Comparison of EMG power during sleep from the submental and frontalis muscles.

Objective: Submentalis electromyography ( s EMG) and frontalis electromyography ( f EMG) muscle activities have been used to assist in the staging of sleep and detection of disruptions in sleep. This study was designed to assess the concordance between s EMG and f EMG power, by and across sleep stages.

Methods: Forty-three records with simultaneous acquisition of differential signals from the submental and frontalis muscles were evaluated. Sleep stages were assigned using the poly-somnography signals based on majority agreement of five technicians. The s EMG and f EMG signals were identically filtered and aligned prior to cross-correlation analysis.

Results: A strong concordance between s EMG and f EMG power was observed, with 95% of the records exhibiting at least moderate agreement. During rapid eye movement (REM) sleep, s EMG power was significantly less than f EMG power, but exhibited four times greater across-subject variability. f EMG power during wake and non-REM (NREM) sleep was greater than s EMG power, but with 50% less variability. Differences in wake and N1 mean power and between the other sleep stages were more distinct in the f EMG recordings. Relative changes in s EMG and f EMG power across wake, NREM, and REM stages were essentially identical with median by-subject cross correlations of 0.98 and interquartile ranges of 0.97 and 0.99, respectively.

Conclusion: The f EMG and s EMG power values were similar during wakefulness and sleep; however, the frontalis exhibits substantially less between-subject variability. This study established face validity for the use of f EMG in the detection of wake and stages of sleep, and for future applications toward assessment of quantitative REM sleep muscle activity in REM sleep behavior disorder.