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Idiopathic Hypersomnia without Long Sleep Time

What is it?

Idiopathic hypersomnia without long sleep time is one of the disorders of severe sleepiness. It causes you to have disabling daytime sleepiness. This occurs despite a normal or an increased nightly sleep time. Your nightly sleep time ranges from 8 to10 hours.

Other people may also have these same symptoms, except they sleep longer than 10 hours nightly. They have idiopathic hypersomnia with long sleep time.

People with this disorder may sleep from 8 to 10 hours every night with few interruptions. Even after sleeping all night, it is very hard to awaken. You may set many alarms and still have trouble waking up.

Once you awaken, you may appear to be partially asleep, confused or drunk. This is called sleep drunkenness. Confusion and sleep drunkenness are common after morning awakening and also after naps. Naps can be long, but they are not refreshing. No matter how much sleep you get, you are still sleepy.

School, jobs and relationships often suffer because of the long hours of sleep and the disabling sleepiness. You may appear to stare blankly. You also may appear to forget doing simple activities. Some people with this disorder experience these problems:

  • Headaches
  • Dizziness
  • Cold hands and feet
  • Depression symptoms

This disorder can make you even sleepier than someone who has narcolepsy. But daytime sleepiness can be more severe with narcolepsy. Naps can be refreshing to someone with narcolepsy. With idiopathic hypersomnia, naps are often longer and are not refreshing.

Some people with idiopathic hypersomnia have symptoms that resemble narcolepsy. Examples are sleep paralysis and hallucinations. But people with idiopathic hypersomnia do not have the symptom of cataplexy, which is a sudden attack of muscle weakness. They also do not have as many episodes of quickly entering REM sleep as someone with narcolepsy.

There is also a distinct difference between true sleepiness and disabling fatigue. People with fatigue caused by depression or a medical disorder may feel very tired. An example is when someone has chronic fatigue syndrome. But people with fatigue do not fall sleep uncontrollably or for long periods of time. This separates them from people who have idiopathic hypersomnia without long sleep time.

Who gets it?

Idiopathic hypersomnia without long sleep time tends to start slowly before the age of 30. It is severe and disabling and usually does not change over time. There have been a few cases when it improved unexpectedly.

It is rare and less common than narcolepsy. It is even rarer for children to have it. Men and women seem to have it equally. It does seem to run in families, but no gene has been identified.

How do I know if I have it?

  1. Are you very sleepy even though you sleep 8 to 10 hours nightly without interruption? Has this been occurring daily and nightly for more than three months?

  2. Are you very sleepy even after napping, in addition to sleeping 8 to 10 hours nightly? Are these naps unrefreshing?

  3. You do NOT have narcolepsy symptoms such as cataplexy.

  4. Your sleepiness can NOT be explained by any of the following:

  • Other sleep disorders such as sleep apnea, restless legs syndrome, periodic limb movement disorder, or narcolepsy

  • Other medical, neurological, or psychiatric conditions

  • The use of alcohol, medications, or drug abuse

If your answer to all of these questions is yes, then you might have idiopathic hypersomnia without long sleep time.

Do I need to see a sleep specialist?

Idiopathic hypersomnia without long sleep time is a chronic and potentially dangerous disorder. This is because it involves disabling sleepiness. Driving may be dangerous. School, work and relationships are often affected because you spend so many hours sleeping and remain very sleepy.

It is important to make sure there is not another reason for the sleepiness. It could be related to another sleep, medical, neurological or psychiatric disorder. You are strongly advised to seek a doctor’s advice.

What will the doctor need to know?

The doctor should ask you about your medical, neurologic and sleep symptoms. The doctor also should ask you about your medications, alcohol use and family history. The doctor should do a thorough exam. This should include a complete neurologic exam.

You may be asked to complete a sleep diary to monitor your progress before and after treatment. A sleep diary helps to show how many hours you are sleeping and when you are sleeping and napping. A sleep diary can also reveal signs of other sleep disorders that may be present. For example, the diary may point to a circadian rhythm disorder if it shows that you sleep earlier or later than normal.

You will be asked to rate your sleep with the Epworth Sleepiness Scale. This will help show how your sleep is affecting your daily life. Be sure to inform the doctor of any past or present drug, alcohol and medication use. Also tell the doctor if you have ever had any other sleep disorder. Your doctor will likely ask you to see a sleep specialist.

Will I need to take any tests?

There is a good chance your doctor will perform blood and urine drug testing. This will make sure your sleepiness is not from medication or drug use.

You will be asked to do extended sleep studies that last all night and then all the next day. The first part of the sleep study is an overnight sleep study. This is called a polysomnogram. The polysomnogram charts your brain waves, heart beat, muscle activity and breathing as you sleep. It also records how your arms and legs move.

This shows if there are other disorders that are causing or increasing your sleep problems. Examples include sleep apnea and periodic limb movement disorder. The best sleep study will also record your sleep on video. This will help show if you get out of the bed and do anything unusual during the study.

After the overnight sleep study, sleep testing will continue with a daytime sleep study. This is called a Multiple Sleep Latency Test, or MSLT. This test is a series of daytime nap opportunities. This same test is also used to see if someone has narcolepsy. Meals are usually provided at normal times during the day. You should expect to stay until late afternoon or early evening.

How is it treated?

The causes of idiopathic hypersomnia without long sleep time are currently unknown. Treatment focuses on relieving the symptom of sleepiness. This disorder is treated with many of the same medications used for narcolepsy. People with narcolepsy often respond to the medications better than people with idiopathic hypersomnia.

Follow these tips as a part of your treatment program:

  • Keep regular sleep times. Plan to take the medications when you will need to be alert and active. If you are sleepy, then you should not drive.

  • Avoid certain medications that may affect sleep and sleepiness. Also avoid alcohol.

  • Treat any and all other sleep disorders that are present. Treat any other medical or psychiatric conditions.

  • Have a doctor monitor your progress as you undergo ongoing treatment.



    By Sharon L. Schutte-Rodin, MD
    Updated on January 12, 2006


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