Presentation of narcolepsy after 40.

To advance understanding of the clinical spectra of narcolepsy, we retrospectively reviewed the histories and clinical and polysomnographic features of 41 consecutive patients in whom this diagnosis was established in our center over 3 years. A total of 51% presented after the age of 40 years. Among the older patients, three subpopulations were noted: 1) narcolepsy/cataplexy with presentation delayed because of mild disease severity or misdiagnosis; 2) narcolepsy/cataplexy with diagnosis delayed until late-life expression of cataplexy; and 3) narcolepsy lacking cataplexy with later-life onset of excessive daytime sleepiness. Clinical, polysomnographic, and multiple sleep latency test assessments of rapid eye movement sleep dyscontrol and sleepiness were unrelated to age. This analysis identified older patients lacking cataplexy as the least severely affected narcoleptic subgroup. Narcolepsy, a continuum of phenotypes and severities that masks its recognition, should be considered in the differential diagnosis of sleepiness or transient loss of muscle tone in older patients.