title: Association between the amount of alcohol intake and masseter muscle activity levels recorded during sleep in healthy young women.
abstract: OBJECTIVE
  The aim of this study was to determine if the amount of alcohol intake is associated with masseter muscle activity recorded during sleep.
  
  
  METHODS
  Sixty healthy young female subjects (average age, 23.0 +/- 1.9 years; range, 21 to 32 years) participated in the study. Subjects were asked to perform 6 consecutive nightly masseter electromyography (EMG) recordings by using a portable EMG recording system in their homes. Using a minimum threshold criterion, which was set at 20% of the maximum voluntary contraction level, the total duration of muscle activity per hour of sleep was calculated. EMG data obtained on the first night were excluded from the analysis to avoid the first-night effect, and the data of the remaining 5 nights were averaged. Further, the subjects were asked to fill out questionnaires regarding their daily alcohol intake during the recording period. The total ethanol content of the consumed alcohol was calculated using a standard conversion table for alcoholic beverages. The ethanol concentration of each type of alcohol was multiplied by the reported amount consumed on each day, and the average value for 5 days was calculated. The EMG data were considered as a dependent variable, while the alcohol data were considered as an independent variable. Linear regression analysis was used to assess a possible association between these variables.
  
  
  RESULTS
  The subjects who did not consume alcohol during the recording period (n = 28) or who provided incomplete data sets as a result of missing data (n = 9) were excluded. The data of the remaining 23 subjects (n = 23) were exclusively analyzed. The result of this analysis revealed that the total ethanol content of the consumed alcohol was significantly and positively related to the EMG duration variable (coefficient = 0.51, 95% confidence interval: 0.20 to 0.82, adjusted R2 = 0.33, P < .01).
  
  
  CONCLUSIONS
  The results suggest that the amount of alcohol intake is substantially associated with masseter muscle activity levels during sleep in young women.
authors.affiliation: Removable Prosthodontics, Graduate School, Tokyo Medical and Dental University, Tokyo, Japan.
authors.forename: Akimitsu
authors.initials: A
authors.lastname: Hojo
authors.forename: Tadasu
authors.initials: T
authors.lastname: Haketa
authors.forename: Kazuyoshi
authors.initials: K
authors.lastname: Baba
authors.forename: Yoshimasa
authors.initials: Y
authors.lastname: Igarashi
mesh_terms: D000328:Adult; D000428:Alcohol Drinking / Q000009:adverse effects*; D004576:Electromyography; D000431:Ethanol / Q000009:adverse effects; D005260:Female; D006801:Humans; D016014:Linear Models; D008406:Masseter Muscle / Q000187:drug effects* / Q000502:physiology; D012890:Sleep / Q000502:physiology; D020186:Sleep Bruxism / Q000139:chemically induced*
chemical_list: D000431:Ethanol