The Facts
Narcolepsy is a very rare sleep disorder, but it's fairly well known because
of its rather dramatic symptoms. Only about 3 people in 10,000 suffer from
this syndrome, which tends to be a lifelong phenomenon. The symptoms of narcolepsy
can be terrifying at first, and frustrating even after someone becomes used
to them, but they never produce any serious illness. People with narcolepsy
are usually healthy and normal in all other respects. They have exactly the
same natural life expectancy as those without it. No physical abnormality or
tissue damage has ever been linked to this condition, either as a cause or as
a consequence.
Men and women are equally likely to suffer from narcolepsy. It usually first
appears in the teenage years, but can come on at almost any age. Often the symptoms
appear one by one, but in people aged over 20 it's more likely that several
symptoms will appear at once. Symptoms may change over time in an individual,
but there's no general tendency for them to get worse or better with age.
Causes
It is not known what causes narcolepsy, but it certainly appears to be a
genetically inheritable condition. Not only has it been observed to run
in families, but also everyone who has been diagnosed with narcolepsy has one
of just a few particular tissue types.
Most symptoms of narcolepsy appear to occur when the brain suddenly enters
a state of REM (rapid eye movement) sleep in the daytime. A few symptoms
occur when the brain enters a REM-like condition without losing consciousness.
REM sleep itself is poorly understood. Most dreaming occurs during REM sleep,
but the significance of dreaming is itself a controversial and poorly understood
subject. Sleep always brings a reduction in muscle tone, blood pressure, and
pulse, but in REM sleep these changes are especially pronounced. Usually, in
a single night, people go from shallow (stage I) to very deep (stage IV) sleep
about five times. At the end of each of these cycles, the stage IV sleep is
replaced by a brief period of REM sleep.
In stage III and IV sleep, people often toss and turn and some even sleepwalk
or sleeptalk, but in REM sleep people tend to lie very still, and the only movement
is in the eyeballs, behind closed lids. During this period, a brainwave-measuring
device called an electroencephalogram (EEG) will show rapid low-voltage
activity throughout the brain. Sleep researchers can find these patterns in
almost everyone, but they do not yet know the significance of this. They also
have no idea how REM sleep or REM-like symptoms can appear suddenly in people
who are awake.
