PARASOMNIAS
Association Between Sleep Bruxism, Swallowing-Related Laryngeal Movement,
and Sleep Positions
Shouichi Miyawaki DDS, PhD1,2,3; Gilles J. Lavigne DMD, MSc, FRCD1,3,4; Pierre Mayer MD1,4; F. Guitard1,3; Jacques Y. Montplaisir MD, PhD, CRCP(c)1,3; Takafumi
Kato DDS, PhD1,3,4
1Facultés de médecine et de médecine dentaire, Université de Montréal, Québec, Canada; 2Department of Orthodontics, Okayama University Graduate School of Medicine and Dentistry, Okayama, Japan; 3Centre d’étude du sommeil, Hôpital du Sacré-Coeur de Montréal, Québec, Canada;
4Departments of Pneumology and Stomatology, Centre Hospitalier de l’Université de Montréal, Hôtel-Dieu, Québec, Canada
sleeping time in the supine and lateral decubitus positions, respectively. In
both groups, up to 96% of rhythmic masticatory muscle activity and swallowing were observed in the supine and lateral decubitus position. In sleep
bruxism patients, although sleeping time did not differ between the 2
sleeping body positions, 74% of rhythmic masticatory muscle activity and
swallowing events were scored in the supine position compared to 23% in
the lateral decubitus position.
Conclusions: During sleep, rhythmic masticatory muscle activity is often
associated with swallowing. In sleep bruxism patients, most of these oromotor events are observed in the supine position. The physiologic link
between rhythmic masticatory muscle activity and swallowing and the clinical relevance of sleep position in sleep bruxism management need to be
investigated.
Key Words: Sleep bruxism, rhythmic masticatory muscle activity, swallowing-related laryngeal movement, sleep position, tooth grinding noise
Citation: Miyawaki S, Lavigne GJ, Mayer P et al. Association between
sleep bruxism, swallowing-related laryngeal movement, and sleep positions. SLEEP 2003;26(4):461-465.
Study Objective: To describe the relationships of sleep bruxism to swallowing and sleep positions.
Design: Controlled descriptive study.
Setting: Polysomnography and audio-video recordings were done in a
hospital sleep laboratory.
Participants: Nine patients with sleep bruxism and 7 normal subjects
were matched for age and sex.
Interventions: n/a
Measurements and Results: During sleep, patients with sleep bruxism
showed a higher frequency of rhythmic masticatory muscle activity
episodes (6.8 ± 1.0 [SEM]/h) than did normals (0.5 ± 0.1/h, p<0.01). Swallowing-related laryngeal movements occurred more frequently in sleep of
patients with sleep bruxism (6.8 ± 0.8/h) than in normals (3.7 ± 0.3/h,
p<0.01). In both groups, during sleep, close to 60% of rhythmic masticatory muscle activity episodes were associated with swallowing. In sleep
bruxism patients, 68% of swallowing events occurred during rhythmic
masticatory muscle activity episodes, while only 10% of swallowing events
were associated with rhythmic masticatory muscle activity in normal subjects. Sleep bruxism patients and normals spent 95.5% and 87.3% of
INTRODUCTION
During the sleep of healthy humans, various orofacial activities occur,
such as swallowing, coughing, sleep talking, and RMMA.2,2b The role of
swallowing during sleep may be to lubricate the esophagus and to contribute to preventing pulmonary aspiration.9-11 Interestingly, most swallowing events have been observed in light non-rapid eye movement
(NREM) sleep—defined as sleep stages 1 and 2—and, occasionally, in
rapid eye movement (REM) sleep.12 Furthermore, it has been suggested
that spontaneous swallowing during sleep is associated with sleep
arousal activity.12-14 In healthy young adults, swallowing frequency per
hour of sleep is reported to be up to 10 times lower during sleep in comparison to the awake state.12,15,16 Interestingly, RMMA has also been
reported to occur predominantly in light NREM sleep (and occasionally
in REM) and to be associated with micro-arousals.5,8,17-19
Normal young adults spend approximately 60% of their total sleep
time in the lateral decubitus position, 25% in the supine, and still less
time in the prone position.20 In patients with obstructive sleep apnea syndrome (OSAS), apneic events are observed more frequently in the
supine position.21 However, an association between the presence of SB
episodes and sleep positions is not evident in middle-aged and older subjects with or without OSAS.22-25 The RMMA episodes in SB patients are
frequently concomitant with body movements or leg jerks.8,18,26,27 In the
absence of confounding factors (eg, OSAS, age), it is unknown whether
oromotor activities such as RMMA and swallowing bear different relations to various sleep positions.
The purpose of this study was to test the hypothesis that: 1) swallowing is an oropharyngeal activity associated with RMMA during sleep
and 2) the occurrence of RMMA and swallowing is influenced by sleep
position.
SLEEP BRUXISM (SB) IS AN INVOLUNTARY ACTIVITY OF JAW
MUSCLES ASSOCIATED WITH TOOTH GRINDING DURING
SLEEP.1-3 Approximately 8% of the adult population suffers from SB.
The condition can be associated with severe dental problems (eg, tooth
damage, masticatory muscle and temporomandibular-joint pain,
headache).1-3 The pathophysiology for SB has not been definitively
established (eg, neurochemistry, autonomic system, sleep arousal).1-3
The jaw-muscle activity related to SB is similar to rhythmic masticatory-muscle activity (RMMA), defined as 3 or more repetitive jaw-muscle
bursts, which is observed in nearly 60% of normal subjects during
sleep.4 In SB patients, RMMA episodes constitute approximately 90% of
SB episodes and are nearly 3 times more frequent, with a 40% higher
muscle burst amplitude, than in normal subjects.4-6 The high rate and frequency of EMG activity in SB patients may lead to the longer duration
of total electromyographic activity and to more frequent grinding noise
than in normal subjects.5-8
Disclosure Statement
This study was supported by the Canadian Institutes of Health Research and
Fonds de la recherché en santé du Québec.
Submitted for publication September 2002
Accepted for publication January 2003
Address correspondence to: Takafumi Kato, DDS, PhD, Matsumoto Dental University, Institute of Oral Science, 1780 Gobara, Hirooka, Shiojiri, Nagano,
Japan 399-0781, Tel: + 81 263 52 3100 (ext.5464 or 2231); Fax: + 81 263 51
2223 or + 81 263 53 3456; E-mail: [email protected]
SLEEP, Vol. 26, No. 4, 2003
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Sleep Bruxism, Swallowing and Sleep Position—Miyawaki et al
METHODS
mocouple, Protech, Woodinville, USA). To assess swallowing events,
laryngeal movement was recorded with a piezoelectric sensor (Opti-flex
sensors, Newlife Technologies, Midlothian, VA, USA). This sensor was
attached to the skin over the thyroid cartilage. All biosignal data were
recorded at a sampling frequency of 128 Hz using recording and analysis software (Harmonie, Stellate system, Montréal, Canada). Audiovideo recordings of the head and upper body were made for visual scoring of orofacial and laryngeal movements.2,2b,12,28,29
Prior to sleep, baseline values were recorded in the supine position for
the following measurements: voluntary tooth clenching and tapping, lateral and vertical head movements, coughing, and saliva swallowing.5 All
of these activities were repeated 3 times. Spontaneous swallowing
events were also recorded during wakefulness before the light was
turned off. The sleep recordings were carried out from around 22:30 to
06:30, or at the time subjects awoke.
Subjects
Nine SB patients (6 males and 3 females; age [mean ± SD]: 25.3 ± 7.7
years) were recruited based on the following: 1) a history of tooth-grinding, occurring more than 3 times per week for at least 6 months; 2) a
report of jaw-muscle fatigue or discomfort in the morning; 3) the presence of tooth wear; and 4) masseter muscle hypertrophy. They were then
invited to sleep-laboratory sessions. The first night was used for laboratory adaptation, and the second night was used to diagnose SB and to
rule out other sleep disorders (eg, apnea, periodic limb movements).
Sleep bruxism was diagnosed if patients met the following polysomnographic research criteria: more than 4 RMMA episodes per hour, more
than 25 RMMA bursts per hour, and a minimum of 2 or more episodes
with grinding noise during sleep.2b,4,5
Ten healthy subjects, without any of the aforementioned clinical findings, were selected as controls to be matched to the SB patients. However, 3 of them were excluded after sleep recording because they showed
either low sleep efficiency (less than 80%) or frequent RMMA episodes
(more than 4 episodes/h) in the absence of grinding noise or frequent
oromandibular myoclonus.28 Finally, data from 7 subjects (4 males and
3 females; age: 23.2 ± 1.7 years) were used for analyses. Note that all
normals selected had RMMA and that 4 of them had 1 RMMA episode
with grinding noise, but none met the above polygraphic criteria for SB.
None of the above subjects had any history or signs of sleep or medical disorders or pain, nor were they taking medication known to influence sleep or motor activity. All subjects were provided with an
informed consent according to the human research institutional review
board.
Scoring and Analysis
The sleep stages, micro-arousals (eg, abrupt shifts in EEG frequency
characterized by theta, alpha or fast frequencies lasting for 3 to 10 seconds) and awakenings (eg, EEG frequency shift for more than 10 seconds) were scored according to standard ASDA criteria with a modified
20-second scoring page.30,31,31b Sleep duration (minutes), sleep efficiency (%), frequencies of micro-arousals and awakenings (per hour), and
sleep-stage distribution (%) were calculated for each subject.
The SB episodes were scored as previously described: 1) RMMA
episode was detected by visual recognition on the monitor, and 2) an
episode was accepted if the EMG level was at least 10% of the awake
maximum voluntary contraction. Boxes were drawn on manually selected bursts, and episode types were identified using an automated program.4 A phasic (rhythmic) episode was scored if it corresponded to at
Data Recording
least 3 EMG bursts of 0.25 to 2.0 seconds duration. A tonic episode was
scored if a sustained EMG burst lasted more than 2.0 seconds, and a
Data of the second night were analyzed in the present study. Polymixed episode was scored when both phasic and tonic episodes were
graphic recordings included: electroencephalograms (EEGs) from C3A2
present within a 3-second interval. The phasic (rhythmic) and mixed
and O2A1; electrocardiogram (ECG); bilateral electrooculograms
types of SB episodes, regardless of tooth grinding, were selected as
(EOGs); and electromyograms (EMGs) from suprahyoid, masseter, temRMMA episodes.4,5 These episodes represented 97.6% and 97.0% of all
poralis, and anterior tibialis muscles. To assess respiratory function,
episodes in normal subjects and SB patients, respectively. The overall
nasal airflow was indirectly measured with a thermistor sensor (Therfrequency of RMMA episodes, percentage of
RMMA episodes in each sleep stage, and pera
b
c
d
e
f
g
h
centage of RMMA episodes that included a
swallowing event were also calculated for each
SH
subject. Furthermore, the duration of RMMA
C3A2
episodes with and without tooth-grinding noise
R-MA
and the total sum were calculated.
L-MA
Sleep swallowing events, defined as swallowing-related laryngeal movements in this
TH
study, were mainly scored according to signals
LM
from laryngeal-movement sensors12,15,32 in
addition to the following: suprahyoid EMG
activity, transient interruption of nasal airflow
i
j
(swallowing apnea), and visual observation of
SH
laryngeal upward movement on video.12,33,34
For each subject, the concordance between
C3A2
laryngeal movement and swallowing was
R-MA
ensured by asking the subject to voluntarily
L-MA
swallow their saliva in a supine position.12,32
During sleep, the swallowing related to larynTH
geal movement had a similar signal pattern to
LM
that of voluntary swallowing during wakefulness and could be differentiated from nonswalFigure 1—Upper panel: Sensor signals related to head and jaw movements and to swallowing-related laryngeal movement
lowing signals such as tooth clenching or tapduring wakefulness and sleep. Examples of the polygraphic signal patterns related to awake voluntary tooth clenching (a) and
tapping (b), lateral (c) and vertical (d) head movements, coughing (e), and two oral saliva bolus swallowing (f, g) and a sponping, lateral and vertical head movements, and
taneous swallowing (h) in the supine position. The laryngeal movement (LM) related to swallowing events (f-h) can be clearcoughing (Figure 1). The between-observer
ly differentiated from others (a-e). Lower panel: Swallowing events that occurred without (i) or with (j) RMMA during sleep
(SM&FG) scoring concordance for swallowing
are illustrated. Signal patterns related to swallowing events during sleep are very similar to those observed during wakefulness (f-h in the upper panel). SH: suprahyoid electromyogram (EMG), C3A2: electroencephalogram, left (L) and right (R) masevents was 95.0%. The frequency of overall
seter (MAS) EMG, TH: nasal airflow. Vertical bars: 100mV, Horizontal bar: 3 seconds.
swallowing events, percentage of swallowing
SLEEP, Vol. 26, No. 4, 2003
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Sleep Bruxism, Swallowing and Sleep Position—Miyawaki et al
events in each sleep stage, percentage of swallowing events occurring
during RMMA episodes, and the frequency of swallowing events during
RMMA episodes were calculated for each subject. If a swallowing event
occurred during an RMMA episode, the timing of the swallowing event,
(ie, whether it occurred in the initial third, middle third, or last third of
the RMMA episode) was assessed.
Sleep positions (eg, supine [on the back], lateral decubitus [on the
side], and prone [on the stomach]) were scored visually using audiovideo recordings.21,35,36 The sleep duration in each sleep position was
calculated. Major body movements, related to large trunk movement
with or without changing the sleep position, were scored using audiovideo recordings. The percentage of RMMA episodes and swallowing
events for each sleep position, and the percentage of RMMA episodes
and swallowing events that occurred with major body movement, were
calculated. None of the subjects recorded in the present study had more
than 10 periodic leg movements per hour of sleep.
sleep. In comparison to normals, SB patients had a higher percentage of
swallowing events (1.7 times) in stage 2 of NREM sleep (P<0.01) and,
conversely, a lower percentage (2.3 times less) during REM sleep
(P<0.05, Table 2B).
In both groups, approximately 60% of RMMA episodes were associated with swallowing events (Table 2C). Although the percentage of
swallowing events that occurred during an RMMA episode was significantly higher in SB patients (7 times) than in normal subjects (P<0.01),
patients had less swallowing in the absence of SB episodes (P<0.01).
When swallowing events occurred with RMMA episodes, more than
50% of swallowing events were found during the last third of RMMA
episodes for both normals and SB patients (Table 2C). The SB patients
showed more frequent swallowing during the last third of RMMA
episodes than in the initial third (P<0.001), while, in normals, only a
trend for such a temporal pattern was found (P= 0.038).
Normal subjects tended to sleep for a longer time in the lateral decubitus position than in the prone position (P= 0.018, Table 3). In the SB
patients, the time spent sleeping in the supine (P=0.015) and lateral
decubitus (P=0.012) positions were significantly longer than in the
prone position. No difference was found between supine and lateral
decubitus positions in either group. The percentage of time spent in each
position was not different between groups.
In both groups, up to 96% of both RMMA episodes and swallowing
events occurred in the supine and lateral decubitus positions (Table 3).
The occurrence of these oromotor activities did not differ between the
supine and lateral decubitus positions in normal subjects. In SB patients,
3 times more RMMA and swallowing were observed in the supine position (74%) than in the lateral decubitus position (P=0.015 for RMMA
and swallowing).
The percentage of RMMA episodes occurring with body movement
was significantly lower in the SB patients (26.7 ± 5.0%, P<0.01) than in
Statistical Analyses
Sleep variables (eg, sleep-stage distribution), oromotor variables (eg,
frequency and sleep-stage distribution of oromotor episodes, duration of
RMMA with or without grinding noise), and variables related to sleep
positions and major body movements were compared between groups
using the Mann-Whitney U test. For these comparisons, probability levels of P<0.05 were considered statistically significant. Multiple paired ttests were used compare the timing of the swallowing events in RMMA
episodes within a group. To compare the percentage of sleeping time,
RMMA episodes, and swallowing events between 3 sleep positions,
multiple Wilcoxon tests were made within a group. For multiple comparisons, the P value required for statistical significance was determined
as 0.016 using Bonferroni correction. Data are presented by mean ±
SEM, and the uncorrected P values are presented. These statistical tests
were made using statistical analysis software (Statview, SPSS, Chicago,
IL, USA).
Table 2—Oromotor variables in normal subjects and sleep bruxism
patients
RESULTS
The overall sleep structure was similar between groups with the
exception of the frequency of sleep micro-arousals, which was significantly higher in the SB patients (P<0.01) although it was within the normal range (Table 1).37-39
The RMMA episodes occurred predominantly in light sleep stages 1
and 2 of NREM sleep in SB patients (85.1%) and in normal subjects
(66.9%) (Table 2A). The frequency of RMMA episodes in SB patients
was 13 times higher than that of the normal group (P<0.01). However,
the distribution of RMMA episodes across sleep stages did not differ
between groups. The mean total duration of RMMA over a total sleep
period was significantly longer (9 times) in the SB patients than in normal subjects (P<0.01).
The frequency of overall swallowing events was also significantly
higher (1.8 times) in SB patients than in normal subjects (P<0.01). In
both groups, most events were observed in light sleep stages of NREM
A. RMMA episodes
Frequency of RMMA episodes/h
Distribution of RMMA by sleep stages
Stage 1
Stage 2
Stages 3&4
REM
Percentage of RMMA episodes
with grinding noise
Total duration of RMMA
over sleep (min)
Total duration of RMMA with
grinding noise over sleep (min)
B. Swallowing-related laryngeal movements
Frequency of swallowing/h
Distribution of swallowing by sleep stages (%)
Stage 1
Stage 2
Stages 3&4
REM
Table 1—Sleep variables in normal subjects and sleep bruxism
patients.
Sleep duration (min)
Sleep efficiency (%)
Micro-arousals/h
Awakenings/h
Sleep-stage distribution (%)
Stage 1
Stage 2
Stages 3&4
REM
Normal subjects (n=7)
SB patients (n=9)
436.6 (12.8)
95.4 (0.9)
5.0 (0.6)
3.5 (0.5)
423.5 (13.8)
93.8 (1.7)
13.0 (2.1)**
4.0 (0.9)
6.8 (0.9)
58.4 (3.0)
14.0 (2.3)
20.9 (1.2)
6.1 (1.7)
58.0 (2.6)
13.7 (2.6)
22.2 (1.9)
SB patients
(n=9)
0.5 (0.1)
6.8 (1.0) **
11.2 (7.6)
55.7 (17.2)
9.5 (7.0)
23.5 (11.9)
16.0 (3.9)
69.1 (2.8)
6.4 (1.3)
8.5 (2.5)
35.7 (14.7)
43.7 (9.0)
0.9 (0.2)
8.1 (1.1) **
0.2 (0.1)
4.4 (1.1) **
3.7 (0.3)
6.8 (0.8) **
36.4 (2.8)
38.0 (3.3)
3.8 (1.7)
21.8 (3.9)
21.0 (5.2)
64.8 (4.0) **
4.9 (1.7)
9.3 (2.7) *
C. Association between RMMA and swallowing
Percentage of RMMA episodes
that included swallowing
58.6 (7.9)
Percentage of swallowing events
that occurred during RMMA
10.3 (1.0)
Frequency of swallowing in
absence of RMMA/h
3.4 (0.7)
Timing of swallowing event within RMMA episodes
Percentage in the initial third
14.2 (9.9)
Percentage in the middle third
21.4 (7.9)
Percentage in the last third
64.2 (10.6)
56.9 (8.1)
68.0 (5.5) **
1.9 (0.7) **
14.6 (3.1)
31.2 (5.5)
54.2 (4.6) †
Data are presented as mean (SEM). SB, sleep bruxism; RMMA, rhythmic masticatory muscle activity; *: p<0.05; **: p<0.01; †: p<0.016 is used with Bonferroni correction, compared
with the initial third.
Data are presented as mean (SEM). SB, sleep bruxism; REM, rapid eye movement
**: p<0.01.
SLEEP, Vol. 26, No. 4, 2003
Normal subjects
(n=7)
463
Sleep Bruxism, Swallowing and Sleep Position—Miyawaki et al
normal subjects (67.5 ± 10.5%) (Table 3). A few swallowing events
occurred with major body movement only when they were associated
with RMMA episodes (12.7 ± 2.2 % of total swallowing events in SB
patients, 2.5 ± 1.0 % in normals, P<0.01).
NREM sleep leads to a relatively lower percentage of swallowing events
during REM sleep compared to normal subjects who exhibited swallowing similarly in REM sleep as previously reported.12
How can we explain the association between RMMA and swallowing
during sleep? First, both oromotor activities are secondary to sleep
arousal.11,12,17-19 However, we should be cautious when making this
interpretation since our normal subjects showed a lower rate of microarousal than has been found in previous studies of normals and since the
index in SB patients was within the upper limit of the normal range.4,3739 Secondly, our SB patients showed a similar range of swallowing rate
during sleep (a mean of 6.8 events/h) as reported in previous studies
using similar techniques (5.8 to 7.5/h).12,15 Thus, the sleep of our normal
subjects was characterized by the low incidence of RMMA, microarousal, and swallowing. Third, subsequent analysis showed that 70% of
variability in RMMA is explained by micro-arousals and swallowing
when data from both groups are pooled (stepwise multiple regression, R2
= 0.7; P<0.01). Obviously, to substantiate such findings, further investigation is needed using a larger sample population and a continuous data
sample from normals to patients with light to severe SB.
One of the surprising findings of this study is that the frequency of
swallowing in SB patients during the periods when RMMA was absent
was 44% lower than swallowing in normals. Thus it could be possible
that the frequency of swallowing events during sleep, either with or
without RMMA, is associated with other physiologic functions. During
wakefulness, there is evidence that an increase in bite force or the induction of voluntary chewing or speaking-related oral movements trigger a
concomitant rise in salivary flow and subsequent swallowing activity.9,16,41-43 Thus, in SB patients, since most swallowing events occur with
RMMA episodes, there may be no further need to increase salivary flow
to lubricate the oral cavity and the upper alimentary tract during sleep.9
This hypothesis needs to be supported by prospective studies assessing
whether a rise in the jaw-muscle activity of SB patients during sleep is
associated with a rise in oral saliva that in turn triggers swallowing.
Moreover, the influence of sleep-related changes in oral pH on sleep
arousal, RMMA, and swallowing is as yet unknown, although changes
in oral and esophagus acid concentration (eg, secondary to gastroesophageal reflux) have been reported to increase sleep arousal and swallowing during sleep.9,14,44
Regarding sleeping body position, SB patients were similar to apneic
patients who spent 50% to 58% of their sleeping time in the supine position.35,36 However, this was not significantly different compared to normal subjects. Although sleeping time in the supine position can be
increased due to the presence of leads and cables that restrict position
changes during polygraphic recording in the sleep laboratory,36 normal
subjects in this study spent a similar length of time in the supine (20%30%) and lateral decubitus (40%-60%) positions, as has also been
observed in another group of young adults.20 So far, the association
between SB and sleep position has not been clearly demonstrated. The
frequency of SB episodes in patients with OSAS was not significantly
higher in the supine position than in the lateral position,22-24 while in
geriatric subjects without OSAS, SB episodes were more frequently
observed in the supine position.25 In the present study, SB patients without respiratory problems showed close to 74% of RMMA and swallowing in the supine position, although the percentage of sleeping time spent
did not differ between the supine and lateral decubitus positions. This
suggests that sleep position may contribute to the higher probability of
oromotor events. Again, further investigation is necessary before it can
be concluded that the supine position causes more RMMA or swallowing. In addition, sleep position is reported to explain only 25% of the
variance between the frequency of jaw-muscle activity and sleep apnea
in patients with OSAS.22 In SB patients, only 26.7% of major body
movements were related to SB episodes, as reported previously.8 It
remains to be investigated whether sleep-position adjustment is clinically relevant in SB management, as it has been suggested in some OSAS
patients.21,35
In conclusion, our data suggest that swallowing during sleep is asso-
DISCUSSION
The present study confirmed that the duration of RMMA episodes
with grinding noise was longer in SB patients than in normals. The SB
patients also showed a higher frequency of swallowing events during
sleep than did normal subjects, and, in SB patients, approximately 70%
of swallowing events occurred during an RMMA episode. Moreover,
90% of RMMA episodes, as well as swallowing-related laryngeal
movements, were observed in the supine and lateral decubitus sleeping
positions. In SB patients, these oromotor activities occurred 3 times
more frequently in the supine position than in the lateral decubitus position.
In keeping with previous reports, we found a comparable mean duration of RMMA episodes.6,7,24,25 Some normal subjects have presented
tooth-grinding sound in the absence of awareness or history of tooth
grinding; following sleep laboratory recording, they showed a very low
number of RMMA episodes. Moreover, in moderate to severe SB
patients, the occurrence of RMMA episodes with grinding sounds is
known to be variable, up to 50% over time.40
When scoring SB to study the specificity of SB pathophysiology, it is
important to distinguish swallowing from other orofacial activities.2,2325,28,29 In the present study, suprahyoid EMG activity and a transient
interruption of the nasal airflow were used in parallel with visual observation of a laryngeal upward movement to score swallowing. Others
have used this technique during wakefulness.33,34 However, in SB
patients, due to high jaw-muscle activity during RMMA episodes, it is
difficult to score specific suprahyoid EMG activity and nasal airflow in
relation to swallowing. Therefore, in addition to polygraphic and audiovideo recording, we indirectly identified swallowing events using laryngeal movement with a noninvasive sensor, as has been reported in previous studies.12,15,32 Using this method, swallowing events during sleep
could be recognized with a high interobserver scoring agreement (Figure
1). However, this method should be recognized as an indirect assessment
of swallowing activity.
Since both RMMA and swallowing have been reported to occur in
light NREM sleep and to be associated with sleep arousals,5,12-14,17-19 we
hypothesized that swallowing is associated with RMMA during sleep.
Effectively, this study supports this hypothesis since close to 60% of
RMMA episodes, in both normal subjects and SB patients, included at
least 1 swallowing event. In this study, up to 85% of RMMA and swallowing were scored in light NREM sleep of normals and SB patients.
Thus, in SB patients, the higher number of RMMA episodes in light
Table 3—Rhythmic masticatory muscle activity and swallowing in
relation to sleep position.
Normal subjects
(n=7)
Duration of sleep position (% in time)
Supine position
35.7 (8.8)
Lateral decubitus position
51.6 (5.5)
Prone position
12.6 (6.2)
RMMA episodes (%)
Supine position
49.0 (14.4)
Lateral decubitus position
51.0 (14.4)
Prone position
0
Swallowing events (%)
Supine position
58.5 (7.7)
Lateral decubitus position
38.4 (6.9)
Prone position
3.2 (1.6)
SB patients
(n=9)
54.3 (10.3) †
41.2 (8.7) †
4.5 (2.5)
74.4 (7.8) †, §
23.1 (6.7)
2.5 (1.7)
74.3 (7.4) †, §
22.7 (6.1) †
3.0 (1.8)
Data are presented as mean (SEM). SB, sleep bruxism; RMMA, rhythmic masticatory muscle activity; †: p<0.016 is used with Bonferroni correction, compared with prone position;
§: p<0.016 is used with Bonferroni correction, compared with lateral decubitus position.
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81.
30. Rechtschaffen A, Kales A, editors. A manual of standardized terminology, techniques
and scoring system for sleep stages of human subjects. Los Angeles: UCLA Brain Information Service / Brain Research Institute; 1968.
31. Arousals scoring rules and examples: a preliminary report from sleep disorders atlas task
force of the American Sleep Disorders Association. Sleep 1992;15:173-84.
31b. Gosselin N, Michaud M, Carrier J, Lavigne G, Montplaisir J. Age difference in heart rate
changes associated with micro-arousals in humans. Clin Neurophysiol 2002;113:15171521.
32. Ertekin C, Pehlivan M, Aydogdu I, et al. An electrophysiological investigation of deglutition in man. Muscle Nerve 1995;18:1177-86.
33. Kijima M, Isono S, Nishino T. Coordination of swallowing and phases of respiration
during added respiratory loads in awake subjects. Am J Respir Crit Care Med
1999;159:1898-902.
34. Klahn MS, Perlman AL. Temporal and durational patterns associating respiration and
swallowing. Dysphagia 1999;14:131-8.
35. Yoshida K. Influence of sleep posture on response to oral appliance therapy for sleep
apnea syndrome. Sleep 2001;24:538-44.
36. Metersky ML, Castriotta RJ. The effect of polysomnography on sleep position: possible
implications on the diagnosis of positional obstructive sleep apnea. Respiration
1996;63:283-7.
37. Boselli M, Parrino L, Smerieri A, Terzano MG. Effect of age on EEG arousals in normal
sleep. Sleep 1998;21:351-7.
38. Mathur R, Douglas NJ. Frequency of EEG arousals from nocturnal sleep in normal subjects. Sleep 1995;18:330-3.
39. Guilleminault C, Pyares D, Abat F, Palombini L. Sleep and wakefulness in somnambulism. A spectral analysis study. J Psychosomatic Res 2001;51:411-6.
40. Lavigne GJ, Guitard F, Rompré PH, Montplaisir JY. Variability in sleep bruxism activity over time. J Sleep Res 2001;10:237-44.
41. Yeh CK, Johnson DA, Dodds MW, Sakai S, Rugh JD, Hatch JP. Association of salivary
flow rates with maximal bite force. J Dent Res 2000;79:1560-5
42. Losso EM, Singer JM, Nicolau J. Effect of gustatory stimulation on flow rate and protein content of human parotid saliva according to the side of preferential mastication.
Arch Oral Biol 1997;42:83-7.
43. Anderson DJ, Hector MP, Linden RW. The effects of unilateral and bilateral chewing,
empty clenching and simulated bruxism, on the masticatory-parotid salivary reflex in
man. Exp Physiol 1996;81:305-12.
44. Orr WC, Johnson LF. Responses to different levels of esophageal acidification during
waking and sleep. Dig Dis Sci 1998;43:241-5.
ciated with RMMA in both normals and SB patients. The putative role
of saliva as a lubricant protecting teeth from grinding damage and the
oral or esophageal mucosa from acid content needs to be further investigated in relation to swallowing and SB.3,9 The high incidence of
RMMA episodes in the supine position for SB patients may indicate the
importance of future research on the efficacy of controlling sleep position in the management of SB.
ACKNOWLEDGMENTS
The authors thank C. Manzini and P. Rompré for their support in this
research and A. Petersen for her contribution to the manuscript editing.
S. Miyawaki is a visiting research fellow from Okayama University,
Japan.
REFERENCES
1.
2.
2b.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.
24.
25.
26.
27.
28.
29.
Lavigne GJ, Manzini C: Bruxism. In Kryger MH, Roth T, Dement WC, eds. Principles
and practice of sleep medicine, 3rd ed. Philadelphia: WB Saunders; 2000:773-85.
Kato T, Thie NMR, Montplaisir JY, Lavigne GJ. Bruxism and orofacial movements during sleep. Dent Clin North Am 2001;45:657-84.
Kato T, Blanchet PJ, Montplaisir JY, Lavigne GJ. Sleep bruxism and other disorders
with orofacial activity during sleep. In Chokroverty S, Hening WA, Walters AS, eds.
Sleep and movement disorders. Butterworth-Heiniemann, Philadelphia;2003:273-285.
Lavigne GJ, Kato T, Kolta A, Sessle BJ. Neurobiological mechanisms involved in sleep
bruxism. Crit Rev Oral Biol Med 2003;14:30-46.
Lavigne GJ, Rompré PH, Poirier G, Huard H, Kato T, Montplaisir JY. Rhythmic masticatory muscle activity during sleep in humans. J Dent Res 2001;80:443-8.
Lavigne GJ, Rompré PH, Montplaisir J. Sleep bruxism: validity of clinical research
diagnostic criteria in a controlled polysomnographic study. J Dent Res 1996;75:546-52.
Sjöholm T, Lehtinen I, Helenius H. Masseter muscle activity in diagnosed sleep bruxists
compared with non-symptomatic controls. J Sleep Res 1995;4:48-55.
Kydd WL, Daly C. Duration of nocturnal tooth contacts during bruxing. J Prosthet Dent
1985;53:717-21.
Reding GR, Zepelin H, Robinson JE Jr, Zimmerman SO, Smith VH. Nocturnal teethgrinding: all-night psychophysiologic studies. J Dent Res 1968;47:786-97.
Thie NMR, Kato T, Bader G, Montplaisir JY, Lavigne GJ. The Significance of saliva during sleep and the relevance of oromotor movements. Sleep Med Rev 2002;6:213-27.
Orr WC. Gastrointestinal disorders. In Kryger MH, Roth T, Dement WC, eds. Principles
and practice of sleep medicine, 3rd ed. Philadelphia: WB Saunders; 2000:1113-22.
Orr WC. Gastrointestinal functioning during sleep: a new horizon in sleep medicine.
Sleep Med Rev 2001;5:91-101.
Lichter I, Muir RC. The pattern of swallowing during sleep. Electroencephogr Clin Neurophysiol 1975;38:427-32.
Castiglione F, Emde C, Armstrong D, et al. Nocturnal oesophageeal motor activity is
dependent on sleep stage. Gut 1993;34:1653-9.
Freidin N, Fisher MJ, Taylor W, et al. Sleep and nocturnal acid reflux in normal subjects
and patients with reflux oesophagitis. Gut 1991;32:1275-9.
Lear CSC, Flanagan JB Jr, Moorrees CFA. The frequency of deglutition in man. Arch
Oral Biol 1965;10:83-99.
Rudney JD, Ji Z, Larson CJ. The prediction of saliva swallowing frequency in humans
from estimates of salivary flow rate and the volume of saliva swallowed. Arch Oral Biol
1995;40:507-12.
Macaluso GM, Guerra P, Di Giovanni G, Boselli M, Parrino L, Terzano MG. Sleep bruxism is a disorder related to periodic arousals during sleep. J Dent Res 1998;77:565-73.
Kato T, Rompré P, Montplaisir JY, Sessle BJ, Lavigne GJ. Sleep bruxism: an oromotor
activity secondary to micro-arousal. J Dent Res 2001;80:1940-4.
Satoh T and Harada Y. Electrophysiological study on tooth-grinding during sleep. Electroencephalogr Clin Neurophysiol 1973;35:267-75.
Lorrain D, De Koninck J. Sleep position and sleep stages: evidence of their independence. Sleep 1998;21:335-40.
Cartwright RD, Diaz F, Lloyd S. The effects of sleep posture and sleep stage on apnea
frequency. Sleep 1991;14:351-3.
Phillips BA, Okeson J, Paesani D, Gilmore R. Effect of sleep position on sleep apnea
and parafunctional activity. Chest 1986;90:424-9.
Okeson JP, Phillips BA, Berry DT, Cook YR, Cabelka JF. Nocturnal bruxing events in
subjects with sleep-disordered breathing and control subjects. J Craniomandib Disord
1991;5:258-64.
Okeson JP, Phillips BA, Berry DT, Baldwin RM. Nocturnal bruxing events: a report of
normative data and cardiovascular response. J Oral Rehabil 1994;21:623-30.
Okeson JP, Phillips BA, Berry DTR, Cook YR, Cabelka J. Nocturnal bruxing events in
healthy geriatric subjects. J Oral Rehabil 1990;17:411-8.
Sjöholm TT, Polo OJ, Alihanka JM. Sleep movements in teeth grinders. J Craniomandib
Disord Fac Oral Pain 1992;6:184-91.
Bader G, Kampe T, Tagade T, Karlsson S, Blomqvist M. Descriptive physiological data
on a sleep bruxism population. Sleep 1997;20:982-90.
Kato T, Montplaisir JY, Blanchet PJ, Lund JP, Lavigne GJ. Idiopathic myoclonus in the
oromandibular region during sleep: a possible source of confusion in sleep bruxism
diagnosis. Mov Disord 1999;14:865-71.
Velly Miguel AM, Montplaisir J, Rompré PH, Lund JP, Lavigne GJ. Bruxism and other
orofacial movements during sleep. J Craniomandib Disord Facial Oral Pain 1992;6:71-
SLEEP, Vol. 26, No. 4, 2003
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