Premium
The circadian and homeostatic modulation of sleep pressure during wakefulness differs between morning and evening chronotypes
Author(s) -
Taillard Jacques,
Philip Pierre,
Coste Olivier,
Sagaspe Patricia,
Bioulac Bernard
Publication year - 2003
Publication title -
journal of sleep research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.297
H-Index - 117
eISSN - 1365-2869
pISSN - 0962-1105
DOI - 10.1046/j.0962-1105.2003.00369.x
Subject(s) - evening , chronotype , morning , circadian rhythm , wakefulness , psychology , endocrinology , medicine , electroencephalography , neuroscience , physics , astronomy
Summary 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.