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Sleep and wakefulness patterns in daytime naps of 50 patients with narcolepsy/cataplexy were compared with those of 50 controls. Each subject was monitored polygraphically during 2 one-hour nap periods. A sleep-onset REM period in either of the 2 daytime naps was observed to have a higher diagnostic sensitivity (78%) than an abnormally shortened sleep latency (68%). However, the specificities of a sleep-onset REM period (88%) or abnormally shortened sleep latency (90%) were quite similar. When the occurrence of either a sleep-onset REM period or a shortened sleep latency was evaluated in either of the two naps, the overall sensitivity was increased to 84% while the specificity was decreased only to 80%. The limitations of and indications for the use of testing for sleep and REM latencies in the diagnosis of narcolepsy in clinical practice are discussed.
Kales et al. (Wed,) studied this question.