title: A significant increase in breathing amplitude precedes sleep bruxism.
abstract: BACKGROUND
  Sleep bruxism (SB) is a stereotyped movement disorder that is characterized by rhythmic masticatory muscle activity (RMMA) and tooth grinding. Evidence has suggested that SB is associated with sleep arousals and that most RMMA episodes are preceded by physiologic changes occurring in sequence, namely, a rise in autonomic sympathetic-cardiac activity followed by a rise in the frequency of EEG and suprahyoid muscle activity. In the present study, we hypothesize that an increase in respiration also characterizes the onset of SB within the arousal sequence.
  
  
  METHODS
  Polygraphic sleep recordings of 20 SB subjects without any sleep-related breathing disorders were analyzed for changes in respiration (ie, root mean square, area under the curve, peak, peak-to-peak, and length) extracted from a nasal cannula signal. Variables were analyzed and compared using analysis of variance and correlation tests.
  
  
  RESULTS
  Measurements of respiration showed significant changes over time. Four seconds before RMMA muscle activity, the amplitude of respiration is already increased (8 to 23%); the rise is higher at the onset of the suprahyoid activity (60 to 82% 1 s before RMMA); the rise is maximal during RMMA (108 to 206%) followed by a rapid return to levels preceding RMMA. A positive and significant correlation was found between the frequencies of RMMA episodes and the amplitude of breath (R(2) = 0.26; p = 0.02). The amplitude of respiratory changes was 11 times higher when arousal was associated with RMMA in comparison to arousal alone.
  
  
  CONCLUSIONS
  To our knowledge, this is the first report showing that RMMA-SB muscle activity is associated with a rise in respiration within arousal.
authors.affiliation: Faculté de Médecine Dentaire et de Medicine, Université de Montréal, Montréal, QC, Canada.
authors.forename: Samar
authors.initials: S
authors.lastname: Khoury
authors.affiliation: Center for the Study of Brain Diseases, Centre Hospitalier de l' Université de Montréal Research Center-Notre Dame Hospital, Montréal, QC, Canada.
authors.forename: Guy A
authors.initials: GA
authors.lastname: Rouleau
authors.affiliation: Faculté de Médecine Dentaire et de Medicine, Université de Montréal, Montréal, QC, Canada.
authors.forename: Pierre H
authors.initials: PH
authors.lastname: Rompré
authors.affiliation: Department of Pneumology, Centre Hospitalier de l' Université de Montréal-Hotel Dieu Hospital, Montréal, QC, Canada.
authors.forename: Pierre
authors.initials: P
authors.lastname: Mayer
authors.affiliation: Centre d'Étude du Sommeil et des Rythmes Biologiques, Sacré-Coeur Hospital, Montréal, QC, Canada.
authors.forename: Jacques Y
authors.initials: JY
authors.lastname: Montplaisir
authors.affiliation: Faculté de Médecine Dentaire et de Medicine, Université de Montréal, Montréal, QC, Canada. Electronic address: gilles.lavigne@umontreal.ca.
authors.forename: Gilles J
authors.initials: GJ
authors.lastname: Lavigne
mesh_terms: D000328:Adult; D001143:Arousal / Q000502:physiology*; D015331:Cohort Studies; D005260:Female; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D008297:Male; D008410:Masticatory Muscles / Q000503:physiopathology*; D009119:Muscle Contraction / Q000502:physiology*; D017286:Polysomnography; D012119:Respiration; D012720:Severity of Illness Index; D020186:Sleep Bruxism / Q000503:physiopathology*