Narcolepsy is a disorder of excessive daytime sleepiness that usually develops during late adolescence or early adulthood and continues throughout the patient’s life. Although often considered a “rare” disease, type 1 narcolepsy with cataplexy (sudden loss of muscle tone while awake) is estimated to affect 1 in 3,000 Americans. Prevalence [Page 2184]rates vary around the world, from the lowest rate of 0.02% reported among the Israeli Jewish population to 0.18% reported among Japanese workers. The prevalence of narcolepsy type 2 (without cataplexy) is not known, but some authors estimate that it may be 3 times greater than the prevalence of narcolepsy type 1. Males and females are affected equally.

Patients with type I narcolepsy typically have both excessive daytime sleepiness and cataplexy, but patients who have ...