Narcolepsy is a chronic, neurological disorder that affects the control of sleep and wakefulness. It causes fragmented night sleep and excessive daytime sleepiness.
It also features abnormal rapid eye movement (REM) sleep and it can involve cataplexy, brief attacks of muscle weakness and tone that can lead to body collapse.
Narcolepsy can range in severity from mild to severe. In severe cases, it can negatively impact social activities, school, work, and overall health and well-being. A person with narcolepsy may fall asleep at any time, for example, while talking or driving.
Symptoms tend to appear in the teenage years, or early twenties and thirties. Men and women are equally susceptible, and it is thought to affect 135,000 to 200,000 people in the United States at any one time.
Fast facts on narcolepsy
Here are some key points about narcolepsy. More detail is in the main article.
Around 1 in 2,000 people in the United States have narcolepsy.
The main symptoms are excessive daytime sleepiness and abnormal rapid eye movement (REM) sleep.
Narcolepsy is the second leading cause of excessive daytime sleepiness after obstructive sleep apnea.
Symptoms typically begin between the ages of 10 and 30 years.
Narcolepsy can be treated with medications and lifestyle adjustments.
What is narcolepsy?
A person with narcolepsy can fall asleep at any time, often without warning.
Narcolepsy is a considered a hypersomnia, or a sleep disorder characterized by excessive daytime sleepiness.
In a typical sleep cycle, a person enters the early stage of sleep, followed by deeper sleep stages for 90 minutes where finally REM sleep occurs.
For people with narcolepsy, REM sleep occurs within 15 minutes in the sleep cycle, and intermittently during the waking hours. It is in REM sleep that dreams and muscle paralysis occur.
There are three types of narcolepsy:
Type 1: Narcolepsy with cataplexy
Type 2: Narcolepsy without cataplexy, which mainly involves excessive daytime sleepiness
Secondary narcolepsy: This can result from an injury to the hypothalamus, a part of the brain involved in sleep.
The exact cause is unknown, but narcolepsy may be an inherited autoimmune disease that leads to a deficiency in hypocretin, or orexin, a chemical the brain needs to stay awake. There may be a genetic disposition, which means it runs in families.
Hypocretin is a neurotransmitter, a nerve-signaling chemical. It controls whether we are asleep or awake by acting on different groups of nerve cells, or neurons in the brain. It is made in the hypothalamus region of the brain.
Most people with type 1 narcolepsy have low levels of this hormone, but those with type 2 do not.
Hypocretin is needed to help us stay awake. When it is not available, the brain allows REM sleep phenomena to intrude into normal waking periods. As a result, people with narcolepsy experience both excessive daytime sleepiness and nighttime sleeping problems.
In an autoimmune disorder, the body’s immune system mistakenly attacks itself and fights off healthy cells as if they were foreign invaders. Other autoimmune diseases include rheumatoid arthritis, type 1 diabetes, and celiac disease.
A brain injury, tumor, or other disease that affects the brain can sometimes lead to narcolepsy.
Everything you need to know about cataplexy
Learn more about cataplexy
Sleep paralysis is a brief inability to move or speak while falling asleep or waking up. These episodes can last from a few seconds to several minutes. After the episode ends, people rapidly recover their full capacity to move and speak.
Automatic behaviors can also occur. A person may fall asleep momentarily but continue doing the previous activity, such as driving, without being conscious.