Jaw Movement During Sleep

Abstract

Objective: We aim to improve our understanding of sleep physiology by describing the changes in mandibular position during sleep in normal subjects. Methods: We developed a novel method for mapping mandibular position simultaneously in three dimensions (anteroposterior, vertical and lateral) using magneto-resistive sensors strategically placed around 3 different moving joints on an external apparatus attached to the head and mandible. Spherical coordinates derived from these sensors provided information of jaw position in each of the three measurement planes. We assessed changes in jaw position in twelve healthy subjects (6 male, 6 female) aged (mean ± SD) 23 ± 7 years, Body Mass Index 22.5 ± 3.4 kg/m2, and with nasal resistance 3.24 ± 0.67 cmH2O/L/s by recording mandibular position simultaneously with overnight sleep polysomnography. Results: Jaw position was significantly influenced by sleep stage (p<0.001). The transition from wake to light sleep (stage one) was accompanied by significant jaw closure and jaw protrusion (p<0.05). As non-rapid-eye-movement (NREM) sleep deepened from stages 1 through slow wave sleep (SWS), vertical jaw opening (p<0.05) and posterior jaw movement progressively increased (p<0.05). REM sleep was associated with the greatest degree of jaw opening of all sleep stages (p<0.05). Lateral jaw position was not significantly different between sleep stages. Conclusion: This study describes, for the first time, an accurate method of measuring changes in mandibular position during sleep in all three dimensions. The observed changes during sleep in healthy subjects suggest a simultaneous modulation of upper airway muscular tone, which may be important in the understanding of upper airway occlusion in Obstructive Sleep Apnea.