IADR Abstract Archives
Rhythmic Masticatory Muscle Activity Across Sleep Cycles in Children
Objectives: Sleep bruxism (SB) is prevalent in children than in adults. However, pathophysiology of SB is largely unknown in children. This study aimed to investigate physiological association between sleep cycles and the occurrence of rhythmic masticatory muscle activity (RMMA) in children.
Methods: Overnight video-polysomnography was performed for the two study groups; 15 normal children (M:4; F:11, 10.6±3.2 years old, RMMA index: 5.6±1.3 times /hr) and 14 SB children (M:9; F:5, 10.4±2.5 years old, RMMA index: 1.3±0.5 times/hr). Sleep variables and RMMA episodes were scored according to the standard criteria. Sleep cycle was defined from the beginning of a continuous non-rapid eye movement (NREM) sleep period followed by a REM sleep period. Each sleep cycle was divided into four NREM segments and one REM segment. Power spectral analyses were done to quantify cortical electroencephalographic and electrocardiographic activities. RMMA index, micro-arousal index, slow wave activity (SWA), and sympatho-vagal balance were analyzed for each segment.
Results: Sleep architecture did not differ between two groups except for significantly higher micro-arousal index in SB children (7.8±2.4 times/hr) than normals (6.0±1.3 times/hr) (p<0.05). In both groups, approximately 70% of RMMA were found to occur in light NREM sleep. The number and duration of sleep cycles, and the amounts of SWA and sympatho-vagal balance did not differ across sleep cycles between the two groups. In both groups, RMMA most frequently occurred during the transition period from NREM sleep to REM sleep: the periods characterized by the increase of micro-arousals and sympathetic tone and by the decrease of SWA and parasympathetic tone.
Conclusions: RMMA occurred in association with normal sleep cycle dynamics regardless of the frequency of RMMA, although SB children exhibited higher number of RMMA than normal in children.
Methods: Overnight video-polysomnography was performed for the two study groups; 15 normal children (M:4; F:11, 10.6±3.2 years old, RMMA index: 5.6±1.3 times /hr) and 14 SB children (M:9; F:5, 10.4±2.5 years old, RMMA index: 1.3±0.5 times/hr). Sleep variables and RMMA episodes were scored according to the standard criteria. Sleep cycle was defined from the beginning of a continuous non-rapid eye movement (NREM) sleep period followed by a REM sleep period. Each sleep cycle was divided into four NREM segments and one REM segment. Power spectral analyses were done to quantify cortical electroencephalographic and electrocardiographic activities. RMMA index, micro-arousal index, slow wave activity (SWA), and sympatho-vagal balance were analyzed for each segment.
Results: Sleep architecture did not differ between two groups except for significantly higher micro-arousal index in SB children (7.8±2.4 times/hr) than normals (6.0±1.3 times/hr) (p<0.05). In both groups, approximately 70% of RMMA were found to occur in light NREM sleep. The number and duration of sleep cycles, and the amounts of SWA and sympatho-vagal balance did not differ across sleep cycles between the two groups. In both groups, RMMA most frequently occurred during the transition period from NREM sleep to REM sleep: the periods characterized by the increase of micro-arousals and sympathetic tone and by the decrease of SWA and parasympathetic tone.
Conclusions: RMMA occurred in association with normal sleep cycle dynamics regardless of the frequency of RMMA, although SB children exhibited higher number of RMMA than normal in children.