, laboratory testing of daytime sleepiness in individuals with Hypersomnia Related to a Mental Disorder often shows normal or only mild levels of physiological sleepiness compared with individuals with Primary Hypersomnia.
Primary Hypersomnia must be distinguished from Sleep Disorder Due to a General Medical Condition, Hypersomnia Type. The diagnosis is Sleep Disorder Due to a General Medical Condition when the hypersomnia is judged to be a direct physiological consequence of a specific general medical condition (e.g., morbid obesity, brain tumor). This determination is based on history, laboratory findings, or physical examination. Substance-Induced Sleep Disorder, Hypersomnia Type, is distinguished from Primary Hypersomnia by the fact that a substance (i.e., a drug of abuse, a medication, or exposure to a toxin) is judged to be etiologically related to the hypersomnia. For example, hypersomnia occurring only in the context of withdrawal from cocaine would be diagnosed as Cocaine-Induced Sleep Disorder, Hypersomnia Type, With Onset During Withdrawal.
Relationship to the International Classification of Sleep Disorders
Primary Hypersomnia is analogous to the diagnosis of Idiopathic Hypersomnia in the International Classification of Sleep Disorders (ICSD). In addition, the ICSD includes a separate category for Recurrent Hypersomnia, which is analogous to the Recurrent form of Primary Hypersomnia.
Diagnostic criteria for 307.44 Primary Hypersomnia
A. The predominant complaint is excessive sleepiness for at least 1 month (or less if recurrent) as evidenced by either prolonged sleep episodes or daytime sleep episodes that occur almost daily.
B. The excessive sleepiness causes clinically significant distress or impairment in social, occupational, or other important areas of functioning.
C. The excessive sleepiness is not better accounted for by insomnia and does not occur exclusively during the course of another Sleep Disorder (e.g., Narcolepsy, Breathing-Related Sleep Disorder, Circadian Rhythm Sleep Disorder, or a Parasomnia) and cannot be accounted for by an inadequate amount of sleep.
D. The disturbance does not occur exclusively during the course of another mental disorder.
E. The disturbance is not due to the direct physiological effects of a substance (e.g., a drug of abuse, a medication) or a general medical condition.
Recurrent: if there are periods of excessive sleepiness that last at least 3 days occurring several times a year for at least 2 years
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