study to get good epidemiological data on the occurrence of narcolepsy in the US. What we found is that narcolepsy is not uncommon. In a million people, we would expect about 550 narcoleptics and approximately 14 new cases of narcolepsy a year. What we found was that the first symptoms start most frequently between the ages of 10 and 20.
The second most frequent time of onset was the decade between ages 20 and 30, and the third most frequent was before the age of 10 and between the ages of 30 and 40. So narcolepsy is a disorder that frequently starts in young people, and physicians who look after adolescents should be especially aware of it. We found that it is slightly more common in men than in women, a ratio of 1.5 to 1. We have no explanation for this phenomenon at present. We also found that one doesn't have to have cataplexy in order to have narcolepsy. About 1/3 of narcolepsy patients don't develop cataplexy.
A sleep physician will take a careful history from the patient and his or her bed partner. A diagnosis is confirmed with an overnight sleep study and then a series of nap studies the following day, conducted every two hours. From this we will be able to see how quickly the patient falls asleep and whether they go quickly into rapid eye movement (REM) sleep. The propensity to go quickly into REM sleep is a marker for narcolepsy.
At present, we treat the symptoms; we don't treat the cause of the condition. We give medications that increase chemicals in the brain that are responsible for alertness.
There are a number of such medications available. Most narcoleptics are able to achieve 80% or more of their potential alertness with proper medication. We also have medications to treat cataplexy. Eventually we hope to have medications that act on the hypocretin system to treat the underlying cause, but that may be quite a while in the future.
--Michael H. Silber, MD, is a neurologist and sleep disorders specialist at the