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Frequently asked questions about
Idiopathic Hypersomnia (IH)

IH is classified in the International Classification of Sleep Disorders, 3rd Edition (ICSD-III), as a central disorder of hypersomnolence with distinct diagnostic criteria and clinical features, including excessive daytime sleepiness (), , cognitive impairment, long unrefreshing naps and prolonged sleep time. There are other key symptoms of IH to look out for when making a diagnosis.1
see key symptoms

In the US, approximately 37,000 adult patients have been diagnosed with IH and are actively seeking medical care. It is estimated that far fewer people are currently receiving pharmacological treatment for their IH. This low number of people may be due to the many difficulties in identifying and diagnosing IH, as well as distinguishing it from other similar sleep disorders.2

When comparing the ICSD-III diagnostic criteria of IH with other sleep disorders, several key differences are evident and there are specific diagnostic criteria for IH you can use.1

According to the International Classification of Sleep Disorders, 3rd Edition (ICSD-III), an IH diagnosis must meet all of the following criteria1:

  • Excessive daytime sleepiness () for ≥3 months
  • <2 (or no SOREMPs if latency on preceding is ≤15 minutes)
  • Absence of
  • Presence of at least 1 of the following:
    • The multiple sleep latency test () shows a mean sleep latency () of ≤8 minutes
    • Total 24-hour sleep time is ≥660 minutes (typically 12 to 14 hours) on either 24-hour monitoring or a ≥7-day average of wrist actigraphy
  • Insufficient sleep syndrome is ruled out
  • Hypersomnolence and/or findings are not better explained by other causes

There are steps you can take to confidently diagnose IH.

Although the exact cause of IH is unknown, several pathophysiological mechanisms have been proposed. Changes in sleep architecture may also be a contributor.3

Recent findings are helping to partially explain the non-restorative sleep experienced by patients with IH.

Profound upon waking from sleep, also referred to as “sleep drunkenness”, can be the main complaint of patients living with IH. Sleep inertia has been described as4,5:
  • A severe inability to wake up in the morning
  • Feeling caught between sleep and wake states
  • Lasting minutes to several hours
  • Feeling confused, uncoordinated, or even aggressive
  • Suffering from impaired performance and reduced vigilance
can have a real impact on patients with IH.4

IH can have unexpected and dangerous consequences for personal safety and public health.6

There's an FDA-approved treatment that may be right for your patients.


  1. American Academy of Sleep Medicine. International Classification of Sleep Disorders. 3rd ed. Darien, IL: American Academy of Sleep Medicine; 2014.
  2. Data on File (XYW-2021-025-28). Jazz Pharmaceuticals, Inc.
  3. Plante DT. Nocturnal sleep architecture in idiopathic hypersomnia: a systematic review and meta-analysis. Sleep Med. 2018;45:17-24.
  4. Trotti LM. Waking up is the hardest thing I do all day: sleep inertia and sleep drunkenness. Sleep Med Rev. 2017;35:76-84.
  5. Arnulf I, Leu-Semenescu S, Dodet P. Precision medicine for idiopathic hypersomnia. Sleep Med Clin. 2019;14(3):333-350.
  6. Pizza F, Jaussent I, Lopez R, et al. Car crashes and central disorders of hypersomnolence: a French study. PLoS One. 2015;10(6):e0129386.

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