In the context of sleep disorders, what is hypersomnia?

Hypersomnia is characterized by excessive daytime sleepiness that occurs even after sufficient nighttime sleep. It can manifest as prolonged episodes of sleep that are difficult to awaken from, and individuals may struggle to stay awake during activities such as work or social interactions. This condition does not necessarily relate to the quantity of sleep obtained at night but rather to the quality of wakefulness during the day, making the experience of feeling overly sleepy during daylight hours the hallmark symptom.

The other options highlight different aspects of sleep-related issues: difficulty staying awake during the night refers to insomnia-like symptoms rather than hypersomnia, inability to maintain a regular sleep cycle pertains more to circadian rhythm disorders, and insomnia despite high levels of fatigue describes a situation where individuals find it hard to sleep even when they feel tired, a scenario that is not applicable to hypersomnia.