Narcolepsy

Narcolepsy is a condition that makes people very sleepy during the day and can cause them to fall asleep suddenly. Some people also have other symptoms, such as muscle weakness when they feel strong emotions.

The symptoms can have serious effects on daily life. People with narcolepsy have trouble staying awake for long periods of time. When narcolepsy causes a sudden loss of muscle tone, it is known as cataplexy (KAT-uh-plek-see). This can be triggered by a strong emotion, especially one that causes laughter.

Narcolepsy is divided into two types. Most people with type 1 narcolepsy have cataplexy. Most people with type 2 narcolepsy don't have cataplexy.

Narcolepsy is a lifelong condition and does not have a cure. However, medicines and lifestyle changes can help manage the symptoms. Support from family, friends, employers and teachers can help people cope with the condition.

The symptoms of narcolepsy may get worse during the first few years. Then they continue for life. Symptoms include:

• Extreme daytime sleepiness. Daytime sleepiness is the first symptom to appear, and the sleepiness makes it hard to focus and function. People with narcolepsy feel less alert and focused during the day. They also fall asleep without warning. Sleep can happen anywhere and at any time. It may happen when they are bored or while doing a task. For example, people with narcolepsy can suddenly fall asleep while working or talking with friends. It can be especially dangerous to fall asleep while driving. Sleep may last only a few minutes or up to a half-hour. After waking, people with narcolepsy feel refreshed but get sleepy again.
• Automatic behaviors. Some people with narcolepsy continue doing a task when they fall asleep briefly. For example, they may fall asleep while writing, typing or driving. They might continue to perform that task while asleep. After waking, they can't remember what they did, and they probably didn't do it well.
• Sudden loss of muscle tone. This condition is called cataplexy. It can cause slurred speech or complete weakness of most muscles for up to a few minutes. It's triggered by intense emotions — often positive emotions. Laughter or excitement may cause sudden muscle weakness. But sometimes fear, surprise or anger can cause the loss of muscle tone. For example, when you laugh, your head may drop without your control. Or your knees may suddenly lose strength, causing you to fall. Some people with narcolepsy experience only one or two episodes of cataplexy a year. Others have several episodes a day. Not everyone with narcolepsy has these symptoms.
• Sleep paralysis. People with narcolepsy may experience sleep paralysis. During sleep paralysis, the person can't move or speak while falling asleep or upon waking. The paralysis is usually brief — lasting a few seconds or minutes. But it can be scary. You may be aware of it happening and can recall it afterward. Not everyone with sleep paralysis has narcolepsy.
• Hallucinations. Sometimes people see things that aren't there during sleep paralysis. Hallucinations also may happen in bed without sleep paralysis. These are called hypnagogic hallucinations if they happen as you fall asleep. They're called hypnopompic hallucinations if they happen upon waking. For example, the person might think they see a stranger in the bedroom who isn't there. These hallucinations may be vivid and frightening because you may not be fully asleep when you begin dreaming.
• Changes in rapid eye movement (REM) sleep. REM sleep is when most dreaming happens. Typically, people enter REM sleep 60 to 90 minutes after falling asleep. But people with narcolepsy often move more quickly to REM sleep. They tend to enter REM sleep within 15 minutes of falling asleep. REM sleep also can happen at any time of the day.

The exact cause of narcolepsy is not known. People with type 1 narcolepsy have low levels of hypocretin (hi-poe-KREE-tin), also called orexin. Hypocretin is a chemical in the brain that helps control being awake and entering REM sleep.

Hypocretin levels are low in people who have 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. An autoimmune reaction is when the body's immune system destroys its own cells.

It's also likely that genetics plays a role in narcolepsy. But the risk of a parent passing this sleep condition to a child is very low — only about 1% to 2%.

Narcolepsy may be linked to exposure to the H1N1 flu, sometimes called the swine flu. It also may be linked to a certain type of the H1N1 vaccine that was given in Europe.

There are only a few known risk factors for narcolepsy, including:

• Age. Narcolepsy typically begins between ages 10 and 30.
• Family history. Your risk of narcolepsy is 20 to 40 times higher if you have a close family member who has it.

Narcolepsy can cause complications, such as:

• Misbeliefs about the condition. Narcolepsy can affect work, school or your personal life. Others might see people with narcolepsy as lazy or sluggish.
• Effects on intimate relationships. Intense feelings, such as anger or joy, can trigger cataplexy. This can cause people with narcolepsy to withdraw from emotional interactions.
• Physical harm. Falling asleep suddenly may result in injury. You're at increased risk of a car accident if you fall asleep while driving. Your risk of cuts and burns is greater if you fall asleep while cooking.
• Obesity. People with narcolepsy are more likely to be overweight. Sometimes weight goes up quickly when symptoms start.