title: The circadian and homeostatic modulation of sleep pressure during wakefulness differs between morning and evening chronotypes.
abstract: The purpose of this study was to evaluate homeostatic and circadian sleep process in 'larks' and 'owls' under daily life conditions. Core body temperature, subjective sleepiness and waking electroencephalogram (EEG) theta-alpha activity (6.25-9 Hz) were assessed in 18 healthy men (nine morning and nine evening chronotypes, 21.4 +/- 1.9 years) during a 36-h constant routine that followed a week of a normal 'working' sleep-wake schedule (bedtime: 23.30 h, wake time: 07.30 h). The phase of the circadian rhythm of temperature and sleepiness occurred respectively, 1.5 h (P = 0.01) and 2 h (P = 0.009) later in evening- than in morning-type subjects. Only morning-type subjects showed a bimodal rhythm of sleep-wake propensity. The buildup of subjective sleepiness, as quantified by linear regression, was slower in evening than in morning types (P = 0.04). The time course of EEG theta-alpha activity of both chronotypes could be closely fitted by an exponential curve. The time constant of evening types was longer than that of morning types (P = 0.03), indicating a slower increase in sleep pressure during extended wakefulness. These results suggest that both the circadian signal and the kinetics of sleep pressure buildup differ between the two chronotypes even under prior naturalistic conditions mimicking the usual working day.
authors: Clinique du sommeil, CHU de Bordeaux, Bordeaux, France. jack.taill@free.fr
authors: Jacques
authors: J
authors: Taillard
authors: Pierre
authors: P
authors: Philip
authors: Olivier
authors: O
authors: Coste
authors: Patricia
authors: P
authors: Sagaspe
authors: Bernard
authors: B
authors: Bioulac
mesh_terms: D000328:Adult; D001831:Body Temperature; D002940:Circadian Rhythm / Q000502:physiology*; D004569:Electroencephalography; D006706:Homeostasis / Q000502:physiology*; D006801:Humans; D008297:Male; D011312:Pressure; D011795:Surveys and Questionnaires; D014851:Wakefulness