title: Multiple sleep bruxism data collected using a self-contained EMG detector/analyzer system in asymptomatic healthy subjects.
abstract: OBJECTIVE
  Small, self-contained electromyographic (EMG) detector/analyzer (D/A) devices have become available for the detection of jaw muscle activity events above threshold. These devices claim to be less intrusive to the subjects sleep so it is less prone to induce disturbed sleep. The objective of this study was to evaluate for night-to-night variability and examine for a systematic alteration on the first night in EMG levels.
  
  
  METHODS
  Ten asymptomatic healthy volunteers (mean age, 26.8 ± 3.78) were recorded for six sequential nights in their home environment using EMG D/A system. The device yields a nightly EMG level above threshold score on a 0-4 level. Because the data are categorical and nonparametric, the data of the ten subjects across six nights were submitted to a Friedman repeated measures ANOVA. The significant level was set as alpha equal to 0.05.
  
  
  RESULTS
  The median and mode values of the subjects were tabulated and analyzed and we did not find a significant difference in EMG D/A level across the six nights (p = 0.287, Kendall's coefficient of concordance = 0.124, Friedman two-way repeated measures ANOVA). The data did show clear and substantial night-to-night variability.
  
  
  CONCLUSIONS
  Substantial night-to-night variability in masseter EMG activity levels was clearly observed in our subjects. There was no evidence of a suppressed or elevated first-night effect-like variability on masseter muscle EMG level seen in these subjects using a small portable self-contained EMG detector/analyzer. These data suggest that recordings should be at least 5-6-nights duration to establish a reasonable measure of an individual's average nightly masseter EMG level.
authors.affiliation: Department of Oral Rehabilitation and Regenerative Medicine, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, 2-5-1 Shikata-cho, Kita-ward, Okayama, 700-8525, Japan.
authors.forename: Hajime
authors.initials: H
authors.lastname: Minakuchi
authors.forename: Chiyomi
authors.initials: C
authors.lastname: Sakaguchi
authors.forename: Emilio S
authors.initials: ES
authors.lastname: Hara
authors.forename: Kenji
authors.initials: K
authors.lastname: Maekawa
authors.forename: Yoshizo
authors.initials: Y
authors.lastname: Matsuka
authors.forename: Glenn T
authors.initials: GT
authors.lastname: Clark
authors.forename: Takuo
authors.initials: T
authors.lastname: Kuboki
mesh_terms: D000328:Adult; D004576:Electromyography / Q000295:instrumentation* / Q000706:statistics & numerical data; D004867:Equipment Design; D005260:Female; D006801:Humans; D008297:Male; D008406:Masseter Muscle / Q000503:physiopathology; D018670:Monitoring, Ambulatory / Q000295:instrumentation* / Q000706:statistics & numerical data; D017286:Polysomnography / Q000295:instrumentation* / Q000706:statistics & numerical data; D012016:Reference Values; D012815:Signal Processing, Computer-Assisted / Q000295:instrumentation*; D020186:Sleep Bruxism / Q000175:diagnosis* / Q000503:physiopathology