If not treated, people with narcolepsy can fall asleep at any
time, such as when at work, while driving and while engaged in a
conversation. Narcolepsy is linked to a chemical in the brain
called hypocretin, which normally stimulates arousal and helps
regulate sleep. Most people with narcolepsy do not produce
hypocretin in the deep part of the brain called the
hypothalamus. As a result, the body's messages about when to
sleep and when to stay awake sometimes occur at the wrong times
and places. Narcolepsy is a lifelong condition that affects an
estimated one in 1,000 to 1,500 people. Although it occurs in
both men and women, it is slightly more common among men. The
condition can begin at any age, although its symptoms usually
appear between the ages of 10 and 20. Narcolepsy has been found
to be hereditary in some cases. The hallmark symptom of
narcolepsy is an excessive daytime sleepiness (EDS), in which a
person falls asleep at times when they want to be awake. EDS may
include daytime sleep attacks that occ