The symptoms of narcolepsy most commonly begin between the ages of 10 and 25. They may worsen for the first few years, and then continue for life. They include:
Excessive daytime sleepiness. People with narcolepsy fall asleep without warning, anywhere, anytime. For example, you may suddenly nod off while working or talking with friends. You may sleep for a few minutes or up to a half-hour before awakening and feeling refreshed, but eventually you fall asleep again.
You also may experience decreased alertness throughout the day. Excessive daytime sleepiness usually is the first symptom to appear and is often the most troublesome, making it difficult for you to concentrate and fully function.
Sudden loss of muscle tone. This condition, called cataplexy (KAT-uh-plek-see), can cause a number of physical changes, from slurred speech to complete weakness of most muscles, and may last for a few seconds to a few minutes.
Cataplexy is uncontrollable and is triggered by intense emotions, usually positive ones such as laughter or excitement, but sometimes fear, surprise or anger. For example, your head may droop uncontrollably or your knees may suddenly buckle when you laugh.
Some people with narcolepsy experience only one or two episodes of cataplexy a year, while others have numerous episodes daily. Not everyone with narcolepsy experiences cataplexy.
Sleep paralysis. People with narcolepsy often experience a temporary inability to move or speak while falling asleep or upon waking. These episodes are usually brief — lasting one or two minutes — but can be frightening. You may be aware of the condition and have no difficulty recalling it afterward, even if you had no control over what was happening to you.
This sleep paralysis mimics the type of temporary paralysis that normally occurs during rapid eye movement (REM) sleep, the period of sleep during which most dreaming occurs. This temporary immobility during REM sleep may prevent your body from acting out dream activity.
Not everyone with sleep paralysis has narcolepsy, however. Many people without narcolepsy experience some episodes of sleep paralysis, especially in young adulthood.
- Hallucinations. These hallucinations are called hypnagogic hallucinations if occurring as you fall asleep and hypnopompic hallucinations if occurring upon waking. Because you may be semi-awake when you begin dreaming, you experience your dreams as reality, and they may be particularly vivid and frightening
People with narcolepsy may have other sleep disorders, such as obstructive sleep apnea, a condition in which breathing starts and stops throughout the night, restless legs syndrome and even insomnia. People with narcolepsy may also act out their dreams at night by flailing their arms or kicking and screaming.
Some episodes of sleep attacks are brief, lasting seconds. Some people with narcolepsy experience automatic behavior during these brief episodes. For example, you may fall asleep while performing a task you normally perform, such as writing, typing or driving, and you continue to function while asleep. When you awaken, you can't remember what you did, and you probably didn't do it well.
When to see a doctor
See your doctor if you experience excessive daytime sleepiness that disrupts your personal or professional life.
The exact cause of narcolepsy isn't known. Genetics may play a role. Other factors, such as infection, may contribute to the development of narcolepsy.
Normal sleep pattern vs. narcolepsy
The normal process of falling asleep begins with a phase called non-rapid eye movement (NREM) sleep. During this phase, your brain waves slow considerably. After an hour or so of NREM sleep, your brain activity changes, and REM sleep begins. Most dreaming occurs during REM sleep.
In narcolepsy, however, you may suddenly enter into REM sleep without first experiencing NREM sleep, both at night and during the day. Some of the characteristics of REM sleep, such as sudden lack of muscle tone, sleep paralysis and vivid dreams, occur during other sleep stages in people with narcolepsy.
The role of brain chemicals
Hypocretin (hi-po-KREE-tin) is an important chemical in your brain that helps regulate wakefulness and REM sleep. People with narcolepsy have low levels of this neurochemical in their spinal fluid. It's particularly low in those who experience cataplexy. Exactly what causes the loss of hypocretin-producing cells in the brain isn't known, but experts suspect it's due to an autoimmune reaction.
Public misunderstanding of the condition
Narcolepsy may cause serious problems for you professionally and personally. Others might see you as lazy, lethargic or rude. Your performance may suffer at school or work.
Interference with intimate relationships
Extreme sleepiness may cause low sex drive or impotence, and people with narcolepsy may even fall asleep while having sex. The problems caused by sexual dysfunction can be further complicated by emotional difficulties. Intense feelings, such as anger or joy, can trigger some signs of narcolepsy such as cataplexy, causing affected people to withdraw from emotional interactions.
Sleep attacks may result in physical harm to people with narcolepsy. You're at increased risk of a car accident if you have an attack while driving. Your risk of cuts and burns is greater if you fall asleep while preparing food.
People with narcolepsy are twice as likely to be overweight. The weight gain may be related to inactivity, binge eating, hypocretin deficiency or a combination of factors.