Despite feeling tired and sleepy during the day, many people with narcolepsy have trouble sleeping at night. They wake up frequently (also called “fragmented” sleep), and have a hard time falling back to sleep. The reason for this is not completely understood, but sleep research suggests people with narcolepsy have more light sleep and more transitions out of deep sleep into light sleep or awake.
In the case of narcolepsy, poor nighttime sleep is not enough to explain daytime sleepiness. A person with narcolepsy can feel very tired and sleepy during the day regardless of how well they slept the night before.