PRESENTATION OF NARCOLEPSY AFTER 40

To advance understanding of the clinical spectra of narcolepsy, we ret rospectively reviewed the histories and clinical and polysomnographic features of 41 consecutive patients in whom this diagnosis was establi shed in our center over 3 years. A total of 51% presented after the ag e of 40 years. Among the older patients, three subpopulations were not ed: 1) narcolepsy/cataplexy with presentation delayed because of mild disease severity or misdiagnosis; 2) narcolepsy/cataplexy with diagnos is delayed until late-life expression of cataplexy; and 3) narcolepsy lacking cataplexy with later-life onset of excessive daytime sleepines s. Clinical, polysomnographic, and multiple sleep latency test assessm ents of rapid eye movement sleep dyscontrol and sleepiness were unrela ted to age. This analysis identified older patients lacking cataplexy as the least severely affected narcoleptic subgroup. Narcolepsy, a con tinuum of phenotypes and severities that masks its recognition, should be considered in the differential diagnosis of sleepiness or transien t loss of muscle tone in older patients.