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Disease Profile

Idiopathic hypersomnia

Prevalence estimates on Rare Medical Network websites are calculated based on data available from numerous sources, including US and European government statistics, the NIH, Orphanet, and published epidemiologic studies. Rare disease population data is recognized to be highly variable, and based on a wide variety of source data and methodologies, so the prevalence data on this site should be assumed to be estimated and cannot be considered to be absolutely correct.


US Estimated

Europe Estimated

Age of onset

All ages





Autosomal dominant A pathogenic variant in only one gene copy in each cell is sufficient to cause an autosomal dominant disease.


Autosomal recessive Pathogenic variants in both copies of each gene of the chromosome are needed to cause an autosomal recessive disease and observe the mutant phenotype.


dominant X-linked dominant inheritance, sometimes referred to as X-linked dominance, is a mode of genetic inheritance by which a dominant gene is carried on the X chromosome.


recessive Pathogenic variants in both copies of a gene on the X chromosome cause an X-linked recessive disorder.


Mitochondrial or multigenic Mitochondrial genetic disorders can be caused by changes (mutations) in either the mitochondrial DNA or nuclear DNA that lead to dysfunction of the mitochondria and inadequate production of energy.


Multigenic or multifactor Inheritance involving many factors, of which at least one is genetic but none is of overwhelming importance, as in the causation of a disease by multiple genetic and environmental factors.


Not applicable


Other names (AKA)

Idiopathic hypersomnolence; Primary hypersomnia


Idiopathic hypersomnia (IH) is a neurological sleep disorder that can affect many aspects of a person's life. Symptoms often begin between adolescence and young adulthood and develop over weeks to months. People with IH have a hard time staying awake and alert during the day (chronic excessive daytime sleepiness, or EDS). They may fall asleep unintentionally or at inappropriate times, interfering with daily functioning. They may also have difficulty waking up from nighttime sleep or daytime naps. Sleeping longer at night does not appear to improve daytime sleepiness.[1] IH is a chronic disorder. Symptoms may remain generally stable over time, or severity may fluctuate over time.[1][2]

The cause of IH is not known. Some people with IH have other family members with a sleep disorder such as IH or narcolepsy.[1] Currently there is no treatment approved by the FDA specifically for IH, but some people may be helped by medications used to treat other disorders ("off-label") such as narcolepsy.[1][3] Unlike in narcolepsy, in which scheduled naps may help, daytime naps in people with IH are often long yet unrefreshing.[1][4] People with IH may experience improvement with medication; however, medications do not work well for all people or may stop working over time.[1][3]


Common symptoms of idiopathic hypersominia (IH) include:[5][6][2]

  • Chronic excessive daytime sleepiness (EDS): sleepiness during the day that makes it difficult to perform normal daily activities, including both workand social-related activities.
  • Sleeping 9 hours or more over 24-hour periods, yet not feeling refreshed upon waking from nighttime sleep or naps.
  • Non-refreshing daytime napping.
  • Sleep drunkeness after nighttime sleep and naps: difficulty waking up and feeling an uncontrollable desire to go back to sleep.
  • "Brain fog" while awake: experiencing problems with memory, attention and concentration.
  • Headaches.

Other symptoms reported by people with IH include:[5][6][2]

This table lists symptoms that people with this disease may have. For most diseases, symptoms will vary from person to person. People with the same disease may not have all the symptoms listed. This information comes from a database called the Human Phenotype Ontology (HPO) . The HPO collects information on symptoms that have been described in medical resources. The HPO is updated regularly. Use the HPO ID to access more in-depth information about a symptom.

Medical Terms Other Names
Learn More:
80%-99% of people have these symptoms
Excessive daytime somnolence
Excessive daytime sleepiness
More than typical sleepiness during day

[ more ]

Excessive sleepiness


Treatments for hypersomnia are generally aimed at excessive daytime sleepiness (EDS), rather than at sleep duration or sleep drunkenness (confusion upon waking up). Although there are multiple treatments approved by the Food and Drug Administration (FDA) for narcolepsy, there are no FDA-approved treatments idiopathic hypersomnia (IH). Therefore, treatment generally involves off-label use of medications approved for narcolepsy. Unfortunately, the use of these medications is inadequate to improve symptoms in many people with IH. These medication options may include:[7]

There are also several emerging therapies for cases that do not respond to the above types of medications. These include sodium oxybate, clarithromycin, and flumazenil.[7]

Non-medical approaches such as behavior modification are not generally effective for people with IH. Unlike in narcolepsy, where scheduled naps can help, daytime naps in people with IH are typically long and nonrestorative.[1]

People with IH should avoid activities that may be dangerous, and should avoid driving or operating dangerous machinery unless sleepiness is well controlled by medication.[1]

Following up with physicians at least annually (preferably more frequently) is recommended to assess for side effects of medication, sleep or mood disturbances, adequate control of symptoms, and any work-related or social issues.[1]


Support and advocacy groups can help you connect with other patients and families, and they can provide valuable services. Many develop patient-centered information and are the driving force behind research for better treatments and possible cures. They can direct you to research, resources, and services. Many organizations also have experts who serve as medical advisors or provide lists of doctors/clinics. Visit the group’s website or contact them to learn about the services they offer. Inclusion on this list is not an endorsement by GARD.

Organizations Supporting this Disease

    Learn more

    These resources provide more information about this condition or associated symptoms. The in-depth resources contain medical and scientific language that may be hard to understand. You may want to review these resources with a medical professional.

    Where to Start

    • MedlinePlus was designed by the National Library of Medicine to help you research your health questions, and it provides more information about this topic.
    • The Merck Manuals Online Medical Library provides information on this condition for patients and caregivers.

      In-Depth Information

      • Medscape Reference provides information on this topic. You may need to register to view the medical textbook, but registration is free.
      • MeSH® (Medical Subject Headings) is a terminology tool used by the National Library of Medicine. Click on the link to view information on this topic.
      • The Monarch Initiative brings together data about this condition from humans and other species to help physicians and biomedical researchers. Monarch’s tools are designed to make it easier to compare the signs and symptoms (phenotypes) of different diseases and discover common features. This initiative is a collaboration between several academic institutions across the world and is funded by the National Institutes of Health. Visit the website to explore the biology of this condition.
      • Orphanet is a European reference portal for information on rare diseases and orphan drugs. Access to this database is free of charge.
      • PubMed is a searchable database of medical literature and lists journal articles that discuss Idiopathic hypersomnia. Click on the link to view a sample search on this topic.


        1. Chervin R. Idiopathic Hypersomnia. UpToDate. Waltham, MA: UpToDate; April 20, 2018; https://www.uptodate.com/contents/idiopathic-hypersomnia.
        2. Idiopathic Hypersomnia (IH) Standard Characteristics. Hypersomnia Foundation. October 4, 2017; https://www.hypersomniafoundation.org/wp-content/uploads/IH-Standard-Characteristics.pdf.
        3. What Treatments Are Available?. Hypersomnia Foundation. September, 2017; https://www.hypersomniafoundation.org/about-idiopathic-hypersomnia/.
        4. Idiopathic hypersomnia. MedlinePlus. April 12, 2017; https://medlineplus.gov/ency/article/000803.htm.
        5. Sowa NA. Idiopathic Hypersomnia and Hypersomnolence Disorder: A Systematic Review of the Literature. Psychosomatics. March-April 2016; 57(2):152-64. https://www.ncbi.nlm.nih.gov/pubmed/26895727.
        6. Trotti LM. Idiopathic Hypersomnia. Sleep Med Clin. September, 2017; 12(30:331-344. https://www.ncbi.nlm.nih.gov/pubmed/28778232.
        7. Saini P, Rye DB. Hypersomnia: Evaluation, Treatment, and Social and Economic Aspects. Sleep Med Clin. March, 2017; 12(1):47-60. https://www.ncbi.nlm.nih.gov/pubmed/28159097.

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