title: The relationship between mouth opening and sleep stage-related sleep disordered breathing.
abstract: OBJECTIVE
  To evaluate mouth opening during sleep and the possible correlations between mouth opening and specific patient characteristics.
  
  
  METHODS
  A total of 55 patients consecutively referred to assess snoring and suspected obstructive sleep apnea (OSA) were included. Sensors to record mouth opening were attached to each patient's face and synchronized with a standard polysomnogram. Mouth opening data were evaluated for each sleep stage as a percentage of maximum mouth opening. The patients were divided into 2 groups: patients with REM apnea hypopnea index (AHI) > NREM AHI (REM-dependent group = RD group), and patients with NREM AHI > REM AHI (NREM-dependent group = ND group).
  
  
  RESULTS
  A total of 42 patients (male 69.0%, mean age 51.4 ± 12.9 years) underwent successful data collection. The amount of mouth opening during stage 1 (18.8% ± 14.6%) was significantly smaller than stage 2 (23.7% ± 16.4%, p < 0.01) and REM (29.2% ± 20.3%, p < 0.01). Age, body mass index (BMI), Epworth Sleepiness Scale (ESS) score, and AHI exhibited no correlation with mouth opening. The RD and the ND groups exhibited similar age, BMI, ESS, and AHI variables, but the ND group opened their mouths significantly more than the RD group during total sleep time (28.3% ± 13.6% vs 17.8% ± 17.3%, p < 0.01), stage 1 (23.2% ± 13.5% vs 12.9% ± 14.3%, p < 0.01), stage 2 (28.1% ± 17.9% vs 17.9% ± 17.4%, p < 0.01), and REM (34.7% ± 19.2% vs 21.9% ± 19.8%, p < 0.05).
  
  
  CONCLUSIONS
  The ND patients opened their mouths wider than the RD patients during most sleep stages. The relationship between REM-dependent AHI and the amount of mouth opening may be a factor in the pathogenesis of OSA.
authors.affiliation: Department of Oral Health Sciences, University of British Columbia, Vancouver, BC, Canada.
authors.forename: Hiroko
authors.initials: H
authors.lastname: Tsuda
authors.forename: Alan A
authors.initials: AA
authors.lastname: Lowe
authors.forename: Hui
authors.initials: H
authors.lastname: Chen
authors.forename: John A
authors.initials: JA
authors.lastname: Fleetham
authors.forename: Najib T
authors.initials: NT
authors.lastname: Ayas
authors.forename: Fernanda R
authors.initials: FR
authors.lastname: Almeida
mesh_terms: D000367:Age Factors; D015992:Body Mass Index; D016009:Chi-Square Distribution; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009058:Mouth Breathing / Q000503:physiopathology*; D017286:Polysomnography; D012891:Sleep Apnea Syndromes / Q000503:physiopathology*; D012894:Sleep Stages / Q000502:physiology*; D012895:Sleep, REM / Q000502:physiology; D018709:Statistics, Nonparametric