hy·​per·​som·​nia | \ ˌhī-pər-ˈsäm-nē-ə \

Definition of hypersomnia

: a disorder of sleep that is characterized by prolonged nocturnal sleep periods which typically occur at least three times a week, by sleep that is not restorative or refreshing, and by the presence of excessive daytime sleepiness

Note: Hypersomnia may occur secondary to a medical condition (such as sleep apnea or depression) or the use of certain medications or may arise spontaneously from an unknown cause.

The International Classification of Sleep Disorders defines idiopathic hypersomnia as a disorder of excessive sleepiness that is associated with major sleep episodes, the cause of which is presumed to lie in the central nervous system.— Sudhansu Chokroverty also : excessive daytime sleepiness not associated with disturbed nocturnal sleep : hypersomnolence Psychology Today reports that people who persistently fall asleep at their desks may be suffering from the dread hypersomnia— Curt Suplee

First Known Use of hypersomnia

1863, in the meaning defined above

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The first known use of hypersomnia was in 1863

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hy·​per·​som·​nia | \ -ˈsäm-nē-ə \

Medical Definition of hypersomnia

1 : sleep of excessive depth or duration
2 : the condition of sleeping for excessive periods at intervals with intervening periods of normal duration of sleeping and waking — compare narcolepsy

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