Associations Between Wake-Time and Sleep-Time Masticatory Muscle Activity and Clinical Correlates in Free-Living...

To investigate associations between wake-time and sleep-time masticatory muscle activity (MMA) in free-living adults with high levels of oral behaviours, and to examine associations with tooth wear, masticatory muscle pain, stress, and anxiety.

In this observational repeated-measures study, 30 adults (mean age 31.4 ± 11.2 years) reporting clenching or grinding behaviours were recruited following screening with the Oral Behaviours Checklist. MMA was recorded during 77 sessions (2-3 sessions per participant) under free-living conditions using a wearable electromyography device, capturing wake-time and sleep-time activity. Tooth wear was assessed from intraoral scans and photographs using a standardised index. Stress and anxiety were assessed using validated questionnaires, muscle tenderness by standardised palpation, and pain on awakening by self-report. Associations were analysed using correlation and multivariable models accounting for repeated measures and covariates.

Moderate associations were observed between sleep time and wake time MMA for episode frequency, duty time, and rhythmic masticatory muscle activity (RMMA%), and remained significant after adjustment for confounders. Tooth wear showed limited association with MMA after accounting for age and sex, whereas higher sleep-time RMMA was associated with muscle pain on awakening. MMA measures were not associated with perceived stress, anxiety, or oral behaviours.

Sleep-time and wake-time masticatory muscle activity showed partial within-individual coupling in free-living adults, suggesting that some quantitative features of MMA may be shared across behavioural states. Tooth wear and self-reported behaviours may not reflect current MMA, whereas pain on awakening may be more informative. Integrating objective MMA assessment across behavioural states may improve clinical evaluation of bruxism and related conditions.