National Institutes of Health
National Heart, Lung, and Blood Institute
Facts About
Narcolepsy
What Is Narcolepsy?
Narcolepsy is a chronic sleep disorder with no known cause. 
The main characteristic of narcolepsy is excessive and
overwhelming daytime sleepiness, even after adequate
nighttime sleep.  A person with narcolepsy is likely to
become drowsy or to fall asleep, often at inappropriate
times and places.  Daytime sleep attacks may occur with or
without warning and may be irresistible.  These attacks can
occur repeatedly in a single day.  Drowsiness may persist
for prolonged periods of time.  In addition, nighttime sleep
may be fragmented with frequent wakenings.
Three other classic symptoms of narcolepsy, which may not
occur in all patients, are:
*     Cataplexy:  sudden episodes of loss of muscle
      function, ranging from slight weakness (such as
      limpness at the neck or knees, sagging facial muscles,
      or inability to speak clearly) to complete body 
      collapse.  Attacks may be triggered by sudden
      emotional reactions such as laughter, anger, or fear
      and may last from a few seconds to several minutes. 
      The person remains conscious throughout the episode.
*     Sleep paralysis:  temporary inability to talk or move
      when falling asleep or waking up.  It may last a few
      seconds to minutes.
*     Hypnagogic hallucinations:  vivid, often frightening,
      dream-like experiences that occur while dozing or
      falling asleep.
Daytime sleepiness, sleep paralysis, and hypnagogic
hallucinations can also occur in people who do not have
narcolepsy.
In most cases, the first symptom of narcolepsy to appear is
excessive and overwhelming daytime sleepiness.  The other
symptoms may begin alone or in combination months or years
after the onset of the daytime sleep attacks.  There are
wide variations in the development, severity, and order of
appearance of cataplexy, sleep paralysis, and hypnagogic
hallucinations in individuals.  Only about 20 to 25 percent
of people with narcolepsy experience all four symptoms.  The
excessive daytime sleepiness generally persists throughout
life, but sleep paralysis and hypnagogic hallucinations may
not.
The symptoms of narcolepsy, especially the excessive daytime
sleepiness and cataplexy, often become severe enough to
cause serious disruptions in a person's social, personal,
and professional lives and severely limit activities.
When Should You Suspect Narcolepsy?
You should be checked for narcolepsy if:
*     you often feel excessively and overwhelmingly sleepy
      during the day, even after having had a full night's
      sleep;
*     you fall asleep when you do not intend to, such as
      while having dinner, talking, driving, or working;
*     you collapse suddenly or your neck muscles feel too
      weak to hold up your head when you laugh or become
      angry, surprised, or shocked;
*     you find yourself briefly unable to talk or move while
      falling asleep or waking up.
How Common Is Narcolepsy?
Although it is estimated that narcolepsy afflicts as many as
200,000 Americans, fewer than 50,000 are diagnosed.  It is
as widespread as Parkinson's disease or multiple sclerosis
and more prevalent than cystic fibrosis, but it is less well
known.  Narcolepsy is often mistaken for depression,
epilepsy, or the side effects of medications.
Who Gets Narcolepsy?
Narcolepsy can occur in both men and women at any age,
although its symptoms are usually first noticed in teenagers
or young adults.  There is strong evidence that narcolepsy
may run in families; 8 to 12 percent of people with
narcolepsy have a close relative with the disease.
What Happens in Narcolepsy?
Normally, when an individual is awake, brain waves show a
regular rhythm.  When a person first falls asleep, the brain
waves become slower and less regular.  This sleep state is
called non-rapid eye movement (NREM) sleep.  After about an
hour and a half of NREM sleep, the brain waves begin to show
a more active pattern again, even though the person is in
deep sleep.  This sleep state, called rapid eye movement
(REM) sleep, is when dreaming occurs.
In narcolepsy, the order and length of NREM and REM sleep
periods are disturbed, with REM sleep occurring at sleep
onset instead of after a period of NREM sleep.  Thus,
narcolepsy is a disorder in which REM sleep appears at an
abnormal time.  Also, some of the aspects of REM sleep that
normally occur only during sleep--lack of muscle tone, sleep
paralysis, and vivid dreams--occur at other times in people
with narcolepsy.  For example, the lack of muscle tone can
occur during wakefulness in a cataplexy episode.  Sleep
paralysis and vivid dreams can occur while falling asleep or
waking up.
How Is Narcolepsy Diagnosed?
Diagnosis is relatively easy when all the symptoms of
narcolepsy are present.  But if the sleep attacks are
isolated and cataplexy is mild or absent, diagnosis is more
difficult.
Two tests that are commonly used in diagnosing narcolepsy
are the polysomnogram and the multiple sleep latency test. 
These tests are usually performed by a sleep specialist. 
The polysomnogram involves continuous recording of sleep
brain waves and a number of nerve and muscle functions
during nighttime sleep.  When tested, people with narcolepsy
fall asleep rapidly, enter REM sleep early, and may awaken
often during the night.  The polysomnogram also helps to
detect other possible sleep disorders that could cause
daytime sleepiness.
For the multiple sleep latency test, a person is given a
chance to sleep every 2 hours during normal wake times. 
Observations are made of the time taken to reach various
stages of sleep.  This test measures the degree of daytime
sleepiness and also detects how soon REM sleep begins. 
Again, people with narcolepsy fall asleep rapidly and enter 
REM sleep early.
How Is Narcolepsy Treated?
Although there is no cure for narcolepsy, treatment options
are available to help reduce the various symptoms. 
Treatment is individualized depending on the severity of the
symptoms, and it may take weeks or months for an optimal
regimen to be worked out.  Complete control of sleepiness
and cataplexy is rarely possible.  Treatment is primarily by
medications, but lifestyle changes are also important.  The
main treatment of excessive daytime sleepiness in narcolepsy
is with a group of drugs called central nervous system
stimulants.  For cataplexy and other REM-sleep symptoms,
antidepressant medications and other drugs that suppress REM
sleep are prescribed.  Caffeine and over-the-counter drugs
have not been shown to be effective and are not recommended.
In addition to drug therapy, an important part of treatment
is scheduling short naps (10 to 15 minutes) two to three
times per day to help control excessive daytime sleepiness
and help the person stay as alert as possible.  Daytime naps
are not a replacement for nighttime sleep.
Ongoing communication among the physician, the person with
narcolepsy, and family members about the response to
treatment is necessary to achieve and maintain the best
control.
What Is Being Done To Better Understand Narcolepsy?
Studies supported by the National Institutes of Health (NIH)
are trying to increase understanding of what causes
narcolepsy and improve physicians' ability to detect and
treat the disease.  Scientists are studying narcolepsy
patients and families, looking for clues to the causes,
course, and effective treatment of this sleep disorder. 
Recent discovery of families of dogs that are naturally
afflicted with narcolepsy has been of great help in these
studies.  Some of the specific questions being addressed in
NIH-supported studies are the nature of genetic and
environmental factors that might combine to cause narcolepsy
and the immunological, biochemical, physiological, and
neuromuscular disturbances associated with narcolepsy. 
Scientists are also working to better understand sleep
mechanisms and the physical and psychological effects of
sleep deprivation and to develop better ways of measuring
sleepiness and cataplexy.
How Can Individuals and Their Families and Friends Cope With
Narcolepsy?
Learning as much about narcolepsy as possible and finding a
support system can help patients and families deal with the
practical and emotional effects of the disease, possible
occupational limitations, and situations that might cause
injury.  A variety of educational and other materials are
available from sleep medicine or narcolepsy organizations.  
Support groups exist to help persons with narcolepsy and
their families.
Individuals with narcolepsy, their families, friends, and
potential employers should know that:
*     Narcolepsy is a life-long condition that requires
      continuous medication.
*     Although there is not a cure for narcolepsy at 
      present, several medications can help reduce its 
      symptoms.
*     People with narcolepsy can lead productive lives if
      they are provided with proper medical care.
*     If possible, individuals with narcolepsy should avoid
      jobs that require driving long distances or handling
      hazardous equipment or that require alertness for
      lengthy periods.
*     Parents, teachers, spouses, and employers should be
      aware of the symptoms of narcolepsy.  This will help
      them avoid the mistake of confusing the person's
      behavior with laziness, hostility, rejection, or lack
      of interest and motivation.  It will also help them
      provide essential support and cooperation.
*     Employers can promote better working opportunities for
      individuals with narcolepsy by permitting special work
      schedules and nap breaks.
For More Information
For additional information on sleep and sleep disorders,
contact the following offices of the National Heart, Lung,
and Blood Institute of the National Institutes of Health:
*     National Center on Sleep Disorders Research (NCSDR)  
The NCSDR supports research, scientist training,
dissemination of health information, and other activities on
sleep and sleep disorders.  The NCSDR also coordinates sleep
research activities with other Federal agencies and with
public and nonprofit organizations.
National Center on Sleep Disorders Research
Two Rockledge Centre 
Suite 7024
6701 Rockledge Drive, MSC 7920
Bethesda, MD  20892-7920
(301) 435-0199
(301) 480-3451 (fax)
*     National Heart, Lung, and Blood Institute Information
      Center
The Information Center acquires, analyzes, promotes,
maintains, and disseminates programmatic and educational
information related to sleep and sleep disorders.  Write for
a list of available publications or to order additional
copies of this fact sheet.
NHLBI Information Center
P.O. Box 30105
Bethesda, MD  20824-0105
(301) 592-8573
(301) 592-8563 (fax)
For more information about narcolepsy and patient support
groups, contact the Narcolepsy Network at P.O. Box 42460,
Cincinnati, OH 45242.
U.S. Department of Health and Human Services
Public Health Service
National Institutes of Health
National Heart, Lung, and Blood Institute
NIH Publication No. 96-3649
October 1996