title: Increased homeostatic response to behavioral sleep fragmentation in morning types compared to evening types.
abstract: OBJECTIVE
  To evaluate the influence of chronotype on sleep stages and quantitative sleep EEG when sleep pressure is increased and sleep schedule remains constant.
  
  
  METHODS
  A 5-day session comprising an adaptation night, a baseline night, two nights of sleep fragmentation, and a recovery night.
  
  
  METHODS
  Chronobiology laboratory.
  
  
  METHODS
  Twenty-four healthy subjects aged 19-34 years: 12 morning types and 12 evening types selected by questionnaire. Each group included 6 men and 6 women with a habitual sleep duration of 7 to 9 hours.
  
  
  METHODS
  Two nights of behavioral sleep fragmentation induced by forced 5-min awakenings every half-hour.
  
  
  RESULTS
  Each night of polysomnography recording lasted 8 hours and was based on each subject's preferred sleep schedule. On both nights of sleep fragmentation, stage 1 sleep increased, while both total sleep time and minutes of slow wave sleep decreased. No difference was observed in sleep architecture between morning types and evening types during sleep fragmentation nights or during recovery night. Spectral analysis of all-night NREM sleep EEG showed that during the recovery night, morning types had a larger fronto-central increase in low frequency activities and a larger centro-parietal decrease in 14-15 Hz activity than evening types. The largest group difference was for slow wave activity in the fronto-central area during the first part of the sleep episode.
  
  
  CONCLUSIONS
  These results add further support to a postulated difference in homeostatic sleep regulation between morning types and evening types, with morning types showing indications of a higher homeostatic response to sleep disruption.
authors.affiliation: Chronobiology Laboratory, Sacré-Coeur Hospital of Montréal, Québec, Canada.
authors.forename: Valérie
authors.initials: V
authors.lastname: Mongrain
authors.forename: Marie
authors.initials: M
authors.lastname: Dumont
mesh_terms: D000328:Adult; D002940:Circadian Rhythm; D004569:Electroencephalography; D005260:Female; D006706:Homeostasis / Q000502:physiology*; D006801:Humans; D008297:Male; D012892:Sleep Deprivation / Q000175:diagnosis* / Q000503:physiopathology*; D012894:Sleep Stages; D011795:Surveys and Questionnaires