Nocturnal REM latency and sleep disturbance in narcolepsy.

A retrospective study of 92 narcoleptics was undertaken to investigate the significance of prolonged nocturnal REM latencies observed in approximately one in every five narcoleptics undergoing single all-night clinical polysomnograms in our laboratory. Clinical and laboratory findings were examined as a function of REM latency. Our findings emphasize a high incidence of other sleep disorders, particularly sleep-related periodic leg movements, in narcoleptics. Furthermore, sleep disturbance secondary to other sleep disorders, especially during the period of NREM sleep preceding the first REM episode, accounts in large part for prolonged REM latencies observed in some narcoleptics. This study also provides one of the most extensive compilations of clinical and laboratory findings in a large population of narcoleptics.