Idiopathic Hypersomnia

Excessive Sleepiness May Lack an Identifiable Cause

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If you have excessive daytime sleepiness without a clear explanation, you may have a condition called idiopathic hypersomnia. What is idiopathic hypersomnia? What conditions should be excluded before settling upon this diagnosis?

There are plenty of reasons to feel sleepy during the day. The most likely explanation is the simplest: not getting enough sleep. Everyone’s sleep needs differ, but if you get less than your body needs, you will be left feeling sleepy due to sleep deprivation.

When considering other potential causes of daytime sleepiness, the next major possibility is the presence of a sleep disorder that results in excessive sleepiness. Individuals with difficulties falling or staying asleep, or those who obtain adequate sleep but do not find it refreshing, may have insomnia. Disrupted breathing, such as occurs in sleep apnea, may lead to daytime sleepiness. Abnormal movements during sleep may also interrupt sound sleep, and conditions such as periodic limb movement syndrome may result in sleepiness. If the pattern of your sleep is misaligned to the night, as occurs in circadian rhythm sleep disorders, this might also lead to feeling sleepy.

In addition, excessive sleepiness is a key diagnostic feature of narcolepsy. It most often occurs in combination with loss of muscle tone in response to emotional stimuli (cataplexy), as well as with hypnagogic hallucinations and sleep paralysis.

Narcolepsy may also occur without cataplexy. People with narcolepsy fall asleep quickly, even during the day, and may experience rapid eye movement (REM) sleep during wakefulness. The disorder is characterized by difficulty staying asleep or awake, with rapid transitions between the states.

Certain psychiatric problems may also result in excessive sleepiness.

Most commonly, depression may disrupt sleep and lead to daytime sleepiness. People with depression may find themselves sleeping more or sleeping less. It is also common to have early-morning awakenings, often waking hours before the alarm clock sounds.

Many medications, both prescription and those sold over the counter, may have sleepiness or drowsiness as a side effect. You should review your medications with a doctor or pharmacist to see if these medicines might be contributing to you feeling sleepy.

Your doctor may choose to initiate a broader work-up to evaluate for other medical causes of sleepiness. It may useful to check your blood for abnormalities in thyroid stimulating hormone (TSH), a basic metabolic panel, and complete blood count. Depending on your specific health conditions, other tests may be warranted.

Sometimes sleep studies are undertaken to rule out the potential sleep disorders. It may be useful to track your sleep patterns over several weeks with actigraphy or a sleep diary.

A screening questionnaire called the Epworth sleepiness scale may quantify the severity of your sleepiness. An overnight sleep study called a polysomnogram may also be arranged. Further tests, such as multiple sleep latency testing (MSLT) or maintenance of wakefulness testing (MWT), may be warranted.

After careful evaluation and appropriate testing, the cause of your excessive sleepiness may not be apparent. A careful process of elimination may rule out common conditions that might cause excessive sleepiness, including those detailed above. When this occurs, in medical terms the condition is said to be "idiopathic" (of unknown cause). Furthermore, hypersomnia refers to the excessive sleepiness that characterizes the condition.

People with idiopathic hypersomnia report the ability to sleep for prolonged periods on a routine basis. There is evidence of excessive daytime sleepiness on the studies that are undertaken, including prolonged and highly efficient sleep without other abnormalities. Sometimes this is identified as a familial trait, suggesting that there may be a genetic component. It rarely represents a more episodic condition called Kleine-Levin syndrome. There is no specific diagnostic test beyond those meant to rule out other conditions, as described above.

As far as treatment of idiopathic hypersomnia, the mainstay is the use of stimulant medications. These medications are regulated as controlled substances and require a prescription. Commonly used stimulants include:

In addition, sufficient sleep and adherence to better sleep guidelines may also be advocated. Unfortunately, there may be a lack of response to therapy and symptoms of excessive sleepiness can be difficult to control. Safety measures, including driving restriction, may also be advisable.

If you feel that you are more tired during the day than you should be, you should start by speaking with your doctor. After discussing the matter, further testing may be pursued to identify an explanation. However, if no cause can be found, you might conclude that your excessive sleepiness is due to idiopathic hypersomnia.


Durmer, J.S. et al. "Pediatric Sleep Medicine." Continuum Lifelong Learning Neurol 2007;13(3):175-179.

Grossman, A. et al. "The maintenance of wakefulness test as a predictor of alertness in aircrew members with idiopathic hypersomnolence." Aviat Space Environ Med 2004;75(3):281-283.

Billiard, M. et al. "Idiopathic hypersomnolence." Psychiatry Clin Neurosci 1998;52(2):125-129.

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