Duration of EEG sleep stages in different types of disturbed night sleep.

The duration of each episode of any one electrophysiological sleep stage or any episode of intervening wakefulness was determined in three kinds of disturbed sleep, namely, in naturally impaired sleep of late middle-aged, normal people, in sleep after caffeine administration, and in sleep after hypnotic drug withdrawal. When compared with the sleep of young people, the sleep of late middle-aged subjects was characterized by an increase in longer episodes of intervening wakefulness plus drowsiness, and by a decrease in longer episodes of sleep stages 3 + 4 and REM. The sleep after caffeine, compared with the baseline sleep, contained an increased proportion of longer episodes of intervening wakefulness plus drowsiness but no significant change in the episode duration of any of the sleep stages. In the case of the drug withdrawal sleep, compared with the sleep on hypnotic drug, there was no change in the episode duration of intervening wakefulness plus drowsiness but there was a significant shortening of episode duration for sleep stages 2 and 3+4, with a similar trend for REM sleep episodes. Thus a sleep disturbance might be characterized by increased stability of wakefulness, by decreased stability of sleep or both. Different types of sleep disturbance might require different types of treatment.