August 2020 | Reviewed by: Anne M. Morse, DO and Andrea Matsumura, MD
What is narcolepsy?
Narcolepsy is a lifelong neurologic disorder that is characterized by the inability to control normal sleep wake cycles. Individuals with narcolepsy feel overwhelmingly tired, and in some cases, can have sudden episodes of muscle weakness. Narcolepsy can impact nearly every aspect of your life. It is dangerous because you may experience excessive sleepiness or a loss of muscle tone at any time of the day. These can happen in the middle of any activity including eating, walking or driving. Operating a vehicle with untreated narcolepsy can be very dangerous and some states even have laws against it.
Many people with narcolepsy do not know they have the sleep disorder. About one in 2,000 people have some form of narcolepsy. However, it is thought that about 50% of patients with narcolepsy may be undiagnosed and therefore the prevalence may be underestimated. Pediatric onset is common, as is a delay in diagnosing the disorder. The average delay in diagnosis is 8 to 10 years. Narcolepsy may run in some families, but most cases are not genetic.
When you add up the hours of total sleep time, people with narcolepsy don’t necessarily sleep any more than people who don’t have narcolepsy. This is especially true when you consider that many people with narcolepsy often have difficulty sleeping through the night because of unwanted awakenings.
Some people think because they are consistently tired during the day that they may have narcolepsy. Other sleep disorders that cause daytime sleepiness are often mistaken for narcolepsy. These include sleep apnea, circadian rhythm disorders, and restless legs syndrome. Medical conditions, mental health disorders, and use of certain medications or substances can also cause symptoms similar to narcolepsy
There are two types of narcolepsy:
Narcolepsy type 1
This type of narcolepsy involves a combination of excessive daytime sleepiness and one or both of the following:
- Sudden loss of muscle tone or episodes of muscle weakness while you are awake are known as cataplexy. It may lead to slurred speech and buckling knees, or in more severe cases complete paralysis. These events are usually triggered by strong emotions such as joy, surprise, laughter or anger.
- Low or absent CSF hypocretin-1 levels. Narcolepsy type 1 is caused by a deficiency of the neurotransmitter hypocretin (orexin). Hypocretin is a chemical that regulates arousal, wakefulness and appetite. A patient with low hypocretin has narcolepsy type 1, even if they don’t exhibit cataplexy.
Narcolepsy type 2
This type of narcolepsy occurs when you have excessive daytime sleepiness but no cataplexy. You may take a nap for a couple of hours and wake up feeling refreshed. But after a short time, you feel tired again.