Narcolepsy is a disorder affecting the regulation of the sleep/wake cycle. People with narcolepsy experience bouts of extreme daytime sleepiness and tend to fall asleep suddenly at inappropriate times. These “sleep attacks” seem to arise from an abrupt switch from wakefulness into REM sleep. The brain somehow skips the normal progression of sleep stages, entering into a dreamlike state immediately after a person lies down to sleep—or in the middle of daytime activities, such as talking, eating, or driving. Sudden muscle weakness (known medically as cataplexy) also may occur, causing a person to suddenly go limp or to fall.
The disorder affects about one in 2,000 people and usually appears between ages 15 to 30. It affects men and women equally and has a genetic component: having a close relative makes a person 20 to 40 times more likely to have it. On average, it takes five years of symptoms and visits to five physicians before a diagnosis of narcolepsy is made. This is because sleepiness may be the only symptom. If cataplexy occurs, it may be misdiagnosed as epilepsy or fainting.
In the late 1990s, researchers discovered that many cases of narcolepsy result from the lack of a brain chemical called hypocretin (also called orexin) that normally maintains wakefulness and helps regulate sleep. People with narcolepsy lose the cells that make hypocretin. The discovery of the gene that makes hypocretin and the location of its production in the brain has spurred research into new ways to diagnose and treat this disorder. Researchers have also found a link between narcolepsy and variations in a gene that controls immune function. They speculated that the loss of hypocretin-producing cells may stem from an autoimmune process, in which the body attacks itself.
Symptoms of narcolepsy
All people with narcolepsy are excessively sleepy and struggle to stay awake during the day, which often causes them to have great trouble completing tasks. In addition, they may have a number of other symptoms, most of which are manifestations of the REM sleep stage occurring during wakefulness. Most people have more than one but only rarely have all of the following additional symptoms.
Sleep attacks. A person may suddenly fall asleep for a few seconds to several minutes when relaxing or even while carrying on a conversation. These attacks may be more frequent when a person is doing something monotonous or repetitive. If REM sleep and dreaming occur immediately, the person sometimes makes conversation that is appropriate to the dream instead of the actual situation.
Cataplexy. A person may suddenly lose muscle tone while awake, causing the head to fall forward and the knees to buckle. Most attacks last for less than 30 seconds and may go unnoticed, but in severe cases, the person may fall and stay paralyzed for as long as several minutes. Laughter, anger, or other strong emotions often trigger cataplexy, which occurs when the brain mechanism that paralyzes muscles during REM sleep becomes activated.
Sleep paralysis. A terrifying feeling of paralysis may occur during the transition between wakefulness and sleep if the REM stage begins before a person is fully asleep. Although muscle control usually returns within a few minutes, episodes can cause great anxiety.
Hypnagogic hallucinations. When REM dreaming occurs during wakefulness, the vivid and often frightening images, known as hypnagogic hallucinations, are difficult to distinguish from reality. A person may see prowlers or believe that his or her house is on fire. This usually happens just at sleep onset or upon awakening. This condition can be confused with mental illness because its symptoms resemble those of some psychotic disorders.
Disturbed nighttime sleep. Just as sleep intrudes during the day, unwelcome awakenings can occur at night, depriving people with narcolepsy of restorative rest and worsening their daytime drowsiness. Some feel as if they have hardly slept at all.
Automatic behavior. Because of their profound exhaustion, people with narcolepsy perform many routine tasks without being fully aware of what they are doing. For example, one man washed and dried the dishes and then stacked them in the refrigerator, but he had no recollection of doing so.
Doctors suspect narcolepsy in people who are excessively sleepy with no other apparent cause, especially if the person also develops one of the other symptoms. Confirming the diagnosis requires an overnight and daytime sleep study. On the overnight study, the person typically falls asleep quickly, goes into REM sleep much faster than usual, and has no other sleep disorder that could cause sleepiness. The next day, the person undergoes a multiple sleep latency test: a series of five nap opportunities, spaced at two-hour intervals throughout the day.
A person with narcolepsy falls asleep very quickly and quickly enters REM sleep. Rested people without narcolepsy take longer to fall asleep during the naps or don’t sleep at all. If they do sleep, they don’t enter REM sleep in the short, 20-minute sleep period permitted during the test.
Treatments for narcolepsy
Treatment for narcolepsy is geared toward improving wakefulness during the day and preventing REM-related symptoms. The first-line drugs are two “wakefulness-promoting agents,” modafinil (Provigil) and armodafinil (Nuvigil), which are taken once a day in the morning. Exactly how these medications work isn’t clear, but they appear to boost levels of the neurotransmitter dopamine. Older drugs, including methylphenidate (Ritalin) or dextroamphetamine (Dexedrine) are less commonly prescribed because of their side effects, which include high blood pressure, anorexia (extreme weight loss), and addiction. Even with medications, however, people are never as alert as they would be if they didn’t have narcolepsy.
In most people, antidepressants that suppress REM sleep—such as fluoxetine (Prozac), sertraline (Zolo), paroxetine (Paxil), clomipramine (Anafranil), or venlafaxine (Effexor)—can also prevent cataplexy and other REM-related symptoms. Another medication for cataplexy is sodium oxybate (Xyrem), also known as gamma hydroxybutyrate (GHB). This medication helps decrease the number of cataplexy episodes and may improve nighttime sleep and reduce daytime sleepiness as well. Because of its chemical properties, it must be taken at bedtime and again during the middle of the night. Xyrem is tightly regulated because of its potential for misuse; it has been associated with criminal acts such as date rape.
Medications for Narcolepsy
|Generic name (brand name)||Use||Side effects, comments|
dextroamphetamine (Dexedrine, Adderall)
methylphenidate (Ritalin, Metadate, Concerta, others)
|To counter daytime sleepiness||Nervousness, insomnia, loss of appetite, nausea, dizziness, irregular heartbeat, headaches, changes in blood pressure and pulse, weight loss. Potential for abuse. Should not be used by people who take monoamine oxidase inhibitors (MAOIs) or who have glaucoma.|
|To counter daytime sleepiness||Anxiety, headache, nausea, nervousness, insomnia. Less potential for abuse than other stimulants.|
|To prevent cataplexy and other REM-related symptoms||Dizziness, dry mouth, blurred vision, weight gain, constipation, trouble urinating, drowsiness, disturbance of heart rhythm. Should not be used with MAOIs or during immediate recovery from heart attack.|
|To prevent cataplexy and other REM-related symptoms||Nausea, dry mouth, headache, loss of appetite, nervousness, diarrhea or constipation, sweating, and sexual problems. Should not be used with MAOIs.|
|sodium oxybate* (Xyrem)||To prevent cataplexy, improve nighttime sleep, and reduce daytime sleepiness||Abdominal pain, chills, dizziness, abnormal dreams, drowsiness, stomach discomfort. Must be taken at bedtime and again during the middle of the night. Potential for abuse.|
|*Armodafinil, modafinil, and sodium oxybate are FDA-approved to treat narcolepsy symptoms. Other medications in this table are not, but physicians have found they often help people with narcolepsy and therefore prescribe them.|
Your doctor may ask you to visit a sleep laboratory for formal sleep testing. Fees depend on the level of testing required. Some people require a one-time consultation with a sleep specialist, which may run a few hundred dollars. Staying overnight in a sleep laboratory costs between $800 and $1,500. Home tests can cost from $300 to $600. Check with your insurance company in advance because reimbursement varies and may depend on your diagnosis.