Night sleep does not predict day sleep in narcolepsy.

It has been suggested that the increased day sleep in narcolepsy-cataplexy is secondary to the known fragmentation and reduction of night sleep, there being no differences in 24 h sleep totals from normals. Twenty-two untreated patients underwent 24 h sleep wake recordings by ambulatory monitoring. Correlations were assessed by stepwise multiple regression between day sleep and night sleep measures. Almost no significant or near significant correlations emerged. It is concluded that day sleep in narcolepsy is based upon a different mechanism, perhaps a diurnal "subvigilance syndrome" of impaired arousal mechanisms.