What Is Idiopathic Hypersomnia?

Reviewed by: HU Medical Review Board | Last reviewed: May 2021

Idiopathic hypersomnia (IH) is a chronic sleep disorder that causes excessive daytime sleepiness. Symptoms usually begin in teenagers or young adults and can develop over weeks or months. Unlike narcolepsy, when people with IH take daytime naps, it does not improve their symptoms.1

What causes idiopathic hypersomnia?

Doctors do not yet know what causes IH. Some people with IH have a family history of sleeping disorders. This could be a sign that genetics play a role in IH. A different theory is that people with IH overproduce a molecule that impacts brain functions that control sleep.1,2

However, neither of these theories has been proven. More research is needed to understand the causes of IH.1,2

Symptoms of idiopathic hypersomnia

The main symptom of IH is excessive daytime sleepiness despite getting enough sleep at night. This can mean having difficulty staying awake during the day. It may also cause other symptoms like:1,2

  • Taking long naps but waking up unrefreshed
  • Regularly sleeping more than 11 hours at night
  • Brain fog or problems with memory, attention, and concentration

People with IH often have trouble waking up in the morning or after naps. This may cause needing many alarms to wake up. Many people may also experience “sleep drunkenness.” This is the name for extreme difficulty feeling fully awake and the strong urge to go back to sleep. Sleep drunkenness can last a few hours. It can cause confusion, irritability, feeling disoriented, and bad coordination.2

Other symptoms linked to IH include:1

Severe IH can impact many aspects of peoples’ lives. It can impact their abilities to maintain a job or social life. It can also negatively impact personal relationships.2

How is idiopathic hypersomnia diagnosed?

IH is diagnosed by ruling out other causes of sleepiness if symptoms have been present for more than 3 months. Other causes could be more common sleep disorders, medicines, or not enough sleep.2

Your doctor may use tests to diagnose your condition. These tests may include:2,3

  • Overnight sleep test (polysomnogram) – This test happens at a sleep center, where you are hooked up to a machine called a polysomnogram. The polysomnogram monitors your brain activity, body movements, heart rate, and oxygen levels as you sleep.
  • Multiple sleep latency test (MSLT) – This test usually happens the day after your polysomnogram. A MSLT measures how long it takes you to fall asleep for a nap during the day. The time it takes to fall asleep is called your sleep latency.

You may also be asked to keep a sleep diary. A sleep diary is a record you keep of your sleeping habits over a few weeks. You would be asked to record information like when you go to sleep and wake up. Your doctor can use this information to understand your sleep patterns.3

Your doctor will use the results from your tests, sleep diary, and medical history to make a diagnosis.2,3

Treatments for idiopathic hypersomnia

IH does not have a cure, and treatment is focused on controlling symptoms and lowering sleepiness. There are not yet any approved treatments specifically for IH. IH is usually treated with drugs that are approved to treat narcolepsy. This is called off-label use.1

Of the drugs approved for narcolepsy, IH is typically treated with stimulants. Some examples include:1

  • Modafinil (Provigil)
  • Armodafinil (Nuvigil)
  • Amphetamines (Adderall)
  • Methylphenidate (Ritalin)

However, since these drugs are not designed to treat IH, they often do not work as well for people with IH as they do for those with narcolepsy. They often do not control symptoms well enough. Also, they sometimes stop working over time as users develop a resistance.2

There are other steps people with IH can take that may improve their symptoms. These include lifestyle and behavior changes.2,3

Behavioral approaches, like cognitive behavioral therapy (CBT), can be helpful. CBT is a goal-oriented therapy. It focuses on changing behaviors and thought patterns. It may help people with IH cope with their condition.2,3

Lifestyle changes may also reduce symptoms of IH. They include things like avoiding alcohol and practicing a regular nighttime routine.2,3

There is still much that we do not know about IH. More research is needed to develop better treatments and understanding of IH.

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