Idiopathic Hypersomnia

What it feels like

People with IH often describe:

• constant daytime sleepiness and a need to nap, sometimes for hours
• sleeping 10 to 12 hours or more at night and still feeling tired
• sleep inertia (sleep drunkenness): extreme difficulty waking up, sleeping through alarms, and feeling confused, clumsy, irritable or disoriented for a prolonged time after waking
• naps that are long and unrefreshing, unlike the short, refreshing naps typical of narcolepsy
• brain fog: poor memory, attention and concentration
• automatic behaviors: doing routine tasks without remembering them

Many also have headaches, feeling cold, dizziness on standing and depression, the latter often from the burden of the condition.

Causes

The cause is unknown. Research has explored increased activity of the brain's GABA system, which promotes sleep, and differences in circadian rhythm. It sometimes runs in families. IH is not caused by laziness or poor sleep habits.

Idiopathic hypersomnia vs narcolepsy

Other causes that must be ruled out

• insufficient sleep or irregular schedules
• obstructive sleep apnea
• delayed sleep phase disorder
• depression and other psychiatric conditions
• medicines (sedating antihistamines, some antidepressants, antipsychotics, opioids) and substance use
• hypothyroidism, anemia, head injury and other medical conditions
• Kleine-Levin syndrome, which causes episodes of extreme sleepiness rather than constant sleepiness

Diagnosis

A sleep specialist will take a detailed history, often with a 1 to 2 week sleep diary or actigraphy (a wrist activity monitor). Tests include:

• Overnight polysomnography: rules out sleep apnea and other sleep disruptions.
• Multiple sleep latency test (MSLT): the next day, you take 4 to 5 scheduled naps. IH is supported by falling asleep in an average of 8 minutes or less, with fewer than 2 episodes of REM sleep.
• Extended 24-hour sleep monitoring: total sleep of 11 hours or more in 24 hours also supports IH, and is useful because some people with IH do not meet the MSLT criteria.

Symptoms must be present for at least 3 months. Blood tests may check thyroid function, iron and other causes.

Treatment

There is no cure, but treatment improves alertness and daily function:

• Low-sodium oxybate: the first medicine FDA-approved specifically for IH in adults, taken at night.
• Modafinil or armodafinil: wake-promoting agents commonly used off-label.
• Stimulants: such as methylphenidate or amphetamines.
• Other options: pitolisant, solriamfetol, and in some people clarithromycin or flumazenil, which affect GABA signaling, under specialist guidance.

Lifestyle measures

• keep a regular sleep schedule, including weekends
• use multiple alarms, light-up alarm clocks, or a family member's help on waking; schedule demanding tasks for when you are most alert
• avoid alcohol and sedating medicines
• discuss accommodations at school or work, such as later start times or flexible hours
• do not drive when sleepy

Outlook

IH is usually lifelong, though symptoms improve in some people over years. With treatment and accommodations, many people manage school, work and family life. Support groups can help with the emotional impact.

Frequently asked questions

What is idiopathic hypersomnia?

It is a chronic sleep disorder that causes excessive daytime sleepiness despite normal or long night sleep, often with very long, unrefreshing naps and severe difficulty waking up. The cause is unknown, which is what "idiopathic" means.

What is sleep drunkenness?

Sleep drunkenness, or severe sleep inertia, is prolonged confusion, clumsiness, irritability and grogginess after waking. People may sleep through many alarms. It is a hallmark of idiopathic hypersomnia and can last from many minutes to hours.

How is idiopathic hypersomnia different from narcolepsy?

Both cause excessive sleepiness. In IH, night sleep is long and deep, naps are long and unrefreshing, and waking is very hard. In narcolepsy, naps are short and refreshing, night sleep is often broken, and type 1 includes cataplexy. Sleep studies help tell them apart.

Is idiopathic hypersomnia treatable?

Yes. Medicines such as low-sodium oxybate, modafinil and stimulants improve alertness for many people. Regular sleep schedules, strategies for waking, and school or work accommodations also help.