Which sleep disorder is characterized by uncontrollable episodes of falling asleep during the day?

The correct answer is narcolepsy, which is a neurological disorder characterized by excessive daytime sleepiness and uncontrollable episodes of falling asleep during the day. Individuals with narcolepsy often experience sudden sleep attacks, which can occur at any time and in various situations, such as while working, driving, or even during conversations. This condition can also include other symptoms, such as cataplexy (sudden muscle weakness triggered by strong emotions), sleep paralysis, and hypnagogic hallucinations.

Narcolepsy is distinct from sleep disorders like insomnia, which involves difficulty falling or staying asleep at night, leading to insufficient sleep rather than spontaneous daytime sleep episodes. Sleep apnea, on the other hand, is characterized by interruptions in breathing during sleep, resulting in fragmented sleep and excessive daytime sleepiness, but it does not specifically cause uncontrollable daytime sleep episodes. Sleepwalking involves performing complex behaviors while in a state of partial arousal during sleep, typically occurring in the night, and does not relate to daytime sleepiness.

Therefore, narcolepsy's unique feature of uncontrolled daytime sleep episodes makes it the correct answer in this context.