The influence of age on the frequency of rhythmic masticatory muscle activity during sleep in general population differs from that in clinical research samples

BackgroundDuring sleep, limb and jaw muscle motor activity can be quantified by electromyography (EMG). The frequency of periodic limb activity during sleep increases with age in both the general and clinical research populations. The literature is controversial regarding stability, over age, of the frequency of rhythmic masticatory muscle activity (RMMA), which is one biomarker of sleep bruxism (SB). ObjectivesThe purpose of this retrospective sleep laboratory study was to assess if any change in RMMA frequency occurs over age in the general population (GP) and two clinical research (CR) samples. MethodsRMMA signals from polysomnography (PSG) recordings of 465 individuals, irrespective of SB awareness, were analysed. The sample comprised 164 individuals from the GP of Sao Paulo, and 301 individuals from Montreal and Osaka CR samples. Data were divided into two subgroups, younger (15-39) and older (40-80) participants. RMMA was classified as low frequency (<2 events/h) or high (>= 2 events/h). Pearson correlation (R) and B (slope) analyses were performed with power estimations. ResultsIn the GP sample, no significant change over age was noted in the RMMA index/year. In the CR samples, a significant reduction was observed in the RMMA index/year (-0.05) with age (R-2 = .042; p < .001; 3.5 to 1.5 RMMA/h from 20 to 60 years old). ConclusionsIn the GP, the RMMA index remained stable over age. In the CR samples, a significant, reduction was observed. Prospective studies with multiple home sleep recordings, in both general and clinical research populations, are needed before extrapolating from the present findings.