Which condition is characterized by excessive daytime sleepiness?

The condition characterized by excessive daytime sleepiness is narcolepsy. This neurological disorder affects the brain's ability to regulate sleep-wake cycles, leading to severe daytime drowsiness and sudden episodes of sleep, known as sleep attacks. Individuals with narcolepsy may experience an overwhelming urge to sleep at inappropriate times, which significantly impacts their daily functioning.

Narcolepsy can also include other symptoms, such as cataplexy (sudden loss of muscle tone), sleep paralysis, and hallucinations during the transition between wakefulness and sleep. This combination of symptoms highlights how narcolepsy distinctly manifests as excessive daytime sleepiness, distinguishing it from other sleep disorders.

While sleep apnea can lead to daytime sleepiness due to disrupted sleep patterns, it is primarily characterized by breathing interruptions during sleep. Hypersomnia also involves excessive sleepiness but relates more broadly to excessive sleep duration rather than the sleep attacks that define narcolepsy. Insomnia, on the other hand, is characterized by difficulty falling or staying asleep, which typically does not lead to excessive daytime sleepiness as a primary symptom.