Responsiveness of jaw motor activation to arousals during sleep in patients with obstructive sleep apnea syndrome.

Objectives: We aimed to characterize the association between jaw muscle contractions and respiratory events in patients with obstructive sleep apnea syndrome (OSAS) and to investigate the responsiveness of the contractions to respiratory events in comparison with that of leg muscles in terms of arousal types and sleep states. Methods: Polysomnographic (PSG) recordings were performed in 19 OSAS patients (F/M: 2/17; 53.1 +/- 13.7 years; AHI: 31.8 +/- 19.9/h) with no concomitant sleep bruxism or other sleep-related movement disorders. Muscle contractions of unilateral masseter (MAS) and anterior tibialis (AT) muscles were scored during sleep in association with graded arousals (microarousals and awakenings) related or unrelated to apnea-hypopnea events. Results: Arousals were scored for 68.2% and 52.3% of respiratory events during light NREM and REM sleep, respectively. Respiratory events with arousals were associated with longer event duration and/or larger transient oxygen desaturation than those without (ANOVAs: p < 0.05). Median response rates of MAS events to respiratory events were 32.1% and 18.9% during NREM and REM sleep. During two sleep states, MAS muscle was rarely activated after respiratory events without arousals, while its response rate increased significantly in association with the duration of arousals (Friedman tests: p < 0.001). A similar response pattern was found for AT muscle. Motor responsiveness of the two muscles to arousals after respiratory events did not differ from responsiveness to spontaneous arousals in two sleep stages. Conclusion: In patients with OSAS, the contractions of MAS and AT muscles after respiratory events can be nonspecific motor phenomena, dependent on the duration of arousals rather than the occurrence of respiratory events.