Glossary

Rapid eye movement sleep; normally occurs at night and includes dreams. Most muscles are not active to prevent people from acting out their dreams.

Also often called narcolepsy with cataplexy. People with type 1 narcolepsy can be diagnosed by their cataplexy or, if measured, by low levels of hypocretin (also known as orexin).

Also called narcolepsy without cataplexy. The cause of type 2 narcolepsy is unknown.

A state of sleep made up of different stages, from light sleep to deep sleep. Deep stages help to restore the body. People usually wake up more easily from light non-REM sleep than from deep non-REM sleep.

Daytime and evening habits and routines to help improve sleep.

Brief total loss of control of voluntary muscles when people are typically fully aware of what is going on around them. Occurs when falling asleep or while waking up, and can be frightening.

Also known as orexin, hypocretin is a naturally occurring chemical in the brain that helps maintain wakefulness and prevent non-REM sleep and REM sleep from occurring at the wrong time. Low levels of hypocretin cause the separate states of wakefulness and sleep to not work properly, shifting often from one state to another, leading to symptoms of narcolepsy.

Unintentionally falling asleep due to excessive daytime sleepiness. Also known as “sleep attacks.”

The inability to stay awake and alert during the day, resulting in a constant and uncontrollable need for sleep or unintentionally falling asleep. The primary symptom of narcolepsy.

A naturally occurring chemical in the brain that helps maintain wakefulness. When histamine activity in the brain is high, people are typically awake.

Many people with narcolepsy have vivid dream-like experiences while falling asleep, called hypnagogic hallucinations. Hypnopompic hallucinations are similar experiences but they occur while waking up.

Frequent shifts between different states of sleep and wakefulness that occur at night, causing poor quality sleep. These disruptions significantly decrease restorative sleep stages.

Complete collapse to the ground; usually takes several seconds to develop and many muscle groups are involved.

Only certain muscle groups are involved; facial, head, or neck weakness is common.

A commonly used phrase to describe difficulty focusing or concentrating; confusion.

Cataplexy is the muscle weakness of REM sleep occurring during wakefulness. People living with narcolepsy experience cataplexy as a sudden and brief loss of muscle strength or tone (e.g., knees buckling, jaw sagging) with retained awareness, often triggered by strong emotions. Narcolepsy with cataplexy is known as type 1 narcolepsy.

Performance of routine tasks (e.g., writing, cooking) without awareness or memory.