Idiopathic hypersomnia (IH) is a sleep disorder in which a person is excessively sleepy (hypersomnia) during the day and has great difficulty being awakened from sleep. Idiopathic means there is not a clear cause.
IH is similar to narcolepsy in that you are extremely sleepy. It is different from narcolepsy because IH doesn't usually involve suddenly falling asleep (sleep attacks) or losing muscle control due to strong emotions (cataplexy). Also, unlike narcolepsy, naps in IH are usually not refreshing.
Symptoms often develop slowly during the teens or young adulthood. They include:
- Daytime naps that do not relieve drowsiness
- Difficulty waking from a long sleep -- may feel confused or disoriented (''sleep drunkenness'')
- Increased need for sleep during the day -- even while at work, or during a meal or conversation
- Increased sleep time -- up to 14 to 18 hours a day
Other symptoms may include:
- Feeling irritated
- Loss of appetite
- Low energy
- Slow thinking or speech
- Trouble remembering
Exams and Tests
The health care provider will ask about your sleep history. The usual approach is to consider other possible causes of excessive daytime sleepiness.
Other sleep disorders that may cause daytime sleepiness include:
Other causes of excessive sleepiness include:
Tests that may be ordered include:
- Multiple-sleep latency test (a test to see how long it takes you to fall asleep during a daytime nap)
- Sleep study (polysomnography, to identify other sleep disorders)
A mental health evaluation for depression may also be done.
Your provider will likely prescribe stimulant medicines such as amphetamine, methylphenidate, or modafinil. These drugs may not work as well for this condition as they do for narcolepsy.
Lifestyle changes that can help ease symptoms and prevent injury include:
- Avoid alcohol and medicines that can make the condition worse
- Avoid operating motor vehicles or using dangerous equipment
- Avoid working at night or social activities that delay your bedtime
When to Contact a Medical Professional
Discuss your condition with your provider if you have repeated episodes of daytime sleepiness. They may be due to a medical problem that needs further testing.
Hypersomnia - idiopathic; Drowsiness - idiopathic; Somnolence - idiopathic
Billiard M, Sonka K. Idiopathic hypersomnia. Sleep Med Rev. 2016;29:23-33. PMID: 26599679 www.ncbi.nlm.nih.gov/pubmed/26599679.
Dauvilliers Y, Bassetti CL. Idiopathic hypersomnia. In: Kryger M, Roth T, Dement WC, eds. Principles and Practice of Sleep Medicine. 6th ed. Philadelphia, PA: Elsevier; 2017:chap 91.
Review Date 4/8/2019
Updated by: Allen J. Blaivas, DO, Division of Pulmonary, Critical Care, and Sleep Medicine, VA New Jersey Health Care System, Clinical Assistant Professor, Rutgers New Jersey Medical School, East Orange, NJ. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.