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How it’s defined, its causes, and the steps that can help resolve it

Rob Newsom

Written by

Rob Newsom, Staff Writer

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Excessive sleepiness, also called hypersomnolence, is a common experience for one-third of Americans that are chronically sleep-deprived. According to a National Sleep Foundation Sleep in America poll, 43% of people report that daytime sleepiness interferes with their activities at least a few days a month. One in five report experiencing daytime sleepiness at least a few days a week.

Hypersomnolence is not a disorder in itself, it’s a symptom of other conditions. Most cases of excessive sleepiness are related to insufficient or interrupted sleep. Poor sleep may result from a variety of conditions, including sleep disorders like insomnia, obstructive sleep apnea, and sleep-related movement disorders.

For some people though, extreme tiredness isn’t the result of other conditions and can’t be relieved after a full night’s rest. When hypersomnolence is not caused by disrupted sleep or another sleep disorder, it may be classified as a central disorder of hypersomnia.

What is Hypersomnia?

Hypersomnia is a medical term used to describe a variety of conditions in which a person feels excessively tired or sleeps longer than usual. Some researchers classify hypersomnia as either primary or secondary. Primary hypersomnia is a neurological condition that occurs on its own and has no known underlying cause. Secondary hypersomnia occurs as the result of an underlying medical condition.

Secondary Hypersomnias

Hypersomnia, or excessive sleepiness, is often secondary to, or a symptom of, other medical conditions. Hypersomnia can be classified as secondary when it is due to medical conditions, medications, substances, psychiatric disorders, or insufficient sleep syndrome.

  • Hypersomnia due to a medical condition: Medical conditions that may cause hypersomnia include Parkinson’s disease, epilepsy, hypothyroidism, multiple sclerosis, and even obesity. Hypersomnia can also develop as a result of tumors, traumatic brain injuries, and diseases of the nervous system.
  • Hypersomnia due to a medication or substance: Certain sedating medications, alcohol, and drug use can cause hypersomnia. Hypersomnia can also be a symptom of withdrawal from stimulant drugs and some medications.
  • Insufficient sleep syndrome: Perhaps the most straightforward cause of hypersomnia, insufficient sleep syndrome occurs when a person persistently fails to get sufficient sleep. Poor sleep hygiene or night shift work may cause a person to develop the inability to obtain the required amount of sleep.
  • Hypersomnia associated with a psychiatric disorder: Many mood disorders may cause hypersomnia, including depression, bipolar disorder, and seasonal affective disorder.

Primary Hypersomnias

Primary hypersomnia describes hypersomnia that occurs on its own and is not secondary to another condition. Central disorders of hypersomnia that can be classified as primary include narcolepsy type 1 and type 2, Kleine-Levin syndrome, and idiopathic hypersomnia.

  • Narcolepsy type 1: Narcolepsy type 1, also called narcolepsy with cataplexy, is a chronic neurological disorder caused by an insufficient amount of a neurotransmitter called orexin. Although hypersomnolence is one symptom of narcolepsy type 1, other symptoms include cataplexy (sudden muscle weakness), sleep paralysis, and hallucinations.
  • Narcolepsy type 2: Narcolepsy type 2 includes many of the same symptoms of type 1, but doesn’t include cataplexy and isn’t caused by a loss of orexin.
  • Kleine-Levin syndrome: Kleine-Levin syndrome is characterized by recurring episodes of extreme hypersomnolence that occur alongside mental, behavioral, and even psychiatric disturbances. This condition primarily affects young males and episodes often decrease over a period of 8 to 12 years.
  • Idiopathic hypersomnia: If a patient has excessive sleepiness, without cataplexy, that isn’t refreshed by naps or sleep, they may be diagnosed with idiopathic hypersomnia.



Idiopathic Hypersomnia

Idiopathic hypersomnia (IH) is a sleep disorder in which a person feels excessive tiredness, even after a full and uninterrupted night of sleep. People with this condition may sleep longer than normal, sometimes 11 or more hours a night, yet still feel tired during the day.

Other potential symptoms of IH include non-restorative naps and feelings of grogginess after waking, called sleep inertia. Sleep inertia, sometimes also referred to as sleep drunkenness, can be severe in people suffering from IH. The transition from sleep to wakefulness can take up to several hours, leaving a person feeling mentally foggy and having difficulty engaging in even the most basic tasks—like getting out of bed.

In people with IH, hypersomnolence can happen at any time during the day or night. Excessive tiredness can cause significant challenges at work, school, and in personal relationships. Along with sleepiness, patients with IH may experience mood changes, slowed thinking and reaction times, and memory challenges.

Causes of Idiopathic Hypersomnia

While the exact causes of IH are not known, researchers have investigated a number of potential factors that may contribute to the development of idiopathic hypersomnia. Several studies have looked at the potential roles of neurotransmitters, including orexins, dopamine, serotonin, histamines, and gamma-aminobutyric acid (GABA). Research suggests that there may also be a genetic component to IH since a family history of the condition is present in 26% to 39% of IH patients.

Although one diagnostic criteria for IH is that its symptoms aren’t caused by a circadian rhythm disorder, some research suggests that there may be a connection between IH and the body’s internal clock. Studies have found that the regulation of certain genes involved in circadian rhythm may be different in people with IH.

Diagnosing Idiopathic Hypersomnia

Idiopathic hypersomnia appears to be a rare condition, but its exact prevalence is difficult to determine. Symptoms often appear in a person’s teens or early twenties, although they can begin at any age.

DIagnosing IH often begins by determining if a patient’s hypersomnia is secondary to another health condition. If an underlying cause of hypersomnia can’t be found, a diagnosis of IH may be made based on a person’s symptoms and the results of sleep tests. According to the International Classification of Sleep Disorders, several important criteria must be met for a person to be diagnosed with idiopathic hypersomnia:

  • Daily periods of excessive sleepiness, or daytime lapses into sleep, for at least 3 months
  • No evidence of cataplexy or sudden muscle weakness
  • Results from a multiple sleep latency test (MSLT) show a sleep latency (time to fall asleep) of less than 8 minutes or a total sleep time of 11 or more hours
  • Characteristic measurements of how long it takes to reach the REM sleep stage
  • Insufficient sleep syndrome is ruled out, as is hypersomnia due to medical conditions, medications, substances, or psychiatric disorders

Idiopathic Hypersomnia and Narcolepsy Type 2

Even with specific criteria for classifying different central disorders of hypersomnolence, there is controversy surrounding how to distinguish idiopathic hypersomnia from narcolepsy type 2. Long sleep times, which are often—but not always—seen in patients with IH, are also seen in 18% of people with narcolepsy. Limitations of the MSLT in measuring sleep latency and the time to reach REM sleep have resulted in many researchers noting that current testing sometimes cannot reliably tell these two conditions apart.

Treating Idiopathic Hypersomnia

Although there are no FDA-approved treatments for idiopathic hypersomnia in the United States, research suggests that the majority of patients respond well to treatment. Several treatments used to treat narcolepsy may be used off-label with IH patients to help reduce sleepiness, increase wakefulness, and improve daytime functioning.

Although several medications may help reduce IH symptoms, they can also come with challenging side effects and become less effective over time. A doctor is in the best position to help patients weigh the risks and benefits of off-label treatments for IH, so finding a doctor or sleep specialist is an important first step.

Sometimes IH patients find themselves improving without treatment. Research shows that up to 20% of patients may have a spontaneous remission of IH, with symptoms unexpectedly improving without medication.

Tips for Coping With Idiopathic Hypersomnia

In addition to medical treatments for idiopathic hypersomnia, the following lifestyle changes may help reduce symptoms and avoid injury caused by excessive tiredness:

  • Avoid anything that makes the condition worse: Alcohol, caffeine, and some medications may make the symptoms of IH more severe, so talk with a doctor or specialist about what to avoid in terms of diet and medication.
  • Be careful about driving: Driving a car or operating equipment can be dangerous for people with IH. Work with doctors, employers, and loved ones to make appropriate lifestyle and workplace adaptations.
  • Avoiding the night shift: Any activity that delays a person’s bedtime should be avoided in patients with IH. Always going to bed at the same time, even on weekends, may minimize symptoms.

Many people with IH find it helpful to talk to a psychologist, counselor, or support group to learn to cope with the significant challenges caused by IH symptoms. Educating employers, family, and friends about IH may also be helpful, so accommodations can be made at school, work, and in relationships.

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About Our Editorial Team

Rob Newsom

Staff Writer

Rob writes about the intersection of sleep and mental health and previously worked at the National Cancer Institute.


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