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Keywords:

  • Pain;
  • Attention;
  • Fibromyalgia

Abstract

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. PATIENTS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. REFERENCES

Objectives

To investigate whether chronic pain patients have deficits in attentional functioning compared with pain-free controls, and whether fibromyalgia patients have larger deficits in attentional functioning compared with rheumatoid arthritis and musculoskeletal pain patients.

Methods

Sixty patients (20 in each of 3 patient groups) and 20 pain-free controls completed measures assessing pain intensity, mood, pain-related disability, somatic awareness, and catastrophic thinking about pain. Attentional functioning was assessed using an age-standardized, ecologically valid test battery. Analyses were made of between-group differences.

Results

Sixty percent of patients had at least one score in the clinical range of neuropsychological impairment, independent of demography and mood. Fibromyalgia patients were more anxious and somatically aware than rheumatoid arthritis or musculoskeletal pain patients, but did not show larger attentional deficits than other patient groups.

Conclusion

All 3 groups of chronic pain patients, regardless of diagnosis, had impaired cognitive functioning on an ecologically sensitive neuropsychological test of everyday attention.


INTRODUCTION

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. PATIENTS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. REFERENCES

It is a common clinical observation that chronic pain patients often report cognitive deficits including concentration and memory problems. Few studies have attempted to quantify the extent of cognitive deficits in chronic pain patients. Kewman et al (1) used a brief standardized computer screening test and found that approximately one-third of their pain patients had at least one index score in the impaired range. Grigsby et al (2) compared the performance of chronic pain patients with pain-free head injured patients on a variety of computerized tasks designed to assess speed of information processing and short-term memory. They found that the chronic pain patients performed poorly compared with the head injured patients on 33% of the speed of information processing tasks, and equally or worse than head injured patients on all other measures. Eccleston and Crombez (3) documented that patients with chronic pain who reported higher levels of both pain and somatic awareness showed significant performance decrements on an attentionally demanding switching task compared with other chronic pain patients.

Patients with fibromyalgia (FM) typically experience widespread musculoskeletal (MSK) pain, stiffness, and fatigue (4). These patients generally also report high levels of somatic awareness (5). Although data are scarce regarding cognitive deficits in FM patients, many of these patients report attention and memory deficits (6). Sletvold et al (7) investigated attention and memory deficits in FM patients and found only attentional deficits in FM patients compared with healthy controls on 2 standardized attention tests. In a well-designed study, Grace et al (8) reported that compared with matched healthy controls, FM patients showed significant attentional and memory deficits on a neuropsychological test battery. The attentional deficits were found between groups on the Paced Auditory Serial Additions Test (PASAT) but not on the attention/concentration index of the revised Wechsler Memory Scale. It is notable that these reported attentional deficits were observed only when task performance had a high attentional demand. Unfortunately, because both studies (7, 8) tested only FM patients and pain-free controls, it is not possible to conclude whether the reported deficits were primarily related to FM, or whether patients with FM experience greater attentional disruption in comparison with other chronic pain patients. There is some evidence to suggest that patients with a diagnosis of FM will demonstrate greater deficits due to a decreased tolerance to pain (and possibly to other stressors), a heightened attention to pain, and an increased interruptibility (6, 9, 10). However, no single study has compared these deficits in patients with different rheumatologic diagnoses.

This study examines attentional functioning between groups of chronic pain patients, using a standardized neuropsychological test with a high level of ecological validity. The study was designed to test 2 related hypotheses: 1) All chronic pain patients, regardless of diagnosis, will exhibit performance decrements on all measures of attention compared with pain-free controls, and 2) FM patients will show significantly greater impairment on attentional tasks compared with rheumatoid arthritis (RA) and musculoskeletal pain patients.

PATIENTS AND METHODS

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. PATIENTS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. REFERENCES

Patients.

Sixty patients were consecutively recruited over a 3-month period from inpatient and outpatient settings at a national hospital specializing in rheumatic diseases. Inpatient admission was for a variety of reasons, predominantly to gain access to specialized intensive assessment and therapy. All patients reported chronic persistent pain for at least 6 months and were able to easily perform the manual fine motor tasks required during neuropsychological testing. Patients were classified according to the primary diagnosis recorded in their medical chart. In all patients the diagnosis was made according to the American College of Rheumatology criteria (4) and was reassessed prior to their admittance into the study. Three diagnostic groups were formed: FM (n = 20), RA (n = 20), and MSK pain (n = 20). Twenty pain-free control participants were recruited and age-matched to the RA group who had the highest mean age, in order to control for age-related declines in attentional functioning (11). Age matching to the oldest group was considered the most conservative sampling technique to reduce the possibilities of Type 1 errors. The pain-free controls were recruited from the community and from among hospital volunteers and employees. The first 20 of these volunteers who met inclusionary criteria were tested. All participants spoke English as their primary language and had normal or corrected-to-normal vision and hearing. Exclusion criteria included a history of neurologic disorder, head injury, medical conditions known to affect cognitive functioning (e.g., lupus erythematosus), history of psychiatric illness, or learning disability. Biographic and clinical details are shown in Table 1.

Table 1. Demographic, pain, medication, sleep and psychological status of patients with chronic pain associated with rheumatoid arthritis, fibromyalgia, musculoskeletal disorders, and pain-free control groups*
 Rheumatoid arthritis group (n = 20)Fibromyalgia group (n = 20)Musculoskeletal disorders group (n = 20)Pain-free controls (n = 20)
  • *

    Except where indicated, values are the mean ± SD. VAS = visual analog scale; NSAIDs = nonsteroidal antiinflammatory drugs; HAD = Hospital Anxiety and Depression Scale; PDI = Pain Disability Index; MSPQ = Modified Somatic Perceptions Questionnaire; PCS = Pain Catastrophizing Scale.

  • Significantly different compared with control group (P < 0.005).

  • Significantly different compared with control group (P < 0.005), and rheumatoid arthritis and musculoskeletal disorders group (P < 0.005).

Demographic data    
 Age, years62.9 ± 10.948.0 ± 16.952.3 ± 13.160.0 ± 12.4
 Sex, f/m16/418/212/87/13
 Years of education12.5 ± 2.713.1 ± 3.412.7 ± 3.914.3 ± 3.7
 Inpatient, %757075NA
Current pain intensity    
 VAS score, range 1–104.5 ± 2.54.6 ± 1.84.7 ± 2.20.2 ± 0.3
Pain chronicity    
 Years in pain18.9 ± 15.311.0 ± 8.610.2 ± 12.20.0 ± 0.0
Involved site of pain    
 Joints, %40105NA
 Back, %0010NA
 Limbs, %5020NA
 All over, %407525NA
 Other, %151540NA
Taking medication    
 Opioids, %6060300
 Non-opioid analgesics, %4020200
 NSAIDs, %5025450
 Other, %8070750
Sleep status    
 Sleep per night, hours6.5 ± 1.75.9 ± 2.66.2 ± 2.06.3 ± 1.9
 Wakings per night2.4 ± 1.53.6 ± 1.62.3 ± 1.91.4 ± 1.4
Psychological status    
 HAD-Depression, range 0–215.5 ± 3.27.9 ± 5.17.1 ± 4.51.9 ± 3.5
 HAD-Anxiety, range 0–215.7 ± 3.710.6 ± 4.88.2 ± 4.34.8 ± 2.5
 PDI, range 0–706.0 ± 2.26.0 ± 1.95.5 ± 2.40.6 ± 1.1
 MSPQ, range 0–187.7 ± 6.013.3 ± 4.79.3 ± 6.21.5 ± 3.1
 PCS, range 0–5216.2 ± 11.924.3 ± 14.720.1 ± 14.26.4 ± 5.2

Neuropsychological testing.

Attentional functioning was assessed using the Test of Everyday Attention (TEA) (12), which provides an overall score, as well as summary scores of cognitive performance in 4 domains of cognitive functioning: selective attention, sustained attention, attention switching, and auditory-verbal working memory. The TEA is a reliable and robust tool that provides individual age-controlled normative data for comparison. It has strong ecological and face validity. Completion rates are good due to the short (45–60 minutes) testing time.

Self-report measures.

In addition to the biographic and clinical details, 5 psychological inventories were also administered: 1) Pain intensity ratings were measured with a 10-cm visual analog scale (VAS) anchored at each end with the phrases “no pain” and “worst pain imaginable” at the time of testing. 2) Depression and anxiety were measured with the Hospital Anxiety and Depression Scale (13). This brief (14-item) measure is structured in a manner pertinent to a hospital environment. A typical depression item is “I feel cheerful,” and a typical anxiety item is “I get sudden feelings of panic.” 3) Disability in everyday functioning due to pain was measured with the Pain Disability Index (PDI) (14). The PDI measures perceptions of disability in 7 areas of everyday life (e.g., family/home responsibilities and social activity). Patients agree or disagree with statements using a 0–10 Likert scale anchored at each end by the phrases “no disability” and “total disability.” 4). Somatic awareness was measured with the Modified Somatic Perception Questionnaire (15). This instrument was designed specifically for use with chronic pain populations and measures the frequency and range of sensations in a list of 22 body sensations (e.g., stomach churning or increased heart rate). 5) Catastrophic thinking about pain was measured with the Pain Catastrophizing Scale (16). This is a 13-item scale developed for use in both nonclinical and clinical populations. Patients reflect on past painful experiences and indicate the degree to which they experienced thoughts or feelings during pain on a 5-point scale (e.g., “I can't seem to keep it out of my mind,” and “I feel I can't stand it any more”).

RESULTS

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. PATIENTS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. REFERENCES

Descriptive statistics of the self-report measures are reported in Table 1. Group differences on all descriptive measures were tested using pairwise comparisons with Bonferroni corrections to control for multiple testing. Compared with the pain-free control group, the 3 patient groups had significantly more pain, depression, pain-related disability, higher levels of somatic awareness, and catastrophic thinking about pain. FM patients were significantly younger and reported more anxiety than all other groups. They also reported a significantly higher level of somatic awareness than the RA patients. There were no differences between inpatients and outpatients on any of the measures.

Correlational analyses were performed with demographic measures, self-report measures, and TEA scores. Patients' self-report measures of pain at the time of neuropsychological testing, depression, anxiety, pain disability, somatic awareness, pain catastrophizing, and sleep (number of hours of sleep and number of wakings per night) tended to be significantly correlated (see Table 2). However, none of these variables were significantly correlated with any of the TEA index results.

Table 2. Two-tailed Pearson's correlation between self-report measures for all patients*
VariablePain VASHrs sleepSleep disruptHAD-AnxHAD-DepPDIMSPQPCS
  • *

    Pain VAS = pain intensity at time of testing on visual analog scale; Hrs sleep = average number of hours sleep per night; Sleep disrupt = number of wakings per night's sleep; HAD-Anx = Hospital Anxiety and Depression Scale anxiety score; HAD-Dep = HAD depression score; NS = not statistically significant at P < 0.05. See Table 1 for additional definitions.

  • P < 0.05.

  • P < 0.01.

  • §

    P < 0.001.

Pain VASNSNS0.340.380.53§0.45§0.47§
Hrs sleep NSNSNSNS−0.27−0.32
Sleep disrupt  NS0.300.360.390.46§
HAD-Anx   0.63§0.330.400.70§
HAD-Dep    0.52§0.320.62§
PDI     0.48§0.56§
MSPQ      0.48§

A series of analyses of variance were performed to examine group differences in performance on the overall TEA, and on the summary scores for the subscales of selective attention, sustained attention, auditory-verbal working memory, and attentional switching. Specific group differences were tested using pairwise comparisons with Bonferroni corrections to control for multiple testing. The means and standard deviations of the overall TEA and the domains of cognitive functioning are included in Table 3. All TEA score results are derived using the TEA's individual age-normed scaled scores. All significant between-group differences in attentional functioning remained significant when age, depression, anxiety, somatic awareness, and catastrophizing were included as covariates. Scores from patients who received opioid medication did not differ significantly from the scores of patients who did not receive opioids on any of the TEA measures.

Table 3. Results of overall performance and subtest scaled scores on the Test of Everyday Attention (TEA) for patients with chronic pain associated with rheumatoid arthritis, fibromyalgia, musculoskeletal disorders, and pain-free control participants*
 Rheumatoid arthritis groupFibromyalgia groupMusculoskeletal disorders groupPain-free control group
  • *

    Values are the mean ± SD.

  • Compared with control group, P < 0.005.

  • Composite scores that were derived from the sum of scaled scores of subtests for the selective attention, sustained attention, and working memory indices.

Overall TEA score (mean of all standard scores)8.0 ± 1.18.7 ± 1.68.6 ± 2.010.5 ± 1.4
Selective attention24.8 ± 6.125.2 ± 6.625.1 ± 10.133.4 ± 8.0
Sustained attention23.8 ± 4.627.4 ± 3.525.6 ± 5.929.3 ± 3.7
Attention switching7.4 ± 3.59.2 ± 3.67.6 ± 2.99.5 ± 3.1
Working memory15.0 ± 4.417.9 ± 5.518.5 ± 4.022.2 ± 4.4

Overall TEA score.

There was a significant effect for group on mean TEA standard scores (F[3,76] = 9.87, P < 0.0001). Pairwise comparisons revealed that pain-free controls performed better than each of the 3 patient groups. The FM group had the same performance as the other patient groups. No other differences were significant.

Selective attention.

There was a significant effect for group on the composite score (sum of scaled scores of subtests for this index) of selective attention (F[3,74] = 5.42, P < 0.003). Pairwise comparisons revealed that pain-free controls had a significantly higher level of performance than each of the patient groups. The FM group did not perform worse than the other patient groups. No other between-group differences were observed.

Sustained attention.

There was a significant effect for group on the composite score (sum of scaled scores of subtests for this index) of sustained attention (F[3,73] = 5.43, P < 0.003). Pain-free controls were more able to sustain attention than patients in the RA group. There was no significant difference between the pain-free controls and the other two patient groups. FM patients did not perform worse on sustained attention than the 2 other patient groups. No other between-group differences were observed.

Attention switching.

No between-group differences were observed on the summary score related to attention switching (F[3,73] = 2.01, P not significant).

Working memory.

There was a significant main effect for group on a composite score (sum of scaled scores of subtests for this index) of auditory-verbal working memory (F[3,72] = 8.13, P < 0.0001). Pain-free controls had higher scores than the FM and RA patients, but they were not significantly different from the MSK patients. No other between-group differences were observed.

A further analysis showed that 60% of patients had at least one TEA subtest score in the clinically impaired range compared with 20% of healthy controls. Further, 38% of patients and only one (5%) of the healthy control participants had more than one subtest score in the impaired range.

DISCUSSION

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. PATIENTS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. REFERENCES

In this study a majority of patients with chronic pain exhibited cognitive problems. Sixty percent of the patients had at least one score in the “clinically impaired” range (scaled score ≤ 5) compared with 20% of the pain-free controls. This suggests that although at the group level mean TEA score differences would place chronic pain patients in a mildly impaired range in terms of attentional functioning (see Table 3 for group means), at the individual level, the majority of chronic pain patients showed severe impairment on at least one attentional index. Attentional deficits in the patient groups were significant on tasks of selective and sustained attention, and auditory-verbal working memory. These results further document the extent of concentration and memory problems of chronic pain patients. Because these deficits are found with a test battery specifically designed to be ecologically valid, it is reasonable to expect that the observed deficits are clinically relevant for everyday cognitive functioning.

It may be interesting to note that although expected correlations existed between a number of the mood and pain-related self-report measures, there was no correlation between attentional functioning and any of these factors. This is in partial contrast to the findings of Grace et al (8), in which their patients diagnosed with FM showed modest correlations between trait anxiety and performance, and pain severity and performance on the PASAT.

The finding that TEA results were not correlated to the pain VAS measures suggests that attentional disruption may not be related to the level of pain experienced at a given time. It may be that the observed attentional disruption in chronic pain patients was less a result of the pain they were experiencing during testing and more a result of having a history of chronic attentional disruption by pain, as discussed by Eccleston and Crombez (3). Another objective of this study was to investigate whether FM is characterized by more severe cognitive problems, or by a specific attentional problem. Although FM patients showed a significantly higher level of anxiety than the other 3 groups, this study did not reveal that FM patients had more severe attentional problems than other chronic pain patients. Furthermore, FM patients did not show poorer performance than patients with RA or MSK in any of the investigated domains of attentional and cognitive functioning. These results are the first to show that patterns of attentional performance are comparable among chronic pain patients with different rheumatologic disorders. They suggest that the observed attentional deficits may be related more to the presence of chronic pain than to any specific disease-related factor. There are a number of issues that could be improved upon in future studies. First, further studies could explore the possible mediating role of psychological and medical variables in producing attentional deficits of this order. A larger patient sample will allow regression modeling and an exploration of the potential mediating role of specific psychological variables (3).

Second, due to the considerable variability in types and doses of medications taken, it was not possible to fully control for the putative effects of medication. The RA and FM groups reported greater use of opioid medications compared with the MSK group. However, although a variety of medications, including opioids, are known to affect cognitive function, recent data have shown that attentional functioning is either not disrupted or improves in individuals, including chronic pain patients, following opioid consumption using both performance and electrophysiological measures (17–22). In our study, patients who received opioid medications did not perform significantly differently from patients who did not receive opioids.

Third, in this study the pain-free control group contains a majority of male participants, although the patient groups contain a majority of females. This difference arose due to our use of a pragmatic consecutive sample design for both the patient and pain-free groups. Although the TEA is gender neutral and not normed on the basis of sex, a future study could ideally use a sampling technique that matches both age and sex across samples.

Finally, these findings could be strengthened in future work with the addition of self-report measures of perceived performance, cognitive effort, and test anxiety. More specific measures of the attentional presentation of patients may also help to clarify the source of the pain-related decrement in performance (23). The addition of a computerized version of this test battery will allow for the micro-analysis of specific attention and memory functions.

This study supports previous findings by reporting that many chronic pain patients have significant attentional dysfunction. An important, novel finding is that regardless of disease status, chronic pain patients demonstrate cognitive impairment when performing everyday attentional tasks when compared with matched pain-free controls. Further investigation and clarification are warranted to more fully understand the nature of these attentional deficits, their underlying mechanisms, and their clinical implications.

REFERENCES

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. PATIENTS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. REFERENCES
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