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Volume 09 No. 11
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Accepted Papers

Scientific Investigations

Is there a First Night Effect on Sleep Bruxism? A Sleep Laboratory Study

Yoko Hasegawa, D.D.S., Ph.D.1,2,3; Gilles Lavigne, D.M.D., Ph.D.2,3; Pierre Rompré, M.Sc.2; Takafumi Kato, D.D.S., Ph.D.4; Masahiro Urade, D.D.S., Ph.D.1; Nelly Huynh, Ph.D.2,3
1Department of Dentistry and Oral Surgery, Hyogo College of Medicine, Nishinomiya City, Hyogo, Japan; 2Faculté de medicine dentaire, Université de Montréal, Montréal, Canada; 3Centre d'étude du Sommeil et des Rythmes Biologiques, Hôpital du Sacré-Coeur de Montréal, Montréal, Canada; 4Department of Oral Anatomy and Neurobiology, Graduate School of Dentistry, University of Osaka, Osaka, Japan

Study Objectives:

Sleep bruxism (SB) is reported to vary in frequency over time. The aim of this study was to assess the first night effect on SB.


A retrospective polysomnographic (PSG) analysis was performed of data from a sample of SB patients (12 females, 4 males; age range: 17-39 years) recorded in a sleep laboratory over 2 consecutive nights. Sleep parameters and jaw muscle activity variables (i.e., rhythmic masticatory muscle activity [RMMA]) for SB were quantified and compared between the 2 nights. Subjects were classified into groups according to severity of RMMA frequency, such as low frequency (2-4 episodes/h and/or < 25 bursts/h) and moderate-high frequency (≥ 4 episodes/h and ≥ 25 bursts/h).


Overall, no first night effects were found for most sleep variables. However, total sleep time, sleep efficiency, and stage transitions showed significant time and group interactions (repeated measures ANOVAs, p ≤ 0.05). The RMMA episode index did not differ between the 2 nights, whereas the second night showed significantly higher burst index, bruxism time index, and mean burst duration (repeated measure ANOVAs, p ≤ 0.05). Five patients of 8 in the low frequency group were classified into the moderate-high frequency group on the second night, whereas only one patient in the moderate-high frequency group moved to the low frequency group.


The results showed no overall first night effect on severity of RMMA frequency in young and healthy patients with SB. In clinical practice, one-night sleep recording may be sufficient for moderate-high frequency SB patients. However, low RMMA frequency in the first night could be confirmed by a second night based on the patient's medical and dental history.


Hasegawa Y; Lavigne G; Rompré P; Kato T; Urade M; Huynh N. Is there a first night effect on sleep bruxism? A sleep laboratory study. J Clin Sleep Med 2013;9(11):1139-1145.

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