Abstract
Background: Little is known about chronic low back pain (CLBP) in combination with widespread musculoskeletal pain (WMP).
Objective: This study examined factors that may be common to these conditions, with the objective of detecting factors that could improve the course of these diseases.
Design: This was a prospective case control study.
Patients and Intervention: A group of patients with CLBP and WMP (CLBP+WMP group, n=97) was compared with a group of individuals who were pain-free and without a history of musculoskeletal problems (control group, n=97) and with a group of patients with CLBP but without WMP (CLBP-only group, n=52). The mean age of the participants was 42.9 years (SD=8.74); 76% were women, and 24% were men.
Measurements: A total of 74 variables were measured, including sociodemographic, physical, and psychosocial variables. After univariate examination for group differences and analyses of variables available for all 3 groups, logistic regression on selected factors was performed. The α level was set at .05, but was adjusted to avoid randomly significant results.
Results: For a number of variables, significant differences among the 3 groups were observed. For regression model 1 for the CLBP+WMP and control groups, 4 out of 9 variables showed significant likelihood tests: income (lower in the WMP group), depression, anxiety, and fear-avoidance behavior. For regression model 2, 2 out of 13 variables showed significant likelihood tests: endurance capacity (more in the CLBP+WMP group) and balance capability (worse in the CLBP+WMP group). The models predicted at least 91.2% of all cases to the correct group. The regression analysis regarding the CLBP+WMP and CLBP-only groups predicted 86.7% of all cases to the correct group. Three out of 10 variables showed significant likelihood tests: high disability, fear-avoidance behavior, and number of treatments.
Limitations: Some variables in testing the patients with WMP and the individuals who were pain-free were not used with the patients with CLBP only.
Conclusions: Patients with CLBP and WMP should be examined for indicated physical and psychosocial factors. Therapeutic management should consider them in the early stage of the disease. These findings also might apply to patients with fibromyalgia or myofascial pain.
Diagnosis, treatment, and the primary mechanisms underlying the etiopathogenesis of chronic low back pain (CLBP) in combination with widespread musculoskeletal pain (WMP) remain elusive, despite increased research. In the literature, genetic factors, affective disorders, and physical and psychological stressors are listed as the factors of CLBP and WMP.1–3 Therefore, our study examined the main factors associated with CLBP and WMP, comparing a group of patients with CLBP and WMP with a group of individuals who were pain-free and with a group of patients with CLBP but without WMP. Generally, patients with chronic widespread musculoskeletal pain (CWMP) also have CLBP. The aim of this study was to identify a pattern of specific variables associated with CLBP and WMP by comparing a number of variables in these study groups. We surmised that, with timely treatment of these factors, the progression rate of WMP could be decreased.
Low back pain (LBP) in combination with WMP indicates reduced functional ability and predicts long-term work disability. According to Natvig and colleagues,4,5 this is not true of localized pain. When patients report recent LBP of low intensity during an initial visit to a general practitioner, it is a predictor that their back pain will be of short duration,6 whereas a report of widespread pain indicates a prognosis of LBP of longer duration can be expected.7
Psychosocial factors are known to be associated with LBP and WMP, but the significance of these symptoms in the general population is not known.8 In patients with CLBP, the fear of injury is significantly correlated with disability. It has been suggested that people with CLBP as a part of WMP may be the major cause of the burden that chronic nonspecific LBP has on family members and on society.9
Establishing a diagnosis and evaluating the effects of therapy in patients with CWMP may be difficult because of the multifaceted nature of their complaints and possible overlap with other chronically painful conditions.10 Sometimes diagnoses from different medical experts of a myofascial pain syndrome, a somatoform pain disorder, or a fibromyalgia syndrome (FMS) may be used synonymously or are overlapping with CWMP.
Myofascial pain syndrome, a painful musculoskeletal condition, is characterized by the development of myofascial trigger points that are locally tender when active and which refer pain through specific patterns to other areas of the body. Myofascial pain often is described as occurring in a rather limited area of the body, but when such trigger points exist, pain is more dispersed. Some authors11 noted that myofascial pain syndrome must be distinguished from fibromyalgia.
A somatoform pain disorder is diagnosed in patients with pain for at least 6 months and with strong evidence that psychological factors have caused or are maintaining the pain. Many of these patients have depressive illnesses, and, in some cases, major depression may be the root cause. Rarely do patients self-report psychological stress factors as a reason for their pain or see a correlation, but validated instruments for the measurement of depression do exist, such as the Hospital Anxiety and Depression Scale and the General Depression Scale used in this study. Sometimes, such symptoms may not be easily differentiable from those of patients with FMS and WMP.
Patients with FMS also report a defined pattern of widespread pain and at least 11 of 18 specific tender points, which should be painful to palpation according to the criteria published by the American College of Rheumatology.12 This definition has been questioned by some authors.13,14 Noteworthy also are some analogies between WMP and FMS with respect to the psychosocial factors.
Because of the variety of terms and the similarity of these diseases, this investigation was focused on patients with CLBP in combination with WMP. By comparing patients with CLBP and WMP with individuals who were pain-free, we established important factors that differentiate between these groups and between the groups with CLBP with and without WMP. We tested for associations and interactions among these patient groups.
Although several accumulative associated factors have been identified in previous studies, little is known about the combination of LBP and WMP.7,10 No unified pathophysiology for the development of this pain syndrome has been found. Only a few studies are available that indicate any correlations in the developments of CLBP and WMP7; even less information exists regarding early signs of CLBP and WMP. Thus, this pain pattern represents a unique therapeutic challenge.
To our knowledge, no detailed survey comparable to this study exists that has examined the medical, clinical, psychological, and psychosocial factors of patients with CLBP and WMP. Physical therapists and other professional groups engaged in the management of spinal problems should trace these factors to provide a better and specific treatment for this pain pattern.
Method
Study Population and Sampling
A group of patients with CLBP and WMP (CLBP+WMP group, n=97) was compared with a group of individuals who were pain-free and who stated that they were free from any painful musculoskeletal disorders during at least the preceding 3 months (control group, n=97) and with a group of patients with CLBP but without WMP (CLBP-only group, n=52). The study was carried out over a period of 18 months in a center specializing in painful musculoskeletal diseases. Primary health care physicians, specialists in physical medicine and rehabilitation, pain specialists in orthopedics, neurologists, and psychiatrists were encouraged to refer patients with back disorders in combination with widespread pain to participate in the CLBP+WMP group. Additional individuals were drawn from among the resident patients of a pain clinic. All participating physicians were asked to recommend only patients with nonspecific CLBP and WMP. All patients were asked to bring their medical reports to the screening. At the screening, the patients’ medical reports were reviewed by 1 of 3 experienced physicians in our pain clinic. A physical examination of the spine and the upper and lower extremities was conducted. Exclusion criteria were: inflammation, radiculopathy, spinal tumor, acute infection, fracture, previous spine surgery, rheumatic disease, or any other specific or systemic causes of their complaints. People with a history of or clinical, radiological, or laboratory signs of the above-mentioned conditions and diseases (operant organic diseases) were excluded from the study and referred back to their general practitioner or to a specialist for further diagnostic or therapeutic measures.
Candidates were included in the group of patients with CLBP and WMP only if they had CLBP for longer than 3 months, pain in at least one area of the upper body, and pain in the cervical or thoracic spine and in both sides of the body (pain topography was examined by the pain drawing method). The pain pattern of this pain topography was the primary inclusion criteria for the CLBP+WMP group. Low back pain was defined in accordance with a modified figure of Kuorinka et al,15 which presents LBP in a span between the lower ribs and the lower gluteal folds. Of 108 such potential participants invited for screening, 97 adults who fulfilled the inclusion and exclusion criteria were selected to participate in this study. Five people did not fulfill the inclusion and exclusion criteria. Three volunteers were excluded because they could not communicate effectively. Another 3 individuals, although eligible, decided not to participate.
Patients with CLBP and WMP were compared with the patients in the pain-free control group. To generate interest in this study, individuals who were pain-free were entered in a lottery (but no other payments were made). There were no dropouts after screening for the CLBP+WMP and pain-free control groups. A possible source of selection bias could be that the people in the pain-free control group were individuals who were willing to participate in a study, although they had no musculoskeletal complaints.
Finally, a group of patients of comparable age with CLBP but without WMP and participating in a back school program was used as a comparative group; their data were used in a secondary analysis. For this group, the same definition of CLBP and the same exclusion criteria were applied, as for the CLBP+WMP group. Individuals of all 3 groups were excluded if they were younger than 18 years of age or older than 55 years of age. The patients in all 3 groups signed informed consent statements prior to participating in the study.
Measurements
Participants in all 3 groups completed a comprehensive examination, which included sociodemographics, pain parameter history, disability, nonmusculoskeletal comorbid conditions, psychosocial factors, and a clinical assessment. For the patients in the CLBP-only group, fewer variables were evaluated. The tests were documented for each group as shown in Table 1.
Tests Conducted in the 3 Groupsa
The social history included the patient's family and work environments before and during the time of the investigation. Most data were collected by validated questionnaires. Completion of the questionnaires was voluntary, and the participants were assured that their anonymity would be protected. Questions regarding sensitive factors such as sexual molestation or violence in the family were asked in a structured interview by a trained female psychologist with more than 15 years of experience. To avoid effects of fatigue, rest periods were made available during the test procedure. The mean duration of the whole examination was 85 minutes. The groups underwent a clinical functional assessment by a medical doctor. Identical variables that were considered for the CLBP+WMP and CLBP-only groups are shown in Table 1.
Pain history.
To examine pain topography, the pain drawing method was used.16 A silhouette modified to the figure of Kuorinka et al15 (viewed from the back), which illustrates 9 areas of the human body, was presented to the participants. Each area was marked with a number, and the participants were instructed to mark the number of the areas where they felt pain. Furthermore, they were asked for the topography of the primary pain as well as pain with the second- and third-highest intensities. Intensity of the primary pain at the time of the examination was assessed using the 101-Numeric Rating Scale (101-NRS).17
Disability.
Assessment of the participants’ disability because of LBP was based on a disease-specific functional status questionnaire, the Oswestry Low Back Pain Disability Index.18–20 High scores indicated high disability. The scores were converted into percentages, and disability was categorized as “minimal,” “moderate,” “severe,” or “crippled.”18
Health-related quality of life.
General health was assessed by a validated German version of the Medical Outcomes Study 36-Item Short-Form Health Survey (SF-36).21 The SF-36 measures functional health and well-being in 8 separate dimensions (possible range of scores=0–100, where 0 represents maximal health restriction and 100 represents no restrictions). These dimensions may be reduced to 2 scores (ie, physical and mental component summary scores). Averaged data have been published for individuals with back pain (physical component summary: X̄=44.73, SD=10.61; mental component summary: X̄=48.25, SD=10.95).22 The SF-36 manual also includes age- and sex-specific norm values.
Psychometric questionnaires.
The participants were asked to complete a battery of psychosocial questionnaires designed to elicit specific information on a wide variety of psychosocial dimensions. The following validated psychometric questionnaires were used for the CLBP+WMP and control groups and partly for the CLBP-only group (Tab. 2). The General Depression Scale23 is an adaptation of the Center of Epidemiological Studies Depression Scale.24 It was specifically developed for research on non–clinically depressed samples. Higher scores indicate more symptoms of depression; a score higher than 23 points indicates a clinically relevant depression.
Psychological Questionnaires and Results of the Interview of the Participants With Chronic Low Back Pain and Widespread Musculoskeletal Pain (CLBP+WMP Group) and the Individuals Who Were Pain-free (Control Group)a
Anxiety was assessed by the “trait” scale of the State-Trait Anxiety Inventory.25 High scores indicate a general tendency to respond with anxiety to perceived threats in the environment.
Somatization was examined by the somatization scale of the Symptom-Checklist-90-Revised instrument (SCL-90-R).26,27 High values indicate more-severe symptoms.
The Fear-Avoidance Beliefs Questionnaire (FABQ)28,29 was developed to evaluate individual beliefs about how physical activity affects LBP. High values indicate greater fear and increased avoidance behavior. The validated version (in the German language) that was used for this study, according to the recommendations of the author,29 does not allow a differentiation in fear-avoidance behaviors concerning physical activity in general and at work.
Pain coping strategies and reactions to pain were assessed with 2 parts of the Kiel Inventory of Coping With Pain.30 This inventory includes different scales (listed in Tab. 2) comprising cognitive and emotional reactions to pain. High values indicate less coping ability.
Interview.
A female psychologist interviewed the participants regarding personal issues such as conflicts with a partner, stress or harassment at work, and sexual molestation. Questions were summarized into variables of psychological stress from earlier years and current stress (Tab. 2). Possible stresses from earlier years are sexual molestation, violence in the family, and eating disorders. Current strains registered were mobbing/stress and harassment at work, unfair treatment at work, burden due to pedagogical problems, self-perceived double or more-excessive burden, and conflicts with a partner.
Clinical assessment.
On entering the study, each participant of the CLBP+WMP and control groups underwent a clinical functional assessment that included the parameters listed at the end of Table 3. The extent of the clinical assessment of the participants in the CLBP-only group was not identical to that of the other groups and served initially to exclude signs of radiculopathy (straight-leg-raising test, manual muscle testing, reflexes, pinprick, and vibration).31
Characteristics of the Participants With Chronic Low Back Pain and Widespread Musculoskeletal Pain (CLBP+WMP Group) and the Individuals Who Were Pain-free (Control Group)a
All tests were performed for each group in the same way. Assessment of head rotation (cervical spine) was carried out using the Cervical Range of Motion (CROM)* goniometer.32 The straight-leg-raising test was conducted in the supine position for both legs.33 The examiner lifted the patient's leg (into hip flexion) as much as tolerable while keeping the knee straight. The straight-leg-raising test was described as a “positive Lasegue sign” if pain in the sciatic distribution was reproduced between 30 and 70 degrees of passive flexion of the straight leg.34 Individuals (of all 3 groups) with a positive Lasegue sign were excluded from the study. Fingertip-to-floor distance was used as an indicator for spinal flexion and was assessed by asking the participants to bend forward as far as possible. For the interscapular fingertip distance measurement, the participants were asked to reach with both hands into the interscapular region (ie, one hand from below in the direction of the neck and the other hand from above in the direction of the sacrum). The distance between the tips of the third fingers of both hands was measured. In cases in which a participant could overlap her or his fingers, the measurement became minus. Hypermobility was evaluated according to the method of Beighton, a system to quantify joint laxity and hypermobility.35 It uses a 9-point system: one point for passive dorsiflexion of each fifth finger greater than 90 degrees, one point for passive apposition of each thumb to the flexor surface of the forearm, one point for hyperextension of each elbow greater than 10 degrees, one point for hyperextension of each knee greater than 10 degrees, and one point for ability to place the palms on the floor with the knees fully extended. The higher the score, the higher the laxity. A Beighton score greater than 4/9 is indicative of generalized joint hypermobility.
The ability to stand on one leg in a standardized position (arms crossed in front of the body, eyes closed) was measured in seconds, with a maximal duration of 60 seconds and with one attempt for each side. The 18 well-defined tender points were palpated for testing for pain at 4 kp/cm2 as indicated by the American College of Rheumatology.12 For that purpose, a Fisher palpometer† was used. All tests that could be performed to the left and to the right were examined for both sides and then averaged if no significant difference between right and left sides was noted.
Data Analysis
Descriptive statistics were used to present the basic features of the data. Means and standard deviations or medians and ranges were computed, depending on the scaling of the data for quantitative variables. Percentages were computed for categorical variables.
To test the quantitative dependent variables for group differences, Student t tests or one-way analyses of variance (ANOVAs) were performed, depending on how many groups were tested. The assumptions for these tests are: (1) normal distribution of the independent variables and (2) equal variances among the groups of the independent variables. The validity of the assumption of equity of variances was established with Levene tests, and normal distribution was controlled visually by inspecting the histograms. As post hoc tests for pair-wise comparisons, Scheffé tests were performed. It became apparent that the adoption of the homogeneous variables was not infringed; however, the distribution of the variable of years since onset of pain could not be validated as being congruous. The variables of number of comorbidities, number of psychological stresses from earlier years, number of present stresses, number of treatments, number of tender points, number of children, and number of people living in the same household could not meet the criterion of the interval scaling.
Calculations for the latter variables were done with parameter-free methods. The Mann-Whitney U test for significance or, in case of a comparison between groups, the Kruskal-Wallis test was used to test for significant differences among quantitative variables that did not reach the data level for the interval scaling or that could not meet one or both of the conditions for the t test or the variance analysis. Footnotes in the tables indicate the respective methods used. Differences among categorical variables were computed using the chi-square statistic.
The chosen level of significance was P≤.05. To avoid randomly significant results because of the large number of variables, alpha adjustment was performed using the Bonferroni method.36 The significant P value after alpha adjustment for the between-groups comparison was .001, using the formula α′=α/m, where m corresponds to the number of the test procedures that are included in the test of the hypothesis. Correlations were examined with the Pearson product moment correlation. For ordinally scaled data, a Spearman rho was computed. This was the case with all correlations, including number of treatments, number of tender points, and years since onset of pain.
For further evaluation, logistic regression analyses were computed, using the forward likelihood ratio approach. Variables showing significance in the univariate analysis were entered as independent variables. In logistic regressions, independent variables can be continuous or categorical. To avoid biased estimates, the data were tested for multicollinearity among the predictors with the scatterplot procedure. Overall fit was tested by the Hosmer and Lemeshow goodness-of-fit statistic. A predictor was seen to be useful for the model if the change of −2 log likelihood was significant for the respective variable. Odds ratios and their 95% confidence intervals were computed for the resulting variables, showing the independent effect of each factor.
Three models were calculated, each including selected ranges of topics.37 The first model included the social-demographic and psychological variables, such as age, income, education, anxiety, fear-avoidance behavior, depression, somatization, and numbers of stresses and comorbidities.
The second model dealt with the physical characteristics and different variables regarding reactions to pain: age, sex, one-leg-stand time (left and right legs averaged), fingertip-to-floor distance, active head rotation, interscapular fingertip distance measurement, straight-leg-raising test (left and right legs averaged), body mass index (BMI), helplessness and hopelessness, disability, endurance capacity, psychical cause attribution, and nonverbal pain reaction.
An additional model evaluating the CLBP+WMP and CLBP-only groups included sex, disability, fear-avoidance behavior, education, pain intensity, health-related quality of life, extent of employment, number of treatments during the preceding 3 months, and number of comorbidities.
A power analysis was conduced for the main outcome variable of disability. With regard to the contents, it seemed appropriate to include only the data of the CLBP+WMP and CLBP-only groups because it became evident that, by supposing an alpha error of 5%, the number of study participants (97+52=149) was sufficient to attain a power of >0.999 with the extant mean value differences. All statistics were computed using Statistica, version 7.0.‡
Role of the Funding Source
This study was supported by the Austrian Federal Ministry of Women and Health.
Results
Variables Evaluated for All 3 Groups
After screening for study criteria, a total of 246 people (mean age=42.9 years, SD=8.74), 76% women, 24% men) were eligible for the study. Descriptive statistics for the demographic data, number of nonmusculoskeletal comorbidities, and results of the SF-36, the FABQ, and the Oswestry Low Back Pain Disability Index are presented in Table 4. Marital status did not differ significantly among the 3 groups (P=.069) in contrast to the characteristics of sex (P=.009), education, extent of employment, and number of comorbidities, which showed significant differences among the groups (P≤.000).
Descriptive Characteristics of Variables in All 3 Groupsa
The univariate analyses of data for extent of employment showed significant differences among all 3 groups and between the CLBP+ WMP and CLBP-only groups and the control group for education and number of comorbidities (P≤.003). No significant differences were found between the CLBP-only group and the control group for education (P=.104) and number of comorbidities (P=.853).
The ANOVA results for all 3 groups are shown in Table 5. According to the Scheffé post hoc test, the SF-36 physical component summary score and the results of the FABQ differed significantly among all 3 groups. For age, a significant difference existed only between the CLBP+WMP and control groups (P=.019). For BMI, significant differences were found between the control group and the CLBP+WMP group (P≤.000) and the CLBP-only group (P=.001) but not between the CLBP+WMP and CLBP-only groups (P=.891).
Results of the Analyses of Variance for Variables of the 3 Study Groupsa
Finally, the Scheffé test showed significant differences for the SF-36 mental component summary score between the CLBP+WMP group and the CLBP-only and control groups (P=.000), whereas no significant difference was found between the CLBP-only group and the control group (P=.571).
Variables Evaluated for the CLBP+WMP and Control Groups
A number of remaining sociodemographic characteristics and clinical data of the CLBP+WMP and control groups are presented in Table 3. Significant differences between these 2 groups became apparent. For one-leg stand, no significant differences were found between patients with LBP and pain in a leg and patients with LBP but without pain in a leg (Mann-Whitney U test; left leg, P=.326; right leg, P=.589).
The results of the psychosocial questionnaires and the interview of the participants in the CLBP+WMP and control groups are shown in Table 2. Again, the questionnaires displayed significantly worse data for the CLBP+WMP group compared with the control group, except for some scales of the cognitive reaction to pain such as exaggeration (catastrophizing) or minimizing and for most of the coping reactions in pain situations. Furthermore, participants in the CLBP+WMP group reported significantly more psychological trauma in childhood and current stress.
Correlations performed for the CLBP+WMP and control groups are presented in Table 6. Significant correlations were found between number of tender points and depression (r=.253, P=.013) and between number of tender points and SF-36 physical component summary score (r=−.378, P<.000) in the CLBP+WMP group, whereas these correlations are not significant in the control group (correlation between number of tender points and depression: r=−.050, P=.629; correlation between number of tender points and SF-36 physical component summary score: r=−.080, P=.440).
Results of Correlations Calculated for the Participants With Chronic Low Back Pain and Widespread Musculoskeletal Pain (CLBP+WMP Group) and the Individuals Who Were Pain-free (Control Group)a
The results of the analyses for regression models 1 and 2 between the CLBP+WMP and control groups are presented in Table 7. The first and second models predicted 97.8% and 91.2%, respectively, of the patients to be included in the CLBP+WMP group according to the included variables. Compared with the control group, the participants in the CLBP+WMP group earned significantly less, had more depression, anxiety, and fear-avoidance behavior and had a higher endurance capacity and shorter one-leg-stand (Tab. 7). The other sociodemographic and psychological variables and clinical data were not important associated factors in the CLBP+WMP group compared with the control group.
Variables Evaluated for the CLBP+WMP and CLBP-Only Groups (Except for ANOVA Results)
The results for pain, disability, and number of treatments for the CLBP+WMP and CLBP-only groups are presented in Table 8. The participants in the CLBP+WMP group reported significantly higher pain intensities, more years since onset of pain, more disabilities, and a larger number of treatments than the participants in the CLBP-only group. Correlations calculated for several variables for these 2 groups are presented in Table 9. Concerning the topography of the primary pain between the CLBP+WMP and CLBP-only groups, neck pain was found to be the second most prevalent site (29.9% versus 21.2%) compared with LBP (43.3% versus 57%) and upper back pain (10.3% versus 1.9%). The regression analyses predicted 86.7% of the patients to be in the CLBP+WMP group and demonstrated for them a higher likelihood (P<.001) of an increased number of treatments and higher disability and fear-avoidance behavior (Tab. 10).
Variables Comparing the Participants With Chronic Low Back Pain and Widespread Musculoskeletal Pain (CLBP+WMP Group) and the Participants With Chronic Low Back Pain but Without Widespread Musculoskeletal Pain (CLBP-Only Group)
Results of Correlations Calculated for Participants With Chronic Low Back Pain and Widespread Musculoskeletal Pain (CLBP+WMP Group) and the Participants With Chronic Low Back Pain but Without Widespread Musculoskeletal Pain (CLBP-Only Group)a
Discussion
This is the first comprehensive evaluation investigating a large number of demographic, clinical, psychological, and psychosocial variables to determine the factors most commonly associated with CLBP and WMP. Logistic regression analyses were used to measure the strength of associations among the predictor variables (ie, the degree of risk to the participants in the study groups). The multivariate models suggest that low income, severe depression and anxiety, fear-avoidance behavior, higher endurance capacity strategies, and a shorter one-leg stand are predominantly associated with patients with LBP and WMP compared with individuals who are pain-free. Compared with the participants in the CLBP+WMP group, those in the CLBP-only group reported a greater number of treatments, higher disability, and increased fear-avoidance behavior. Because there is a paucity of descriptive literature examining patient cohorts with LBP and WMP, the results of this study can serve in future research as valuable comparison data regarding the many evaluated parameters.
Age, Sex, and Body Mass Index
At the mean ages of 43.2 and 44.6 years, respectively, the participants in the CLBP-only and CLBP+WMP groups were within the typical age range described by White and Harth38 to be at risk for chronic generalized pain. The mean age of the participants in the control group was 3.5 years less.
More women than men were in all 3 groups. In particular, the CLBP+WMP group differed significantly from the CLBP-only group with regard to the ratio of men and women. Some authors39,40 have noted that WMP and FMS are more prevalent in women than in men of comparable age. When comparing patients with chronic pain with the general population, women reported more-frequent and more-intense pain and other more-negative effects than men.41,42 There seem to be differences in how men and women think and feel about their pain.43 Regarding BMI, we found significant differences between the CLBP+WMP and CLBP-only groups and the control group but not between the CLBP+WMP and CLBP-only groups. Furthermore, a significant negative correlation was computed between the BMI and the SF-36 physical component summary score for the CLBP+WMP group but not for the CLBP-only group. These results correspond with those of Neumann and colleagues’ study of patients with fibromyalgia.44
CLBP and WMP and FMS
Study interpretations customarily refer to results of comparable investigations. Although current published material rarely references comparable studies of patients with CLBP and CWMP, it frequently references studies of patients with FMS, a condition not identical to but similar to the characteristics of the CLBP+WMP group in this study. Pain is a cardinal symptom of people with CLBP and WMP, as it is of individuals with FMS and myofascial pain syndrome.
Tender Points, CLBP and WMP, and FMS
According to the criteria for the classification of FMS published by the American College of Rheumatology,12 a typical pain pattern of at least 11 of the 18 well-defined tender points should be painful to palpation. In our study, we found a significant difference between the CLBP+WMP group and the control group regarding the tender points. However, there also were 20 participants in the CLBP+WMP group with fewer than 11 tender points and 2 participants in the control group with more than 11 tender points. These findings suggest that many, but not all, patients in our study met the criteria for FMS. Recent studies13,14 showed that 11 as the cut point for the number of tender points is arbitrary, and there remain overlaps with other pain syndromes such as chronic diffuse muscular pain and chronic fatigue syndrome. Furthermore, the value of different algesimetric methods has been questioned because clinical pain and experimentally induced pain differ in important ways.45 Some patients also have both FMS and myofascial pain.35 In the current study, the number of tender points correlated with different, but not all, variables for the CLBP+WMP and control groups in the same way (Tab. 6) (significant for depression and pain intensity and negatively significant for the SF-36 physical component summary score in the CLBP+WMP group but not significant for the control group). These results point to a minute differentiating uniform role of the tender points between the psychological and physical factors involved in the pathophysiology of WMP.
Income and Extent of Employment
In this study, low income was an important factor associated with the risk for CLBP and WMP compared to the individuals who were pain-free. Pertinent literature reports conflicting results regarding low socioeconomic status as a risk factor for CLBP.46–48 The Canadian community health survey (2000–2001) indicated income, age, depression, and functional interference with activities to be strongly associated with chronic pain in general.49 The London Fibromyalgia Epidemiology Study associated a lower household income with increased likelihood of having FMS.50 Another study concluded that FMS is linked to a substantially increased risk of medically certified work absenteeism due to sickness.51 Nearly one third of the patients with CLBP and WMP in our study were unemployed. This finding indicates that the risk of work loss, which is associated with a low income, seems to be high for patients with WMP and CLBP.
Bergman52 compared individuals with no chronic pain and patients with chronic regional pain, chronic widespread pain, and clinically defined FMS. He noted that belonging to a lower socioeconomic group and having a lower education correlated with the population with CWMP and FMS, conclusions that were obtained in our study as well by comparing patients with CLBP and WMP and individuals who were pain-free.
Disability
The Oswestry Low Back Pain Disability Index scores of participants in the CLBP+WMP and CLBP-only groups differed significantly. Fifty-nine (60.8%) of the participants in the CLBP+WMP group were in the “moderate” disability category and 26 (26.8%) were in the “severe” and “crippled” disability categories, whereas 9 (17.9%) of the participants in the CLBP-only group were in the “moderate” disability category and 2 (3.8%) were in the “severe” disability category. These findings suggest that particularly the patients with only CLBP were coping rather well in their daily activities despite their chronic illness. Disability correlated significantly with pain intensity and fear-avoidance behavior in both the CLBP+WMP and CLBP-only groups, whereas disability and number of years since onset of pain correlated negatively in the CLBP+WMP group but not in the CLBP-only group. In contrast to our results, a less-significant association between disability and pain intensity in patients with CWMP was described in a study identifying commonalities among the ICF Core Sets of chronic musculoskeletal pain conditions, where the authors concluded that in people with CWMP, the profile of functioning differs considerably and should not be included in a common ICF Core Set with other musculoskeletal diseases.53
Pain Intensity
The use of self-reported pain as a variable was justified in a study by Walsh and Coggon54 that dealt with the reproducibility of histories of LBP. It is well known that a considerable portion of the general population frequently has LBP. In this respect, the participants of the pain-free group in our study did not represent accurately the general population, as the participants were selected because they stated they had not had any back problems for at least 3 months prior to entering this study.
High pain intensity, as reported by the patients with CLBP and WMP compared with the patients with only CLBP in this study, suggests that people reporting intense pain should be taken seriously. Significantly, pain intensity and the SF-36 physical component scale score correlated negatively in both groups (CLBP+WMP group: r=−.544, P<.000; CLBP-only group: r=−.518, P<.000). No significant correlation between the SF-36 mental component summary score and pain intensity for either group was calculated (CLBP+WMP group: r=−.067, P=.529; CLBP-only group: r=.049, P=.740).
In an FMS study, the authors concluded that the process of developing FMS starts with localized pain in most cases55 and that back pain could be a prognostic factor for the development of FMS.56 Ruiz Moral et al57 concluded in their study regarding psychosocial features of patients with CWMP and FMS in primary care settings that the patients’ self-rated health was poor and more closely resembled the health reported by patients with other chronic osteoarticular diseases. These results support the hypothesis that FMS should be considered as a more-advanced clinical stage of the WMP continuum.
Bergman et al58 observed that changes in SF-36 scores over a 3-year follow-up period coincided with improvement or deterioration of pain status in patients with chronic widespread pain compared with individuals from the general population with no chronic pain and with patients with chronic regional pain. These results, however, contrast with our results regarding pain intensity, which did not correlate significantly with the SF-36 mental component summary scores but did correlate with the SF-36 physical component summary scores in both the CLBP+WMP and CLBP-only groups.
Psychological Factors
Over the past 20 years, a multidimensional approach to the understanding of pain that incorporates a psychosocial model has gained acceptance. It currently rates psychological factors highly in pain research and treatment.59 Psychosocial variables generally have even more impact than biomedical or biomechanical factors on back pain disability.60
In our study, we observed that higher depression, anxiety, somatization, fear-avoidance behavior, and endurance capacity are factors associated with patients with WMP in comparison with individuals who are pain-free. These results concur with those of a previous study that demonstrated the importance of psychological variables as risk factors for back and neck pain.61
Depression
The cut point of the General Depression Scale for people to be considered clinically depressed was described to be greater than 23 points.23 In our study, 24.7% of the CLBP+WMP group but only 2.1% of the individuals of the pain-free control group had more than 23 points. When evaluating these results, one has to take into consideration that in the group with CLBP and WMP, women were more numerous than men and that lifetime prevalence of depression, in general, is higher in women than in men.62,63
However, the results for depression in our study correspond with the results reported in the literature. Fibromyalgia syndrome and depression commonly occur.64 Henningsen et al65 concluded that FMS is related to, but not dependent on, depression and anxiety. White et al66 described depression (and anxiety) as frequent and severe among patients with FMS. They found that affective disorders are risk factors for not only the development but also the continuum of FMS. Furthermore, depressed mood is a predictive factor for a negative treatment response in patients with FMS.67
Although it has been hypothesized that FMS is a depression spectrum disorder, it has been pointed out that not all patients with FMS develop major depression.68,69 Between 40% and 80% of patients with FMS in the study by White et al66 reported havign anxiety or depression, whereas anxiety stress and depression were found to be present in 30% to 45% of patients with WMP in a study by Yunus.70 Stratz et al71 discerned 3 different types of FMS: a biological type (inflammatory process), FMS as a result of depression-somatization, and a type of FMS as a result of a stress disorder or of maladaptive coping strategies.
As our pain clinic has an orthopedic focus, the referred individuals might have had a lesser psychopathological background, and the patients in this study were more likely to have the biological type of the syndrome, which might explain some differences between our findings and those of others. Thus, in our study, the SF-36 physical component summary score had a significant negative correlation with pain intensity, whereas the SF-36 mental component summary score did not.
Quality of Life (SF-36)
Comparing quality of life in patients with different musculoskeletal diseases, patients with FMS, despite their relatively young age, appear to be the group with the worst scores for quality of life.72 Similar results also were obtained in our study: the patients of the CLBP+WMP group had significantly lower scores on physical and mental aspects of the SF-36 health survey compared with the CLBP-only group and the pain-free control group. We found a greater difference between the CLBP+WMP and control groups for the physical component summary scores than for the mental component summary scores. This finding suggests that in the CLBP+WMP group, despite the significant group difference for both summary scores, the physical aspects were dominant compared with the mental aspects. Between the CLBP-only and control groups, a significant difference was found for the SF-36 physical component summary scores but not for the mental component summary scores. According to the study by Oswald et al,73 the SF-36 mental component summary score can be used to differentiate between patients with and without psychological dysfunction independent of pain. In our study, we found a significant negative correlation between BMI values and SF-36 physical component summary scores in the CLBP+WMP group (r=−.378, P<.000), whereas no significant correlation was found in the CLBP-only group (r=−.080, P=.440).
Fear-Avoidance Behavior
Fear-avoidance beliefs are particularly common in patients whose LBP is likely to become chronic.61 In the present study, fear-avoidance behavior was identified as an associated factor pertaining to patients with CLBP and WMP when compared not only with the individuals who were pain-free but also with the patients with CLBP only. The participants in the CLBP+WMP group reported an earlier onset of pain compared with the CLBP-only group. Based on these findings, it could be argued that fear-avoidance behavior plays an essential part in the development from CLBP alone to CLBP with WMP.74
Coping and Cognitive Reactions to Pain
Chronic low back pain and WMP are described to be particularly frequent in people with low coping abilities and high levels of helplessness and hopelessness,75 variables that in this study were found to be significantly more present in the patients with WMP than in the individuals who were pain-free. It seems obvious that the reduction of chronic pain is much more difficult if the pain problem is combined with other factors that are linked to different senses in the brain. This also explains why a biopsychosocial model, which implicates a multimodal perception and reaches many different senses, can enable such people to develop better coping strategies and reduce psychological strain. According to our results, patients with WMP prefer passive strategies as coping reactions to pain. This preference became understandable when considering that these patients very often have depression and, therefore, also a lack of drive.
In our study, a higher endurance capacity was found to be an important characteristic of the patients of the CLBP+WMP group compared with the individuals from the pain-free control group. Our results confirm previous findings in patients with FMS.76 These individuals frequently demand too much of themselves, neglect to recognize their own capacity limits, and are devoted to others’ needs.76,77 Sacrifices and a lack of self-concern follow suit.41
Balance/One-Leg Stand
We noted that balance (the one-leg-stand test) seemed to be an additional factor associated with the patients with CLBP and WMP compared with individuals who were pain-free. Requirements for a longer balance time are muscular strength (force-generating capacity), endurance, and coordinative abilities. The research literature suggests a reduced voluntary muscular strength in patients with FMS in comparison with individuals who are healthy.78,79 Strength training and aerobic endurance exercises can reduce pain and improve functionality, as shown in women with FMS.80,81 Gowans et al82 found that exercise can improve mood as well as physical function in individuals with FMS. Furthermore, another study83 concluded that regular high-intensity aerobic exercise alleviated pain disability and psychological strain in subjects with CLBP. The reported effects of aerobic walking on pain and disability in individuals with FMS were inconclusive.84 The complexity in the assessment of patients with chronic pain becomes obvious when considering that reduced muscular performance may be affected by an impaired central drive, a significant symptom of depression,78 and fear of increased pain after the test,85 all notable variables in this study.
Hypermobility
In this study, no statistically significant difference was noted on the Beighton Hypermobility Score in the CLBP+WMP group compared with the pain-free control group. These results differ from those of studies showing that patients with FMS had much higher Beighton Hypermobility Scores compared with subjects who were healthy.69,86,87 Karaaslan et al88 stated that WMP is associated with joint hypermobility under the age of 50 years.
Psychological Childhood Trauma and Health Care Seeking
In this study, the univariate analyses revealed significant differences between the CLBP+WMP and control groups with regard to a history of childhood psychological trauma and some current stress. Alexander et al89 observed in patients with FMS a connection between sexual or physical abuse and increased use of outpatient health care services, as well as medications for pain. Kadam et al90 noted that people who reported chronic widespread pain seek medical advice about nonmusculoskeletal problems more often than people with no pain, a finding that was not explained by psychological distress. This observation corresponds with the findings in our study, namely that the number of psychological stresses from earlier years and the number of comorbidities were significantly higher in the CLBP+WMP group than in the pain-free control group.
Limitations of the Study
With the opportunity to win a prize when participating in this study, the recruited individuals who were healthy could have been a self-selected and well-motivated group with a positive attitude toward the completion of the questionnaires. In order to evaluate such a large number of variables, an even larger number of study participants would be desirable. In addition, some variables in testing the patients with WMP and the individuals who were pain-free were not used with the patients with CLBP only.
Another possible limitation of this study might be recall errors by participants, especially regarding questions concerning their childhood. Additionally, all results of one assessment show no causative connections, but only associations. Therefore, further research is needed. Some scores have not been validated in patients with diffuse musculoskeletal pain or in adults who are healthy.
Conclusions
It is apparent that there are no simple explanations for patients with CLBP in combination with WMP when comparing them with patients with CLBP only and with individuals who are pain-free. It seems that only a large number of interacting physical and psychosocial factors, which were identified in this study, could classify the problems of these patients. Particularly, a high fear-avoidance behavior, disability, and a large number of treatments should alert clinicians to the potential early stage of WMP. Our results suggest opportunities for further research, with attention to a multidimensional view in the early stages of CLBP and WMP, the developmental time factor, and the well-timed management of the associated factors indicated in this study.
Footnotes
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Dr Friedrich provided concept/idea/research design and project management. Dr Friedrich and Dr Wepner provided writing. Ms Hahne provided data collection and analysis. All authors provided consultation (including review of manuscript before submission). The authors thank the patients who participated in this study and the Austrian Federal Ministry of Women and Health for supporting this study.
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The study was approved by the Internal Review Board of Orthopaedic Hospital Speising.
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↵* Performance Attainment Associates, PO Box 528, Lindstrom, MN 55045.
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↵† Pain Diagnostics and Thermography Inc, 233 East Shore Road, Great Neck, NY 11023.
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↵‡ StatSoft Inc, 2300 E 14th St, Tulsa, OK 74104.
- Received March 31, 2008.
- Accepted April 21, 2009.
- American Physical Therapy Association
References
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