Prevalence of temporomandibular disorders in fibromyalgia and
failed back syndrome patients: A blinded prospective
Ramesh Balasubramaniam, BDSc,aReny de Leeuw, DDS, PhD,bHua Zhu, MS,c
Robert B. Nickerson, MD,dJeffrey P. Okeson, DMD,eand Charles R. Carlson, PhD,f
UNIVERSITY OF KENTUCKY
Objectives. The objective of this study was to determine the prevalence of temporomandibular disorders (TMD) and
evaluate psychosocial domains in patients with fibromyalgia (FM) compared with patients with failed back syndrome
Study design. The study included 51 (32 FM and 19 FBS) adult patients who were administered orofacial pain and
psychological questionnaires before a clinical examination. Presence of TMD was diagnosed according to the
Research Diagnostic Criteria for TMD.
Results. Fifty-three percent of the FM patients reported having face pain compared with 11% of the FBS patients. Of
those FM patients who reported face pain, 71% fulfilled the criteria for a diagnosable TMD. FM patients had
significantly higher subscale scores for somatization, obsessive-compulsive, medication used for sleep, and fatigue
compared with FBS patients. Eighty-seven percent of the FM patients reported a stressful event and 42.3% had
symptoms indicating posttraumatic stress disorder.
Conclusion. The high prevalence of TMD and psychosocial dysfunction among FM patients suggests wide-reaching
dysregulation of autonomic and hypothalamic-pituitary-adrenal axis functions. (Oral Surg Oral Med Oral Pathol Oral
Radiol Endod 2007;104:204-16)
Fibromyalgia (FM) is defined by the American College
of Rheumatology (ACR) as a disorder characterized by
widespread pain and tenderness in at least 11 of 18
musculoskeletal sites for at least 3 months.1 Although
the ACR criteria are the standard criteria currently used
to study FM, it is believed that FM is not a musculo-
skeletal disorder per se; rather, it represents one end of
a spectrum of disorders that encompasses conditions
known as chronic widespread pain characterized by
widespread tenderness, pain severity, and distress.2-6
Given that the pain in FM is widespread and can
involve various parts of the body, it would be reason-
able to suggest that FM may overlap with temporoman-
dibular disorder (TMD), which is “a collective term
embracing a number of clinical problems that involve
the masticatory musculature, the temporomandibular
joint and associated structures.”7, p116 Numerous stud-
ies in the past have linked FM and TMD.8-13 These
studies have affirmed the frequency with which TM
symptoms are found among FM patients.
In a large sample of FM patients, 94% reported TMD
symptoms including pain and difficulty chewing and
mouth opening, which followed preexisting FM pain of
long duration.14 Studies including clinical examination
revealed that 68% to 97% of FM patients have signs
and symptoms of TMD.9,15,16 FM patients more com-
monly report TMD symptoms than vice versa.9 One
study reported that 75% of FM patients met the criteria
for TMD, whereas only 18% of TMD patients fulfilled
the FM criteria. Debate persists whether FM and TMD
should be considered distinct clinical entities or not.
FM has been considered far more debilitating with
respect to number of pain sites, somatic symptoms, and
level of pain intensity than TMD.17 In addition, FM
patients report more functional disability, work diffi-
culty, and overall health dissatisfaction.9 On the con-
trary, one study found that select clinical features, in-
cluding muscle palpation and mouth opening did not
differ between FM patients and those with masticatory
myofascial pain syndrome.18 Another study found that
aFormer Resident, Orofacial Pain, Orofacial Pain Center, University
bAssociate Professor, Orofacial Pain Center, University of Kentucky.
cPhD candidate, Department of Statistics, University of Kentucky.
dAssociate Professor, Department of Physical Medicine and Rehabil-
itation, School of Medicine, University of Kentucky.
eProfessor and Director of Orofacial Pain Center, University of
fProfessor, Orofacial Pain Center and Department of Psychology,
University of Kentucky.
Received for publication Oct 9, 2006; returned for revision Dec 22,
2006; accepted for publication Jan 5, 2007.
1079-2104/$ - see front matter
© 2007 Mosby, Inc. All rights reserved.
the type, intensity, description, and quality of pain were
similar in both TMD and FM patients.15 Thus, ambi-
guity exists with regard to the subjective as well as
objective features common in FM and TMD.
Several general health problems have been reported
to be equally frequent in FM and TMD patients. FM
and TMD share common symptoms such as muscle
pain, generalized pain sensitivity, sleep and concentra-
tion difficulties, bowel complaints, and headaches.19
Depression and anxiety are also common in FM as well
as in TMD patients.16,20 Thus, it has been suggested
that TMD may be considered a stress-related disorder
similar to FM and chronic fatigue syndrome. Stress-
related disorders are characterized by common somatic
and psychologic complaints such as fatigue, sleep dis-
turbances, anxiety, and depression.19,21
The above studies imply a relationship between
TMD and FM. However, the relationship is unclear as
many of the studies were retrospective or observational,
not blinded, not controlled, questionnaire based, and
most often had small sample sizes. Similarly, some of
the studies did not use the ACR classification1 for FM
and many studies did not define TMD or use the Re-
search Diagnostic Criteria (RDC) for TMD classifica-
tion,22 which are the currently accepted classifications
for these disorders.
The aim of the present study was to determine the
presence of TMD in FM patients compared with failed
back syndrome (FBS) patients. The FBS patients
served as a chronic pain control group. It was hypoth-
esized that FM patients would exhibit greater signs and
symptoms of TMD when compared with FBS patients.
It was also hypothesized that both FM and FBS patients
would exhibit significant psychosocial distress.
MATERIAL AND METHODS
This was a prospective study that involved recruiting
patients visiting the Physical Medicine and Rehabilita-
tion Clinic and patients visiting a FM workshop orga-
nized by the Center for the Advancement of Women’s
Health at the University of Kentucky between March
2005 and April 2006. The research was approved by the
Institutional Review Board for the Protection of Human
Patients. The study sample included 32 FM and 19 FBS
patients. The FM patients included in the study had
received a diagnosis by a single physical medicine and
rehabilitation specialist or rheumatologist, based on the
criteria for the classification of FM as established by the
ACR.1 The diagnosis of FBS was based on persistent or
recurrent, chronic lower back pain after at least one
failed surgical procedure of the lumbosacral spine.23-25
All interested patients were required to sign an in-
formed consent and were compensated $20 for their
Patients 18 years of age or older who presented with
a primary diagnosis of FM or FBS for at least 6 months
were eligible to participate in the study. Patients with
other chronic pains unrelated to the primary diagnosis,
uncontrolled metabolic diseases, neurological disor-
ders, uncontrolled vascular diseases, neoplasia, and
those currently undergoing psychiatric treatment were
excluded from the study.
Before the examination, all patients completed an
orofacial pain questionnaire and a battery of psycho-
logical assessments. The orofacial pain questionnaire
included questions about the patient’s sociodemograph-
ics, orofacial complaints, medical history, and pres-
ence of face and headache pain. Patients with current
face pain were required to provide details on its loca-
tion, onset, severity, quality,26 and aggravating and
ameliorating factors. Presence of mouth pain, head-
ache, and temporomandibular joint (TMJ) sounds and
dysfunction were also solicited. Disability or intention
to seek disability was also established.
Symptom Check List-90 —Revised (SCL-90-R),27 the
Pittsburgh Sleep Quality Index (PSQI),28 the Multidi-
mensional Pain Inventory (MPI),29 the Post-traumatic
Stress Disorder Checklist—Civilian Version (PCL-C),30
and Multidimensional Fatigue Symptoms Inventory—
short form (MFSI-SF).31
The SCL-90-R27 was used to assess current psy-
chological symptom status of the patients on 9 dimen-
sions. These dimensions include somatization, obses-
sive-compulsive behavior, interpersonal sensitivity,
depression, anxiety, hostility, phobic anxiety, paranoid
ideation, and psychoticism. It consists of a 90-item
multidimensional self-report inventory that is scored on
a 5-point scale of distress (0-4). A subscale score of 63
or above was deemed clinically significant. Test-retest
reliabilities range from r ? 0.78 to 0.90 for nonpatient
samples, and internal consistencies range from 0.77 to
The MPI29 was used to determine pain severity, as
well as to provide a pain profile classification of each
subject. It included 3 sections containing 61 questions.
The MPI pain profile classification is based on pain
level, social and physical activities, affective distress,
social support, and feelings of life control. Test-retest
reliabilities of the individual scale scores range from
r ? 0.68 to 0.86, and internal consistencies range from
0.73 to 0.90.29 Patients were classified into 3 prototypic
profiles, namely dysfunctional, interpersonally dis-
tressed, and adaptive copers. Other classification cate-
Volume 104, Number 2Balasubramaniam et al. 205
gories included hybrid, anomalous, and unanalyzable
profiles. The hybrid profile represents a combination of
prototypic profiles. Random responding, reading or re-
sponding difficulties, or faking bad or good responses
contributed to allocation of the anomalous profile.
When data were missing and statistical analyses of the
scores were not possible, the unanalyzable profile was
The PSQI28 was used to gather information regard-
ing the amount of hours the subject sleeps each night,
the amount of hours in bed each night, how often the
subject is awakened and why, as well as how difficult it
is for the subject to return to sleep upon awakening. A
PSQI total score of higher than 5 categorized subjects
as poor sleepers. The PSQI has exhibited test-retest
stability (full scale r ? 0.85), good overall internal
consistency (? ? 0.83), and provides a valid and reli-
able assessment of overall sleep quality and distur-
The PCL-C instrument was used to assess the pres-
ence of PTSD symptomatology. Before completing the
PCL-C, the patient was asked to identify any significant
traumatic stressors that she or he may have experienced
from 15 itemized statements The itemized statements
listed included military combat, violent attack, being
kidnapped, taken hostage, terrorist attack, torture, in-
carceration, natural or man-made disaster, severe auto
accident, being diagnosed with a life-threatening ill-
ness, sudden injury/serious accident, observed someone
hurt or killed, learning that her or his child has a
life-threatening illness, and an others category. Subse-
quently, the subject was asked to identify the most
significant stressor, indicate the date of occurrence, and
appraise how much the most significant stressor has
bothered her or him in the past month on the 17-item
PCL-C. These questions are graded from 1 (not at all)
to 5 (extremely) to indicate the impact of the most
significant traumatic stressor. Based on the subject’s
answers a likely diagnosis of PTSD as defined by the
DSM-IV33 may be ascertained. A cut-off score of 41 or
higher on the 17-item measure was deemed as PTSD
positive and a score of less than 41 was deemed PTSD
negative. The PCL-C has exhibited sensitivity of 0.85,
specificity of 0.90, positive predictive power of 74%,
negative predictive power of 95%, test-retest stability
(r ? 0.96), good overall internal consistency (? ?
0.92), and provides a valid and reliable assessment of
the presence of PTSD symptoms.30,34
The MFSI-SF identifies 5 facets of fatigue: (1) global
experience of fatigue; (2) somatic symptoms of fatigue;
(3) cognitive symptoms of fatigue; (4) affective symp-
toms of fatigue; and (5) behavioral symptoms of fa-
tigue.31 Each facet is calculated from the mean of 6
subscores of fatigue-related symptoms. The shortened
version (MFSI-SF), which consists of 30 statements,
was used for this study. Patients were asked to rate each
statement according to how true it has been for them
over the previous 7 days along a 5-point scale (0 ? not
at all; 4 ? extremely). There are no formal reliability
and internal consistency data for this assessment. How-
ever, de Leeuw et al.35 reported high overall internal
consistency for each of the subscales (0.88 ? alpha ?
0.96) using a TMD patient population and age and sex
The orofacial pain examination involved a thorough
clinical assessment by a dentist who was blinded to the
clinical diagnosis of the patients. The dentist was un-
aware with regard to whether he examined a FBS or
FM subject. The clinical examination was carried out
using a modified version of the examination protocol
that has been used at the University of Kentucky,
Orofacial Pain Center, for many years. The dentist was
trained at the Orofacial Pain Center and had performed
numerous similar clinical examinations. Based on the
clinical data and according to the RDC for TMD, a list
of prioritized diagnoses was made.22 These diagnoses
were verified by 2 other dentists trained at the Univer-
sity of Kentucky, Orofacial Pain Center. If there was a
disagreement between the 2 dentists as to the RDC
diagnoses for TMDs, a discussion was held among the
3 dentists until consensus was reached.
The analyses of the data involved comparing the FM
and FBS patients. Difference in age was tested using
the Student t test. Gender, education, marital status, and
smoking were tested using Fisher’s exact test, and
employment and disability were tested using the chi-
Comparison of the presence of orofacial pain be-
tween FM and FBS patients involved statistical analy-
ses using SAS 9.1 (SAS Institute Inc., Cary, NC),
namely the 2 sample t tests comparing mean scores
between the 2 groups, or chi-square/Fisher’s Exact tests
comparing the outcome percentages between the 2
groups. For the binary outcomes, odds ratio and 95%
confidence interval (CI) of the odds ratio were calcu-
Comparison of SCL-90-R symptom dimensions,
MPI subscales, and MFSI-SF and PSQI scores between
FM and FBS patients were tested using the 2 sample
t tests. Differences between FM and FBS patients in
MPI profile classification was tested using chi-square
test or Fisher’s exact test. Pearson product-moment
correlation was performed to determine the association
relationships between sleep disturbances and fatigue-
Balasubramaniam et al.
related symptoms between FM and FBS patients. Sig-
nificance level for all comparisons was set at P ? .05.
Differences between FM and FBS patients with regard
to presence of stressful life events and PTSD symptoms
were tested using Fisher’s exact test. Given the FM
study population did not include any males, statistical
analyses were repeated for FM and FBS groups with
females only to account for possible gender differences.
Sample size, sociodemographic characteristics,
prevalence, severity, and duration of TMD
The total sample was composed of 51 adult patients
(male ? 6; female ? 45). The FM group was composed
of 32 patients (male ? 0; female ? 32) with a mean age
of 52.2 ? 7.8 years. The FM group (P ? .002) differed
with respect to gender from the FBS group, which was
composed of 19 patients (male ? 6; female ? 13) with
a mean age of 50.0 ? 9.1 years. The 2 groups also
differed with respect to their education level (P ? .03),
where a greater number of FM (40.5%) patients had
college degrees in comparison with FBS (21%) pa-
tients. Tobacco use was significantly more prevalent
among the FBS (42%) compared with FM (3%) pa-
tients (P ? .0001). There were no significant differ-
ences between the 2 groups in regard to age (P ? .36),
marital status (P ? .60), employment (P ? .55), and
disability (P ? .48).
Fifty-three percent of the FM patients reported face
pain compared with 11% of the FBS group (P ? .002;
odds ratio ? 9.63, 95% CI ? 1.90-48.74). The FM
patients also reported a greater prevalence of headache
(78%) compared with the FBS patients (63%), but this
difference was not statistically significant (P ? .25).
Almost the same percentage of FBS patients (42%) and
FM patients (41%) reported mouth pain.
Of the FM patients who reported face pain, 71%
fulfilled the clinical RDC for TMD criteria. Of those
FM patients who did not report face pain, 47% fulfilled
the clinical RDC for TMD criteria. However, within the
FM group, the patients who reported face pain were not
significantly more likely to meet clinical RDC for TMD
criteria compared with the patients who did not report
face pain (P ? .17, odds ratio ? 2.74, 95% CI ?
0.64-11.75). Also, within the FBS group, the patients
who reported face pain (50%) were not significantly
more likely to meet the clinical RDC for TMD criteria
compared with the patients who did not report face pain
(12%) (P ? .30, odds ratio ? 7.5, 95% CI ? 0.32-
The various RDC for TMD diagnostic subcategories
were allocated for both FM and FBS patients. No
significant difference was found for any of the diagnos-
tic subcategories between the 2 groups (P ? .05; see
Table I). Fourteen of 19 FM patients received a muscle
diagnosis that included 6 myofascial pain and 8 myo-
fascial pain with limited opening. Two of the 3 FBS
patients who met the RDC criteria for TMD received a
muscle diagnosis and these 2 patients were diagnosed
with myofascial pain with limited opening. Four of 19
FM patients were diagnosed with a disk displacement
with reduction and this included any participant having
internal derangements in either or both joints. Arthral-
gia was diagnosed in 3, TMJ osteoarthritis in 5, and
TMJ osteoarthrosis in 7 of 19 FM patients, respectively.
Pain severity was measured based on a 0 to 10 visual
analogue scale and reported as 5.2 ? 2.1 and 3.5 ? 0.7
for the FM and FBS patients, respectively. Pain dura-
tion was calculated to be the time in months from when
the pain began through to the examination. Pain dura-
tion reported by patients was 50.3 ? 117.2 months and
53.5 ? 72.8 months for the FM and FBS patients,
respectively. No significant differences were found for
mean pain severity and mean pain duration between
FM and FBS patients by 2 sample t tests (P ? .29 and
Analyses of SCL-90-R data revealed numerically
higher scores on all subscales for FM as compared with
FBS patients, although these differences were not sta-
tistically significant for most scales. The FM patients
had statistically significantly higher scores for somati-
Table I. Comparison of TMD diagnoses between FM
(n ? 19) and FBS (n ? 3) patients (for patients who
met clinical RDC for TMD)*
TMD diagnosis FM FBSP†
Myofascial pain with
Disk displacement with
Disk displacement without
reduction, with limited
Disk displacement without
Osteoarthritis of the
Osteoarthrosis of the
711.00 1.2 (0.09-15.3)
*TMD, temporomandibular disorder; FM, fibromyalgia; FBS, failed
back syndrome; RDC, Research Diagnostic Criteria; NA, not avail-
able due to zero frequencies.
†Fisher’s exact test.
Volume 104, Number 2Balasubramaniam et al. 207
zation and obsessive-compulsive subscales compared
with the FBS patients. The FM patients had clinically
relevant subscale scores for somatization, obsessive-
compulsive, and depression, whereas the FBS patients
had a clinically relevant subscale score for somatization
(see Table II).
The FM patients had numerically higher scores on
pain severity, interference, affective distress, punishing
responses, household chores, outdoor work, and activ-
ities away from home scales and had lower scores on
life control, support, soliciting responses, distracting
responses, social activities, and general activities level
scales than the FBS patients. However, these differ-
ences were not statistically significant (P ? .05; see
Table III). When possible, patients were classified in 1
of the 3 main MPI profiles. Twenty-five percent of the
FM patients were classified as dysfunctional, 31% were
classified as interpersonally distressed, and 28% were
classified as adaptive copers. No significant differences
(P ? .05) were found between the FM patients and the
FBS patients with regard to the MPI main profile clas-
sification (see Table IV).
Both FM and FBS patients had elevated PSQI total
scores suggesting poor sleep but there was no signifi-
cant difference between the 2 groups. The mean score
for use of sleep medication was significantly different
between the FM and FBS patients (P ? .002), whereby
the FM patients had a higher score for sleep medication
use than the FBS patients. None of the other PSQI
scales showed significant differences between the FM
and FBS groups (see Table V).
There were significant differences between the FM
and FBS groups in the percentage of patients reporting
a stressful life event (P ? .04, odds ratio ? 5.2, 95%
CI ? 1.28-21.18). Eighty-seven percent of FM patients
Table II. Comparison of SCL-90-R symptom dimen-
sions between FM (n ? 31) and FBS (n ? 19) patients*
dimensionsGroup Mean SD P†
Interpersonal sensitivity .052
*SCL-90-R, Symptom Check List-90-Revised; FM, fibromyalgia;
FBS, failed back syndrome.
†Two-sample t test.
‡Statistically significant difference.
Table III. Comparison of MPI categories between FM
and FBS patients*
MPI scaleGroupnMean SDP†
Pain severity FM
Affective distress .059
Activities away from home .63
Social activities .32
General activity level .30
*MPI, Multidimensional Pain Inventory; FM, fibromyalgia; FBS,
failed back syndrome.
†Two-sample t test.
Table IV. Comparison of MPI profile classification
between FM (n ? 32) and FBS (n ? 19) patients*
MPI classes FM, n (%)FBS, n (%)P
.61 0.72 (0.21-2.5)
9 (28)7 (37).52 0.67 (0.20-2.3)
*MPI, Multidimensional Pain Inventory; FM, fibromyalgia; FBS,
failed back syndrome.
‡Fisher’s exact test.
Balasubramaniam et al.
reported a stressful life event compared with 56% of
FBS patients. Of the FM patients who reported a stress-
ful life event, 42.3% were considered PTSD positive
compared with 30% of the FBS patients. However,
there was no statistical evidence that FM patients were
more likely to have PTSD-positive symptoms than FBS
patients (P ? .71, odds ratio ? 1.71, 95% CI ?
FM patients had significantly higher general fatigue
(P ? .0001), emotional fatigue (P ? .008), physical
fatigue (P ? .0001), and mental fatigue (P ? .0001)
than FBS patients. The FBS patients had a higher vigor
score than the FM patients but this difference was not
statistically significant (see Table VI).
Among FM patients, the PSQI total score, subjective
sleep quality, sleep latency, sleep duration, and sleep
efficiency were correlated with one or more fatigue-
related symptoms (P ? .05; see Table VII). Among the
FBS patients, the PSQI total score, sleep latency, sleep
duration, sleep efficiency, sleep disturbances, and daytime
sleep dysfunction were correlated with one or more fa-
tigue-related symptoms (P ? .05; see Table VIII).
By excluding males from the analyses, the SCL-90R
results revealed that the FM patients had a significantly
higher mean somatization, obsessive-compulsive, inter-
personal sensitivity, and anxiety scores compared with
FBS patients (P ? .002, .001, .004, and .03, respec-
tively). FM patients also had significantly higher mean
pain severity, affective distress, punishing responses,
and outdoor work scores, but significantly lower mean
life control score compared with FBS patients (P ? .02,
.03, .04, .001, and .005, respectively). Correlations be-
tween PSQI scores and fatigue-related symptoms in the
FBS group excluding males maintained a positive cor-
relation between sleep duration and physical fatigue
score (r ? 0.63, P ? .03). Similarly, sleep disturbances
were positively correlated with general fatigue and
remained negatively correlated with vigor scores (r ?
0.58 and –0.73, P ? .04 and .005, respectively). In
addition, daytime sleep dysfunction remained posi-
tively correlated with the mental fatigue score (r ?
0.64, P ? .02), but did no longer show a significant
correlation with regard to general and physical fatigue.
Excluding the males did not have an impact on any of
the other statistics.
This study investigated the prevalence of symptoms
and signs of TMD in FM patients compared with an-
other sample of patients with chronic pain, namely
FBS. Fifty-three percent of the FM patients compared
with 11% of the FBS patients reported face pain indi-
cating that FM patients were 9.6 times more likely to
report face pain than the FBS patients. The greater
prevalence of face pain among FM patients compared
with FBS patients seems logical as FM represents one
end of a spectrum of chronic widespread pain condi-
tions.2-6 Given that the pain in FM is widespread and
can involve various parts of the body, it also seems
reasonable that FM may encompass TMD.7 Other stud-
ies have reported facial pain prevalence between 68%
and 97% in FM patients.8,15,16,17
Of the FM patients who reported face pain, 71% met
the clinical RDC criteria for TMD. The prevalence of
Table V. Comparison of PSQI scores between FM
(n ? 32) and FBS (n ? 19) patients*
PSQI scoreGroupMean SDP†
PSQI total scoreFM
Subjective sleep quality.77
Sleep efficiency .20
Use of sleep medication .002‡
Daytime sleep dysfunction.06
*PSQI, Pittsburgh Sleep Quality Index; FM, fibromyalgia; FBS,
failed back syndrome.
†Two-sample t test.
‡Statistically significant difference.
Table VI. Comparison of fatigue-related symptoms
(MFSI-SF) between FM (n ? 32) and FBS (n ? 19)
*MFSI-SF, Multidimensional Fatigue Symptoms Inventory—Short
Form; FM, fibromyalgia; FBS, failed back syndrome.
†Two-sample t test.
‡Statistically significant difference.
Volume 104, Number 2 Balasubramaniam et al. 209
TMD among FM patients in the current study is con-
sistent with a study by Plesh et al.9 that reported that
75% of FM patients met the RDC criteria for TMD.
Interestingly, 47% of FM patients who did not report
face pain also had the relevant signs that resulted in
them meeting the clinical RDC criteria for TMD. Pre-
vious studies have reported incongruence between re-
ported TMD symptoms and the clinical finding of TMD
signs. Patients may not report nontroublesome symp-
toms, whereas the clinician may find signs that are
clinically significant.36,37 Therefore, prevalence values
of TMD studies may overstate the clinical significance
relative to the patient complaints and thus mild and/or
transient symptoms and signs may inadvertently be
misinterpreted and lead to overtreatment.7 Essentially,
if FM patients did not report pain, allocation of a TMD
Table VII. Correlations between PSQI scores and fatigue-related symptoms (MFSI-SF) among FM patients (n ?
PSQI total score .50
Subjective sleep quality
Use of sleep medication
Daytime sleep dysfunction
*PSQI, Pittsburgh Sleep Quality Index; MFSI-SF, Multidimensional Fatigue Symptoms Inventory—Short Form; FM, fibromyalgia.
‡Statistically significant difference.
Table VIII. Correlations between PSQI scores and fatigue-related symptoms (MFSI-SF) among FBS patients
(n ? 19)*
PSQI total score.45
Subjective sleep quality
Use of sleep medication
Daytime sleep dysfunction
*PSQI, Pittsburgh Sleep Quality Index; MFSI-SF, Multidimensional Fatigue Symptoms Inventory—Short Form; FBS, failed back syndrome.
‡Statistically significant difference.
Balasubramaniam et al.
diagnosis based on clinical findings would not be ap-
propriate. Alternatively, failure to report face pain
among FM patients who had TMD signs may be be-
cause these patients assumed or had been previously
informed that their face pain was an extension of the
FM pain, rather than a separate entity.
FM patients who met the clinical criteria for RDC
muscle diagnoses included 32% who had myofascial
pain and 42% who had myofascial pain with limited
opening. Therefore, masticatory muscle pain was diag-
nosable in 74% of the FM patients. This prevalence of
masticatory muscle pain among FM patients was lower
than what has been previously reported in other stud-
ies.8,9,16,17 This may be because the examiner in this
study was blinded as to primary diagnosis (FM or FBS)
of the recruited patients, therefore diminishing possible
selection bias. In addition, many of the previous studies
did not use the RDC for TMD criteria and rather relied
on patient-reported symptoms alone8,17 or carried out
clinical examination without established diagnostic cri-
Disk displacement with reduction was diagnosed
among 21% of FM patients. It should be noted that this
diagnosis included painless clicking of the TMJ that
may be coincidental and not clinically relevant to FM.
It has been reported that disk displacement with reduc-
tion, which includes clicking of the TMJ, may occur in
up to a third of asymptomatic patients and therefore
should not be used as an exclusive sign of the presence
of TMD requiring treatment.38
Arthralgia was diagnosed in 16% of the FM patients
and TMJ osteoarthritis was diagnosed in 26% of FM
patients. Therefore, 42% of TMJs of FM patients were
painful on palpation and during function. A previous
study reported that 80% of FM patients had pain or
did not use the RDC criteria for TMD and therefore
comparisons with our results were not possible.15 Osteo-
arthrosis of the TMJ was diagnosed in 37% of FM pa-
tients. This may be an underestimation as radiographic
that “exhibit erosion of normal cortical delineation, scle-
rosis of parts or all of the condyle and articular eminence,
flattening of joint surfaces and osteophyte formation that
did not exhibit crepitus”22, p329 may have been missed and
this could potentially lead to an underdiagnosis of TMJ
osteoarthrosis in the present sample. However, studies on
radiographic changes of the condyle or fossa have not
found any correlation to symptoms and therefore may
merely reflect the normal remodeling process of the
TMJ.39-41 Given that TMJ osteoarthrosis diagnosis based
on the RDC for TMD is neither painful nor associated
with TMJ dysfunction, its clinical significance in the di-
agnosis and treatment of TMD is questionable.
Previous studies have highlighted significant psycho-
logical symptoms among FM patients.42-44 The FM
patients had elevated SCL-90-R scores on somatiza-
tion, obsessive-compulsive, and depression symptoms
subscales as defined by a subscale score of 63 or higher.
Of interest were elevated subscale scores among FM
patients for somatization (P ? .02) and obsessive-
compulsiveness (P ? .009) compared with the FBS
group. Studies comparing psychosocial findings be-
tween patients with FM and patients with rheumatoid
arthritis have suggested an association between FM and
somatization45,46 and obsessive compulsiveness.47 It
has been established that FM patients present with
multiple symptoms given the comorbidities associated
with the syndrome, i.e., pain, sleep disturbances, fa-
tigue, and so forth.48,49 The multiple symptoms of FM
may be expressed as somatization and this in turn may
result in an internal focus on one’s health. The reverse
is also likely whereby internal focus on one’s health
may lead to somatization. This preoccupation with in-
ternal somatic states may manifest itself as elevations
of depression and obsessive-compulsive symptoms in
an attempt to cope with the FM symptoms. Thus ob-
sessive-compulsive symptoms may represent cognitive
and behavioral adaptation to pain. Compromised cog-
nitive, affective, and behavioral responses could result
from excessive long-term preoccupation with one’s
health. This may lead to dysregulatory psychopathol-
ogy and maladaptive behavioral responses.50 In turn,
maladaptive behavioral responses may lead to maladap-
tive physiological response, which is understood to be
a failure in inhibitory control and therefore may play a
role in perpetuating the symptoms of FM.51-54
The combination of the autonomic, attentional, and
affective systems into a dynamic functional and struc-
tural network enables the living system to self-orga-
nize.51,52 As described by Thayer and Lane,51 these
systems are likely modulated by inhibitory processes
that in turn enable sustained functioning of the living
system when confronted by stressors. Hence, in a com-
promised system such as that of FM patients, disinhi-
bition (inhibitory failure) in the face of changing envi-
ronmental demands may lead to maladaptive behavior
that, in turn, may hinder recuperation and normal func-
tioning.51 The lack of significant differences among
other SCL-90-R subscales between the 2 groups may be
because both FM43,44 and FBS55,56 are chronic debili-
tating conditions that are frequently associated with
In the present study, FBS patients exhibited an
elevation of the somatization score on the SCL-90-R.
Previous studies have suggested that abnormal preop-
erative psychological features including depression,
Volume 104, Number 2Balasubramaniam et al. 211
hysteria, hypochondriasis, conversion, and somatiza-
tion may predispose patients to greater postoperative
pain after lumbar disk surgery.57 Others have suggested
that FBS patients have “emotional problems” including
elevated depression and somatic pain scores.58,59 Nu-
merous studies have suggested poor outcomes involv-
ing reoperation of FBS patients with psychological
problems.60-63 Therefore, it is not surprising that FBS
patients in the present study exhibited elevation of the
somatization subscale score on the SCL-90-R.
Based on the PSQI total score, both the FM and FBS
patients were considered poor sleepers defined by a
PSQI total score higher than 5. Previous studies have
associated poor sleep quality with FBS.64,65 It has been
postulated that poor sleep may also contribute to the
pain complaint of FBS.65 Further studies on sleep dis-
turbances are needed to understand its role in FBS. On
the other hand, it has been well established that FM
patients frequently complain of disturbed, nonrefresh-
ing sleep.1,66 Likewise, healthy patients may express
FM-like symptoms if their normal sleep architecture is
disturbed.67 It is not understood whether increased pain
in FM patients may contribute to sleep disturbances or
sleep disturbances may result in increased pain among
FM patients.68 Interestingly, apart from FM patients
having a significantly larger score for use of sleep
medication, both groups of patients were not different
with respect to all other PSQI scores. Use of sleep
medication among FM patients is common and often
prescribed as part of the treatment for poor sleep related
to FM. Sedatives, such as benzodiazepines, zolpidem
tartrate, and zaleplon; antidepressants, such as amitrip-
tyline; and muscle relaxants, such as cyclobenzaprine,
are often used to improve sleep.69-71 Therefore, the
implied causative relationship of FM symptoms with
poor sleep (architecture) could explain the higher use of
sleep medications endorsed by FM patients compared
to FBS patients.
There is a strong relationship between sleep and
chronic pain.68,72-74 A previous study reported that
stage-4 sleep deprivation led to muscle tenderness and
stiffness in healthy subjects, but such musculoskeletal
symptoms were not observed following disruption of
the rapid eye-movement (REM) sleep. Therefore poor
sleep quality of the deeper sleep stages may be linked
to chronic pain conditions. This may be because of the
inability to restore the functions of the body systems
such as metabolic processes that typically occur in
deeper sleep stages.75 Although speculative, poor deep-
sleep quality may lead to musculoskeletal pain, which
in turn may contribute to a fragmented sleep cycle.
FM patients had significantly higher general, emo-
tional, physical, and mental fatigue scores than FBS
patients. FM has been shown to have fatigue-like symp-
toms1,19,49,66 and comorbidity with chronic fatigue syn-
drome.19,76-80 Both FM and chronic fatigue syndrome
are marked by a heightened sensitivity to physical and
psychological stress.49,66,81,82 Previous studies have re-
vealed that fatigue in chronic pain was related to symp-
toms of somatization and depression and to a far lesser
degree sleep disturbances.35,83 In fact, it has been re-
ported that somatization35,83 and depression83 are major
predictors of fatigue. It is likely that the multiple symp-
toms of FM such as widespread pain, fatigue, sleep
disturbances, and so forth may be the result of high
somatization and depression scores in FM. That is,
preoccupation with one’s health may manifest as ele-
vations of depression and somatization symptoms in an
attempt to cope with the FM symptoms. The failure to
cope may result in dysregulation of autonomic nervous
system and in turn compromised cognitive, affective,
and behavioral responses apparent as fatigue-like
symptoms.50,84 Maladaptive behavioral responses may
lead to maladaptive physiological response and there-
fore perpetuate the fatigue-like symptoms of FM.53,54
Interestingly, while sleep disturbances are frequently
reported by chronic pain patients, they are not thought
to be the cause of fatigue.83 Both the FM and FBS
patients had sleep disturbances based on the PSQI and
there were no significant differences between the 2
groups. Both FM and FBS patients revealed significant
correlations between several of the PSQI scores and
fatigue-related disturbances; however, the FM patients
were significantly more fatigued than the FBS patients.
This study is not in agreement with previous studies
that suggest that fatigue is unrelated to quantitative
measures of sleep.83,85 The multiple symptoms of FM,
which include widespread pain, somatization, depres-
sion, sleep disturbances, and fatigue, may actually lead
to and perpetuate a maladaptive physiological and psy-
Previous literature suggests that PTSD may coexist
with FM.86,87 Suggestions that the 2 entities exist be-
cause of care-seeking selection bias among FM pa-
tients, failure of FM patients to cope with life stress,
and confounding arousal symptoms between PTSD and
FM have been refuted.88 Although exploratory, it is
likely that FM and PTSD share psychobiological risk
factors.88 A significantly higher number of FM patients
(87%; P ? .036) than FBS patients (56%) reported a
stressful life event. Of those FM patients who reported
a stressful life event, 42.3% were PTSD positive based
on a score of greater than 41 on the PCL-C. Previous
studies reported that more than 50% of FM patients had
significant levels of PTSD symptoms.86,87 Sherman
et al.86 found in a sample of FM patients that pain level,
disability, and affective distress was greater in those
patients reporting PTSD symptoms than those who did
Balasubramaniam et al.
not report such symptoms. Sherman and colleagues86
suggested that PTSD-like symptoms may influence the
adaptive ability of FM patients. Therefore, failure to
assess the presence of these symptoms may impede
successful outcomes. Further studies are required to
elucidate the relationship between FM and PTSD.
The high prevalence of TMD and psychosocial dis-
tress among FM patients could be manifestations of
somatization, depression, a dysfunctional hypothalamic-
pituitary-adrenal (HPA) axis, and/or a dysregulated auto-
nomic nervous system and in turn result in alterations of
the peripheral and central pain facilitation and inhibi-
tory pain mechanisms.81,89 Therefore, a facilitation or
failure in inhibition of nociception may lead to central
sensitization and increased pain perception. This in turn
may affect the dynamic equilibrium of the system and
shift it from an adaptive physiological state to that of
dysfunction and pathology.51,52 This may further ex-
plain the comorbidity of FM with other conditions such
as chronic fatigue syndrome, irritable bowel syndrome,
and interstitial cystitis, which may be related to a re-
duction in pain threshold and tolerance mediated by
central nervous system mechanisms. In addition, these
conditions are marked by a heightened sensitivity to
both physical and psychological stress.49,66,81,82 There-
fore, the multiple-symptom presentation of FM, which
may include pain, nonrestorative sleep, fatigue, depres-
sion, obsessive-compulsiveness, and somatization, is
likely influenced by maladaptive physiological and
Sixty-six percent of the FM patients were unem-
ployed and 53% were receiving disability. Previous
studies have reported that 30% of FM patients worked
shorter hours or less physically demanding jobs and
15% received disability from inability to work.90-92
Another study reported that 41% of patients were un-
able to work.9 The large number of unemployed sub-
jects and subjects receiving disability in the current
study may be a result of the recruitment protocol.
Patients in this study were recruited from a Physical
Medicine and Rehabilitation clinic and an FM work-
shop possibly targeting subjects who are actively seek-
ing treatment and who may have greater severity of the
A previous study reported that 22% of FM patients
smoke tobacco and the study adjusted for age and
education level.93 Interestingly, in the current study
only 1 FM patient used tobacco and this was signifi-
cantly different compared with FBS patients. Recent
data on the prevalence of smoking in the United States
reported that 23.4% of males and 18.5% of females in
the total population smoke.94 Therefore, a rational ex-
planation of the low prevalence of tobacco use among
FM patients in this study is difficult. Interestingly, 42%
of the FBS patients in this study used tobacco. It has
been suggested that heavy tobacco use is common
among FBS patients24 and is a major risk factor for
developing lower back pain95,96 as well as failure of
bony union associated with FBS.97
The present study has limitations in spite of its pro-
spective design. A major concern of this study was the
small sample sizes in each of the groups. Therefore,
detailed statistical analysis of the study variables was
not possible. Another concern was that the study in-
volved FBS patients as a control group, which many
consider a poorly defined clinical condition.23-25 Simi-
larly, much debate persists on whether FM as a clinical
condition exists. As a result, comparisons between 2
poorly defined conditions may have led to questionable
findings and interpretation. On the other hand this was
the first study that investigated the prevalence of TMDs
in FM that employed a chronic pain population sample
Because of the recruitment protocol, the participating
patients may not represent a sample of the general
population. All patients were actively seeking treatment
for their condition at a tertiary care center and this may
have resulted in an overestimation of the prevalence of
TMD among FM patients. In addition, the prevalence
of psychosocial distress in both FM and FBS patients
may not be representative of the subjects with these
conditions in the general population. Therefore, the
patients in this study could represent a selective pain
population compared with those patients seen at a gen-
With respect to the prevalence of TMD, the RDC
embraces all TMD diagnoses, including painless click-
ing and crepitation of the TMJs. As previously dis-
cussed, asymptomatic clicking of the TMJ and TMJ
crepitation may be coincidental and not be of clinical
relevance. Therefore, this may have led to an overesti-
mation of the prevalence of TMD in FM patients.
The present study replicated and extended previous
investigations addressing the relationship between
TMD and FM. This study confirmed our hypothesis
that the prevalence of TMD is greater among FM
patients than among FBS patients. High levels of psy-
chosocial distress and PTSD-like symptoms were
found in both the FM and FBS patients, but several
measures of psychological distress and dysfunction
were significantly higher in FM patients than in FBS
patients. We speculated that these results could be
because of facilitation or inhibitory failure of pain
mechanisms or maladaptive coping mechanisms, which
Volume 104, Number 2Balasubramaniam et al. 213
might lead to dysfunction of the HPA axis and dys-
regulation of the autonomic nervous system. Thus, dys-
function of the HPA axis and dysregulation of the
autonomic nervous system may be linked to the high
prevalence of TMD and significant psychosocial dis-
tress among FM patients.
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Ramesh Balasubramaniam, BDSc
Department of Oral Medicine
Robert Schattner Center
University of Pennsylvania School of Dental Medicine
240 South 40th St
Philadelphia, PA 19104
Balasubramaniam et al.