Sleep Profiles in Young Subjects With Rhythmic Masticatory Muscle Activity

Objectives: This study aimed to investigate objective and subjective characteristics of sleep in young subjects with frequency of rhythmic masticatory muscle activity (RMMA).
Methods: Video-polysomnographic recordings were done in 45 non-pain subjects with or without self-reported tooth grinding (age: 23.9 ± 2.2 years; F 23: M 20; BMI: 20.6 ± 1.6kg/m² ) for two consecutive nights in the sleep research laboratory of Osaka University Graduate School of Dentistry. Subjective sleep quality and anxiety level were assessed by the validated questionnaires. Unstimulated saliva was collected before and after sleep to measure salivary cortisol level. The data on the second night were used for the analysis. Subjects were divided into three groups according to the RMMA index (/h): high-RMMA (H) group (RMMA index ≥ 4; F 7 : M 8; n = 16), low-RMMA (L) group (2 ≤ RMMA index< 4; F 7: M 3; n = 10), and control (CTL) group (RMMA index < 2; F 9: M 8; n = 17). Variables were compared among the groups.
Results: Sleep macrostructure did not differ among the groups, except for the percentage of StageN1 being significantly higher in the H-group than the L-group. However, the latency of sleep onset, stageN2 and stageN3 significantly decreased from CTL- to H-group while sleep efficiency increased significantly. Micro-arousal index was significantly higher in the H-group than in the other groups. Subjective sleep quality, trait/state anxiety and salivary cortisol concentration in the evening and morning did not differ among the three groups.
Conclusions: Based on objective and subjective assessments in the sleep laboratory, sleep profiles of young subjects with frequent RMMA were normal except for a minor difference in some sleep variables.