title: The Circadian System Contributes to Apnea Lengthening across the Night in Obstructive Sleep Apnea.
abstract: OBJECTIVE
  To test the hypothesis that respiratory event duration exhibits an endogenous circadian rhythm.
  
  
  METHODS
  Within-subject and between-subjects.
  
  
  METHODS
  Inpatient intensive physiologic monitoring unit at the Brigham and Women's Hospital.
  
  
  METHODS
  Seven subjects with moderate/severe sleep apnea and four controls, age 48 (SD = 12) years, 7 males.
  
  
  METHODS
  Subjects completed a 5-day inpatient protocol in dim light. Polysomnography was recorded during an initial control 8-h night scheduled at the usual sleep time, then through 10 recurrent cycles of 2 h 40 min sleep and 2 h 40 min wake evenly distributed across all circadian phases, and finally during another 8-h control sleep period.
  
  
  RESULTS
  Event durations, desaturations, and apnea-hypopnea index for each sleep opportunity were assessed according to circadian phase (derived from salivary melatonin), time into sleep, and sleep stage. Average respiratory event durations in NREM sleep significantly lengthened across both control nights (21.9 to 28.2 sec and 23.7 to 30.2 sec, respectively). During the circadian protocol, event duration in NREM increased across the circadian phases that corresponded to the usual sleep period, accounting for > 50% of the increase across normal 8-h control nights. AHI and desaturations were also rhythmic: AHI was highest in the biological day while desaturations were greatest in the biological night.
  
  
  CONCLUSIONS
  The endogenous circadian system plays an important role in the prolongation of respiratory events across the night, and might provide a novel therapeutic target for modulating sleep apnea.
authors.affiliation: Oregon Institute of Occupational Health Sciences, Oregon Health & Science University, Portland, OR.|Department of Behavioral Neuroscience, Oregon Health & Science University, Portland, OR.|Division of Sleep and Circadian Disorders, Brigham and Women's Hospital, Boston, MA.|Division of Sleep Medicine, Harvard Medical School, Boston, MA.
authors.forename: Matthew P
authors.initials: MP
authors.lastname: Butler
authors.affiliation: Division of Sleep and Circadian Disorders, Brigham and Women's Hospital, Boston, MA.
authors.forename: Carolina
authors.initials: C
authors.lastname: Smales
authors.affiliation: Division of Sleep and Circadian Disorders, Brigham and Women's Hospital, Boston, MA.|Division of Sleep Medicine, Harvard Medical School, Boston, MA.|Department of Neurology, Changzheng Hospital, Second Military Medical University, Shanghai, China.
authors.forename: Huijuan
authors.initials: H
authors.lastname: Wu
authors.affiliation: Division of Sleep and Circadian Disorders, Brigham and Women's Hospital, Boston, MA.
authors.forename: Mohammad V
authors.initials: MV
authors.lastname: Hussain
authors.affiliation: Division of Sleep and Circadian Disorders, Brigham and Women's Hospital, Boston, MA.
authors.forename: Yusef A
authors.initials: YA
authors.lastname: Mohamed
authors.affiliation: Division of Sleep and Circadian Disorders, Brigham and Women's Hospital, Boston, MA.
authors.forename: Miki
authors.initials: M
authors.lastname: Morimoto
authors.affiliation: Oregon Institute of Occupational Health Sciences, Oregon Health & Science University, Portland, OR.|Department of Public Health and Preventive Medicine, Oregon Health & Science University, Portland, OR.|Division of Sleep and Circadian Disorders, Brigham and Women's Hospital, Boston, MA.|Division of Sleep Medicine, Harvard Medical School, Boston, MA.
authors.forename: Steven A
authors.initials: SA
authors.lastname: Shea
mesh_terms: D000328:Adult; D000368:Aged; D002940:Circadian Rhythm / Q000502:physiology*; D003624:Darkness; D005260:Female; D006801:Humans; D008027:Light; D008297:Male; D008550:Melatonin / Q000378:metabolism; D008875:Middle Aged; D008991:Monitoring, Physiologic; D010100:Oxygen / Q000378:metabolism*; D017286:Polysomnography; D012119:Respiration; D012463:Saliva / Q000378:metabolism; D012890:Sleep / Q000502:physiology; D020181:Sleep Apnea, Obstructive / Q000378:metabolism / Q000503:physiopathology*; D013997:Time Factors; D014851:Wakefulness / Q000502:physiology
chemical_list: D008550:Melatonin; D010100:Oxygen
keywords: apnea hypopnea index; arousal; clock; sleep disordered breathing; time of day