Original Research
Sleep Quality in Chronic Pain Patients
Kemal Sayar, MD1, Meltem Arikan, MD2, Tulin Yontem, MD3
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Objective: Chronic pain patients have been reported to complain about poor sleep quality. Research aimed at delineating the predictors of poor sleep has produced conflicting results. Depressive mood and pain severity are the most frequently encountered predictors. This study aimed to find out whether chronic pain patients differed from healthy control subjects who had no pain on subjective sleep quality measures and, if so, which factors contributed most to poorer sleep quality.
Method: We compared 40 patients with chronic pain who met inclusion criteria with 40 healthy control subjects on the measures of sleep quality, anxiety, and depression. The predictors of sleep quality were investigated with multiple regression in the pain group.
Results: Chronic pain patients had higher scores than did healthy control subjects on the Beck Anxiety Scale, the Beck Depression Inventory (BDI), and the Pittsburgh Sleep Quality Index (PSQI). At the bivariate level, pain intensity, anxiety, and depression correlated significantly with poorer sleep quality. At the multivariate level, depression was found to be the only significant factor correlating with the quality of sleep, and the model explained 34% of the variance.
Conclusions: Chronic pain patients suffer from poor sleep quality—a function of depressed mood rather than pain intensity, duration, or anxiety. However, it is difficult to draw a causal relation in this relatively small sample size. Besides, our study sample comprised a mostly psychiatric population and may not represent the general group of patients with chronic pain.
(Can J Psychiatry 2002; 47: 844–848)
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Clinical Implications
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Chronic pain patients suffer from poorer quality of sleep than do healthy control subjects.
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This poorer sleep quality is a function of depressed mood rather than of pain duration, intensity, or anxiety.
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Antidepressant therapy may be effective in relieving sleep complaints associated with chronic pain.
Limitations
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Self-reported data were presented on sleep quality. Subjective and objective measures of sleep quality need not correlate well with each other.
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The findings are cross-sectional in nature, and the direction of causality cannot be determined definitively.
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The sample size is relatively small to generalize.
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Key Words: chronic pain, sleep, depression, anxiety, pain intensity
Résumé : La qualité du sommeil chez les patients aux douleurs chroniques
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It has been estimated that between 50% and 88% of patients with chronic
nonmalignant pain disorders have significant sleep complaints (1–4). Disturbed
sleep may interfere with the daily functioning of the patients, and poor
sleep may be a contributing factor, to the extent that it increases one’s
sensitivity to pain (5,6). It has been suggested that sleep disturbance
in chronic pain patients may increase pain sensitivity and create a self-perpetuating
cycle of sleep disruption, increased pain, and depression (7). Chronic
pain patients often experience significant mood disturbance along with
sleep disturbance (3). Psychological distress has been found to be more
intense among chronic pain patients who also report poor sleep than in
those without concomitant sleep disturbance (1). Various studies have uniformly
found that pain severity and the level of depressive symptoms associate
with the degree of sleep impairment (1,2,8,9). Some of these studies have
found that depression severity, as opposed to pain severity, is more associated
with sleep disturbance in patients with chronic pain (1,2,9). Other studies
suggest that depression severity may not be the primary mediating variable
(3,10). Presleep cognitive arousal is also reported to be the primary predictor
of sleep quality in chronic pain patients (4). In one study, physical functioning,
duration of pain, and age were found to be more important than were pain
intensity and depressed mood in contributing to decreased overall sleep
quality and sleep latency (11). We wanted to delineate the predictors of
sleep quality in a sample of chronic pain patients. Further, we wanted
to see whether chronic pain patients differed from healthy control subjects
with no pain on subjective sleep quality measures and, if so, which factors
contributed most to poorer sleep quality.
Method
Subjects
A total of 40 eligible consecutive chronic pain patients were evaluated
in Vakif Gureba Training and Research Hospital (VGTRH), Istanbul, in the
first 6 months of the year 2000. VGTRH is a tertiary care hospital with
600 beds, where the first author served as a consultant psychiatrist for
3 years. Referral sources included general medicine clinics and primary
care physicians in the community. Patients suffering from chronic nonmalignant
pain (n = 40) were compared with 40 healthy control subjects without pain.
The pain sample consisted of 32 women and 8 men, with a mean age of 37.1
(SD 11.9) years. Of the patients, 26 suffered from headaches, 12 from backaches,
and 2 from neck aches. The main pain duration was 8.4 (SD 6.7) years. Patients
having a psychotic disorder, cognitive impairment, medical illness known
to interfere with sleep (that is, heart disease or chronic obstructive
pulmonary disease), and substance use disorder (current or within the 3
months) were excluded from the study. Also excluded were patients who had
been taking medications that alter sleep or who were illiterate and unable
to complete the questionnaires. None of the eligible patients who were
asked to participate in the study refused, and they all gave informed consent.
The interviewers collected sociodemographic data. Individuals completed
self-report questionnaires that measured pain, depression, anxiety, and
sleep quality.
Measures
The Pittsburgh Sleep Quality Index (PSQI) is a self-rated questionnaire
that provides an index of sleep quality for a 1-month interval (12). The
PSQI comprises 19 self-rated questions and is an instrument with established
reliability and validity. These 19 items are grouped into 7 component scores,
each weighted equally on a 0-to-3 scale. The 7 component scores are then
totalled to provide a global PSQI score, which has a range of 0 to 21,
with higher scores indicating worse sleep quality. The PSQI has been shown
to be valid and reliable in Turkish population studies, with a Cronbach
alpha of 0.80 and test–retest reliability of 0.93 to 0.98 (13). We took
the global score as an index of sleep quality in our study. We also took
scores > 6 on PSQI as an indicator of poor sleep quality.
The Beck Depression Inventory (BDI) is a 21-item, self-report questionnaire
that assesses severity of depression (14). Individuals are asked to rate
themselves on a 0-to-3 spectrum (0 = least and 3 = most), with a score
range of 0 to 63. The total score is a sum of all items. It was shown to
be valid and reliable in Turkish (15).
The Beck Anxiety Inventory is a 21-item, self-report questionnaire (16)
in which each item is rated on a 4-point Likert scale ranging from 0 (not
at all) to 3 (severely, I could barely stand it). The total score ranges
from 0 to 63. It was shown to be valid and reliable in Turkish (unpublished
data).
The patients used a Visual Analog Scale (VAS) to rate the pain intensity.
A 10-cm VAS was used with anchors of “no pain” and “pain as bad as it
could be.” Most studies that compare VAS with numerical and verbal ratings
conclude that the VAS or the numerical ratings are statistically preferable
to the verbal rating scales (17).
Patients also rated their disability on a scale from 0 to 4, with higher
scores indicating more disability.
Data Analysis
Groups were compared at the bivariate level using t-tests for continuous
variables and chi-square tests for categorical variables. Bivariate relations
between continuous variables were examined with Pearson product-moment
correlations (r). Multiple linear regression analyses were used to predict
scores on the PSQI. The pain group was dichotomized as good and bad sleepers
and compared. The SPSS carried out all the procedures (18).
Results
Sociodemographic and Psychological Characteristics of Sample
Table 1 presents the sociodemographic and psychological characteristics
of the total sample, as well as by group. Of the total sample, 79% were
women, the mean age was 37 years, 75% were married, and 40% were employed.
Chronic pain patients were significantly less educated than were healthy
control subjects, but their economic status was similar. Chronic pain patients
had higher scores than did healthy control subjects on the Beck Anxiety
Scale, the Beck Depression Inventory, and the PSQI.
Predictors of Sleep Quality
Tables 2a and 2b illustrate 2 multiple regression models of sleep-quality
determinants. Pearson product-moment correlations between the PSQI and
age, sex, pain duration, pain intensity, and the scores on the different
scales are presented in the first column of both tables. Table 2a shows
the first model. At the bivariate level, pain intensity, anxiety, and depression
correlated significantly with poorer sleep quality. At the multivariate
level, depression was found to be the only significant predictor of the
poor sleep quality in Model 1, and the model explained 34% of the variance.
Table 2b shows the second model. At the bivariate level, age, sex, and
pain duration did not significantly correlate with poorer sleep quality.
Again, depression was found to be the only significant predictor of the
poor sleep quality in Model 2, and the model explained 31% of the variance.
When chronic pain patients were dichotomized as good and bad sleepers according
to a cut-off score of 6 in the PSQI, bad sleepers (n = 23, PSQI scores
> 6) scored significantly higher on the BDI than did good sleepers (n =
17) (23.6 [SD 12.9] vs 16.1 [SD 7.6]; t = 2.76, P = 0.009). There was no
significant statistical difference on the measures of anxiety, pain intensity,
disability, and pain duration between good and bad sleepers.
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