The effects of sleep bruxism on baroreflex control of the circulation in humans

 

Yoshiyuki Okada, Yoshi-ichiro Kamijo, Shizue Masuki, Kazunobu Okazaki, and Hiroshi Nose

Department of Sports Medical Sciences, Shinshu University Graduate School of Medicine, Matsumoto 390-8621, Japan

 

We have reported in awake human subjects that isometric biting evoked pressor responses; increased heart rate (HR), arterial blood pressure (BP) and muscle sympathetic nervous activity, which was accompanied by a reduction in baroreflex sensitivity (BRS, FASEB J, 21(6), A571, 2007). We examined whether these responses occurred also during sleep bruxism (SB) and, if so, whether the responses were altered when sleep deepened. We determined sleep stage by polysomnography while measuring HR by electrocardiogram and beat-by-beat BP with Finometer in 12 young subjects who slept over night for 6 hrs in a test room. We determined BRS from HR response to spontaneous change in systolic BP and also an index of sympathetic nervous activity (SNA) from low-frequency / high-frequency component of HR variability. We found that systolic BP, HR, and SNA decreased while BRS increased as sleep stage increased (P < 0.05). However, whenever SB for 3.5 min on average occurred, systolic BP, HR, and SNA increased and BRS decreased to their awake levels in any stages of sleep (all, P < 0.05). These responses were greater than those by isometric biting in awake subjects (P < 0.05). Thus, pressor responses were evoked by SB, accompanied by a reduction in BRS, and enhanced as sleep deepened.

 

Key words: Blood pressure, Circulation, Sleep