Early rising or delayed bedtime: which is better for a short night's sleep?

Abstract

The present study compares the effects on sleep and the subsequent period of wakefulness of delaying bedtime of 2 h or advancing rising time by 2 h in subjects clearly differentiated by morningness or eveningness in their circadian rhythms. Twelve young healthy good sleepers, six morning types (MT) and six evening types (ET), were selected. The data obtained from the second 24 h (night and day) with delayed bedtime (DB) and advanced rising time (AR) were compared with those obtained in the reference condition (R) with normal sleep schedules. Sleep was recorded polygraphically and rectal temperature was continuously monitored during the nights and during the day following the second night of each condition. Subjective estimations of alertness, performance tasks and urinary steroids were analysed. Early rising appeared to be more disturbing than a late bedtime. The second shortened night showed fewer characteristics of recovery sleep in AR than in DB. The decrease in self rated alertness was a function both of the type of condition (DB or AR) and of the morning-evening typology of the subject. The largest decrease was observed in AR and in the ET subjects. AR also resulted in the most pronounced decrease in performance tasks and in an increase in urinary 17 ketosteroids without changes in the 17 hydroxy-corticosteroids. The effects on rectal temperature were limited to short periods after bedtime in DB and rising time in AR.

Chronotype: a review of the advances, limits and applicability of the main instruments used in the literature to assess human phenotype

“…The results indicated that there was a distinct difference between both chronotypes: evening types rated lower self-alertness upon waking compared with morning types. 49 Moreover, subjective and objective sleepiness has been shown to be greater in evening-type subjects than in morning-type subjects, especially in the morning. [50][51][52] It is important to note that, in all instruments, questions are predominantly subjective, relating sleep and activity times to a personal "feeling best" rhythm, 1 or asking subjects to assess hypothetical situations (e.g., "Considering only your own feeling best rhythm, at what time would you get up if you were entirely free to plan your day?").…”