What is hypersomnolence disorder?

Updated: Oct 09, 2018
  • Author: Sufen Chiu, MD, PhD; Chief Editor: Caroly Pataki, MD  more...
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Hypersomnolence disorder as described in DSM-5 is the self-reported excessive need for sleep despite sleeping for at least 7 hours and having at least one of the following symptoms:

  • Recurrent periods of sleep or naps within the same day

  • A prolonged sleep of more than 9 hours per day that is not refreshing

  • Difficulty being fully awake after abrupt awakening

Individuals with hypersomnolence disorder usually fall asleep quickly and have good sleep efficiency (>90%). Despite this, they have sleep inertia/drunkenness, where they have difficulty waking up and appear confused, combative, or ataxic. They can also experience automatic behavior during which they carry out simple routines like driving, have no recall of going several miles, then realize they are several miles from where they thought they were. Naps are not refreshing despite lasting more than 1 hour. Individuals are at risk for autonomic nervous dysfunction such as recurrent vascular-type headaches, Raynaud phenomena, and fainting. The disorder usually begins in late adolescence, at a mean age of 17-24 years.

Hypersomnolence can be increased temporarily by stress and alcohol use. Viral infections have preceded or accompanied hypersomnolence in 10% of cases, sometimes several months after the infection. Head trauma can result in hypersomnolence within 6-18 months after injury. An autosomal dominant mode of inheritance occurs in a subset of familial cases.

Nocturnal PSG findings include normal-to-prolonged sleep duration, short sleep latency (< 8 min), normal-to-increased sleep continuity, and normal distribution of rapid eye movement (REM) sleep but increased amounts of slow-wave sleep. During naps, sleep-onset REM may be present but may occur less than 2 times in 4-5 nap opportunities.

Behaviorally induced insufficient sleep syndrome may produce symptoms of daytime sleepiness and resemble hypersomnolence disorder. Individuals with inadequate sleep "catch up" when they are free from social/academic/occupational demands. After 10-14 days of catch-up sleep, the diagnosis may be clearer.

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