Hypersomnia is best understood as the opposite of insomnia. Whereas an insomniac struggles to achieve sleep at night, a hypersomniac struggles to stay awake during the day. It's estimated that maybe as many as five percent of the population suffers from some form of hypersomnia that is not explained by other medical conditions or lifestyle choices. Hypersomnia usually refers to a symptom (the same can be said for insomnia). However, primary forms do exist along the spectrum of sleep disorders.
The chronic sleepiness that characterizes hypersomnia (also referred to as hypersomnolence) is most frequently referred to as excessive daytime sleepiness (EDS) by sleep health professionals. It happens even when the person has had adequate sleep during the evening and is not remedied by getting more sleep.
People with hypersomnia as a primary complaint may actually be suffering from undiagnosed sleep disorders like Restless Leg Syndrome (RLS) or Obstructive Sleep Apnea. If this is the case, their problems with EDS tend to disappear once they treat their other sleep disorders. The best way to know if other sleep disorders are causing symptomatic hypersomnia is to undergo an overnight sleep test (an attended nocturnal polysomnogram) as well as a daytime "nap" test known as the MSLT (Multiple Sleep Latency Test).
The sleep disorders discussed below belong in the category of Central Disorders of Hypersomnolence, according to the ICSD-3.
Narcolepsy is a neurological sleep disorder which results in involuntary "attacks" of sleep (or sleep-like behavior) during the day, usually brought on by emotional triggers. Narcoleptics struggle with EDS as well as sleep paralysis at night, hallucinations before sleep onset or at the end of sleep, and sometimes (though not always) a condition called cataplexy, in which the narcoleptic's body literally collapses on the spot due to emotional triggers. These collapses give the appearance that the person is asleep, but in fact, they are often awake.
They may also suffer from disturbed sleep, vivid dreams, automatic behavior (in which they experience microsleep-like behavior during activity and yet continue the activity) and problems with focus and memory. It's caused by low levels of a wakefulness chemical in the brain called hypocretin (aka orexin) or disruptions in the central nervous system which prevent its proper release. How the levels become low is not well understood, except that it might be due to heredity, infection, traumatic brain injury, autoimmune problems, low histamine levels or environmental triggers.
Narcolepsy is diagnosed through a specific batch of sleep tests: the overnight sleep study (NPSG) and the Multiple Sleep Latency Test (MSLT), which measures how quickly it takes the patient to fall asleep during the day.
Kleine-Levin Syndrome (KLS) is more popularly known as Sleeping Beauty Syndrome, in which the sufferer may encounter episodic hypersomnia for days or weeks at a time. Onset of this rare (one in a million occurrence) sleep disorder is generally blamed on viral triggers; several viruses have been shown to cause KLS. It generally affects adolescent males but can happen to anyone. Other symptoms of KLS include excessive appetite and unusual cravings for food, increased sexual urges, changes in mood, cognitive dysfunction, and an overwhelming sense of malaise.
KLS is a sleep disorder that is diagnosed based on symptoms and history and only after eliminating any number of other medical conditions that might be at the root of both the hypersomnolence and unusual behavior.
Idiopathic Hypersomnia refers to a diagnosis that occurs when chronic hypersomnolence cannot be explained by any other preexisting medical condition or sleep disorder or by lifestyle or behavior.
In some cases, IH is "resolved" when the patient diagnosed with it discovers they have another illness that is causing the hypersomnolence. Treatment of that illness often improves their problems with sleepiness. IH can no longer be "idiopathic" if a root cause can be identified.
However, for some, IH is a differential diagnosis that can identify no apparent root cause, and that is what makes it so mysterious for patients and physicians to understand and to treat.
All occurrences of hypersomnia can be very difficult to live with, as the need to sleep during the day interrupts the personal, social and professional lives of its sufferers in such a way as to make normal living (including physical activities and relationships) difficult to manage.
Treatments for these presentations of hypersomnolence depend upon diagnosis.
- Narcoleptics have a few medications to help them balance hypocretin levels and stay awake during the day.
- People with KLS have few options because of the mysterious nature of their disorder.
- Idiopathic Hypersomnia is a diagnosis of exclusion; it can, in fact, be "undiagnosed" once other health conditions are discovered which explain the source of the hypersomnolence. Treating that newly diagnosed medical condition may or may not improve the hypersomnia, but generally speaking, doctors are going to attribute a patient's problems with irresistible sleepiness to a known medical condition, as it is mostly likely to be its root cause.