A significant increase in breathing amplitude precedes sleep bruxism

Objectives: Sleep Bruxism (SB) is a stereotyped movement disorder characterized by rhythmic masticatory muscle activity (RMMA) and tooth grinding (TG). Recent evidence suggests that SB is associated with sleep micro-arousals and that most RMMA episodes are preceded by physiological changes occurring in sequence, namely, a rise in autonomic sympathetic-cardiac activity followed by a rise in the frequency of electroencephalographic and suprahyoid muscle activity. In the present study we hypothesize that an increase in respiration also characterizes the onset of SB within the micro-arousal sequence.

Methods: Polygraphic sleep recordings of 20 SB subjects without any sleep related breathing disorders were analysed for changes in respiration (i.e. root mean square, area under the curve, peak, peak-to-peak and length) extracted from a nasal cannula signal. Variables were analysed and compared using ANOVA 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 (8-23%); the rise is higher at the onset of the suprahyoid activity (60-82%, 1 second before RMMA); and maximal during RMMA (108-206%) 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 (R2=0.26; p=0.02). The amplitude of respiratory changes was 11 times higher when micro-arousal was associated with RMMA in comparison to micro-arousal alone.

Conclusion: To our knowledge, this is the first report showing that RMMA-SB muscle activity is associated with a rise in respiration within micro-arousal.

This study was suppoted by a research grant from the CIHR