[Intra-sleep awakenings in relation to habitual sleep length and modifications of the sleep-wake rhythms (author's transl)].

The number of episodes of intervening wakefulness, their duration and their sleep stage occurrence were analyzed in the sleep recordings of 19 young (19-23 years), good sleepers. There were 5 long sleepers (LS), 5 short sleepers (SS) and 9 regular sleepers (RS). The experimental protocol included 2 reference nights, a night sleep recovery (after 36 h of wakefulness) and a day sleep recovery (after 24 h). The night following the day sleep recovery was also recorded. The duration of waking episodes was very stable and was independent both of type of sleeper and of situation. The histogram of these durations seemed to follow an exponential law. The number of awakenings varied according to the individual, the habitual sleep length (SS had very few) and the situation (such as length of prior wakefulness or circadian factors).