hypersomnia

hypersomnia Excessive sleepiness in which a person has trouble staying awake during the day or exhibits prolonged nighttime sleep. People who have hypersomnia can fall asleep at any time—for example, at work or while they are driving—and they may have other sleep-related problems. Causes include narcolepsy, sleep deprivation, neurological or other medical conditions, obesity, genetic factors, medications, and drug or alcohol abuse.