The effect of sleep position on sleep bruxism in adults with obstructive sleep apnea

Background: Most of the respiratory events in adults with obstructive sleep apnea (OSA) occurs in supine position. It has been reported that the contraction of masseter muscles is dependent on the occurrence of arousals rather than on the occurrence of respiratory events. Objectives: This study had two aims: (1) to compare the rhythmic masticatory muscle activity (RMMA) index in supine position (RMMA_sup) and in non-supine positions (RMMA_nsup) in adults with OSA; and (2) to determine the associations between RMMA index in both supine position and non-supine positions on the one hand, and several demographic and polysomnographic variables on the other hand. Methods: One hundred OSA participants (36 females and 64 males; mean age = 50.3 years (SD = 10.5)) were selected randomly from among patients with a full-night polysomnographic recording. RMMA_sup index and RMMA_nsup index were compared using Mann–Whitney U-test. Multivariate linear regression analyses were used to predict RMMA index both in supine and non-supine positions based on several demographic and polysomnographic variables. Results: In patients with OSA, the RMMA_sup index was significantly higher than the RMMA_nsup index (p <.001). RMMA_sup index was significantly associated with the arousal index (p =.002) and arousal index in supine position (p <.001). RMMA_nsup index was only significantly associated with the arousal index in non-supine positions (p =.004). Conclusion: Within the limitations of this study, RMMAs occur more frequently in supine position than in non-supine positions in patients with OSA. In both sleep positions, RMMAs are associated with arousals.