Is there a first night effect on sleep bruxism? A sleep laboratory study.
OBJECTIVE
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.


METHODS
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).


RESULTS
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.


CONCLUSIONS
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.
Department of Dentistry and Oral Surgery, Hyogo College of Medicine, Nishinomiya City, Hyogo, Japan ; Faculté de medicine dentaire, Université de Montréal, Montréal, Canada ; Centre d'étude du Sommeil et des Rythmes Biologiques, Hôpital du Sacré-Coeur de Montréal, Montréal, Canada.
Yoko
Y
Hasegawa
Gilles
G
Lavigne
Pierre
P
Rompré
Takafumi
T
Kato
Masahiro
M
Urade
Nelly
N
Huynh
D000293:Adolescent; D000328:Adult; D000704:Analysis of Variance; D004562:Electrocardiography / Q000379:methods; D004569:Electroencephalography / Q000379:methods; D004576:Electromyography / Q000379:methods; D005260:Female; D006801:Humans; D008297:Male; D008410:Masticatory Muscles / Q000503:physiopathology; D009119:Muscle Contraction / Q000502:physiology; D010507:Periodicity; D017286:Polysomnography / Q000379:methods; D012189:Retrospective Studies; D012720:Severity of Illness Index; D012890:Sleep / Q000502:physiology*; D020186:Sleep Bruxism / Q000175:diagnosis / Q000503:physiopathology*; D012894:Sleep Stages / Q000502:physiology; D011795:Surveys and Questionnaires; D055815:Young Adult
Sleep bruxism; first night effect; polysomnography; rhythmic masticatory muscle activity; sleep laboratory