Hypersomnia is a condition characterized by extreme sleepiness during the day. It can also refer to a condition where someone spends an excessive amount of time sleeping. The person may not be able to stay awake at times when most people are awake. Hypersomnia can be dangerous. For example, someone with hypersomnia might fall asleep while driving.

Symptoms of hypersomnia can occur more frequently than people might expect. The National Sleep Foundation estimates that around 40 percent of people may have occasional symptoms of hypersomnia.

Learn more about this sleep disorder with the below hypersomnia related topics.