Which statement best defines hypersomnolence disorders?

• A. They involve excessive daytime sleepiness despite adequate nocturnal sleep
• B. They are characterized by insomnia with nocturnal awakenings
• C. They involve sleepwalking during the day
• D. They are defined by reduced REM sleep

Answer: (A)

Excessive daytime sleepiness despite adequate nighttime sleep is the defining feature of hypersomnolence disorders. The key idea is that people with these disorders experience persistent sleepiness during the day even when they have had enough or even more than enough sleep at night, leading to difficulties with alertness and performance, and often sudden sleep episodes or frequent naps. This helps distinguish hypersomnolence disorders from insomnia, where the primary issue is trouble initiating or maintaining sleep at night rather than daytime sleepiness after sufficient sleep. It also sets them apart from parasomnias like sleepwalking, which occur during sleep rather than reflecting daytime wakefulness. Reduced REM sleep is not the defining trait of these disorders, as REM architecture can vary and is not what characterizes hypersomnolence.