Which sleep disorder involves an irresistible compulsion to sleep during the day?

Narcolepsy is characterized by an irresistible compulsion to sleep during the day, often leading to sudden, uncontrollable episodes of sleep. Individuals with this disorder may experience excessive daytime sleepiness even after a full night's sleep and can fall asleep at inappropriate times, such as during work or conversations. This is distinct from other sleep disorders, where the primary issues differ.

For instance, insomnia primarily involves difficulty in falling or staying asleep, resulting in inadequate sleep, but does not inherently include sudden daytime sleepiness. Sleep apnea involves disruptions in breathing during sleep, which leads to fragmented sleep and excessive daytime fatigue but is not directly about an overwhelming urge to sleep. Restless leg syndrome is marked by uncomfortable sensations in the legs and an urge to move them, particularly during restful periods, which can lead to difficulties in falling asleep, but does not cause the sudden sleep episodes characteristic of narcolepsy. Thus, narcolepsy is the only option listed that specifically describes this daytime sleep compulsion, making it the correct answer.