| | Cognitive Complaints Are Associated With Depression, Fatigue, Female Sex, and Pain Catastrophizing in Patients With Chronic PainPresented in part to the American Pain Society, October 21–24, 1999, Ft. Lauderdale, FL. Abstract Roth RS, Geisser ME, Theisen-Goodvich M, Dixon PJ. Cognitive complaints are associated with depression, fatigue, female sex, and pain catastrophizing in patients with chronic pain. Arch Phys Med Rehabil 2005;86:1147–54. ObjectiveTo examine the relation between demographic, pain-related, psychosocial, affective, and treatment factors and complaints of cognitive dysfunction among patients with chronic pain. DesignCross-sectional survey. SettingA university hospital outpatient multidisciplinary chronic pain program. ParticipantsChronic pain patients (N=222; 135 women, 87 men) completed a battery of psychometric questionnaires as part of an initial evaluation on referral to the program. InterventionsNot applicable. Main Outcome MeasuresCognitive impairment was assessed with items from the Brief Symptom Inventory; measures of depressive symptoms, pain intensity, posttraumatic stress disorder (PTSD), and pain catastrophizing were obtained from the Beck Depression Inventory (negative affect, negative self, somatic/physical function), McGill Pain Questionnaire, Modified Posttraumatic Chronic Pain Test, and Coping Strategies Questionnaire, respectively; and measures of subjective sleep disturbance, fatigue, opiate use, compensation/litigation status, pain location, and relevant demographic data were obtained from an open-ended questionnaire. ResultsCorrelational analysis indicated that female sex, pain intensity, PTSD symptoms, depressive symptoms, catastrophizing, pain location (neck), and fatigue were all positively related to cognitive complaints. Simultaneous regression analysis showed that all factors combined accounted for 52% of the variance in self-report of cognitive difficulties and that 6 variables had a significant unique contribution to the report of cognitive complaints in the following order of importance: depression-negative affect (β=.28, P<.05), fatigue (β=.17, P<.05), depression-somatic/physical function (β=.16, P<.05), depression-negative self (β=.14, P=.05), pain catastrophizing (β=.12, P=.08), and female sex (β=.12, P<.05). ConclusionsComplaints of cognitive impairment among chronic pain patients appear to be associated with multiple factors, with particular attention to depressive symptoms, fatigue, and catastrophizing. Our results also suggest that women with chronic pain are particularly vulnerable to cognitive dysfunction.
CHRONIC PAIN PATIENTS without a history of head trauma frequently complain of cognitive deficits such as memory loss and concentration difficulties. 1, 2, 3 Even among pain patients with traumatic brain injury (TBI), pain intensity is inversely related to performance on neuropsychologic testing. 4, 5 Recent neuropsychologic reports document problems with immediate and delayed memory, 6, 7 long-term memory with effortful processing, 8 and verbal fluency 9 among chronic pain patients, although not all studies have found cognitive deficits for this population. 10, 11 In a comprehensive review of studies that examine the effect of chronic pain on neuropsychologic functioning in people without a history of TBI, Hart et al 12 concluded that there is consistent evidence for disturbances in attentional capacity, processing speed, and psychomotor speed for these patients. Hart noted, however, that little is known about the variables that underlie the inverse relation between pain and cognitive function.
There is little consensus on how persistent pain brings about the observed decrement in cognitive function reported in these studies, and investigation into this relationship has been constrained by the absence of a conceptual model to guide hypothesis testing and experimental inquiry. Early studies by Radanov et al 13, 14, 15, 16, 17, 18 drew attention to the role of cervical injury, primarily among pain patients with a history of whiplash injury without head trauma, and its relation to cognitive dysfunction. These studies identified a consistent association between impaired cognitive performance on selected neuropsychologic tasks and a history of whiplash trauma. 15 Moreover, cognitive impairment was found to be positively related to psychologic distress. 13, 17 In 1 study, Radanov 14 compared whiplash patients who had sustained upper versus lower cervical trauma. Only the “upper cervical syndrome” subjects, of whom nearly half had sustained some degree of loss of consciousness at the time of injury, demonstrated impaired performance on the cognitive tasks administered. These results suggested a possible role for subtle brain injury in explaining the cognitive deficits observed among patients with whiplash trauma. However, in a later review Radanov 15 concluded that the cognitive deficits commonly associated with whiplash-related pain appear to be attributable to persistent pain and its associated affective distress rather than to brain injury. Consistent with this assessment was evidence that the majority of pain-related cognitive problems resolve in parallel with resolution of the pain symptoms. 15 Although these studies highlighted the prevalence of cognitive complaints among this single group of chronic pain patients, it is clear that pain patients without whiplash injury report cognitive dysfunction with considerable frequency 12 and that an adequate conceptual model for understanding pain-induced cognitive disturbance must account for cognitive deficits unrelated to speculations of direct brain insult.
Recently, several writers have invoked the role of disturbed attentional processes to explain the adverse impact of chronic pain on cognitive function. Lorenz and Bromm 19 suggest that pain may interfere with “attentional resources” that are necessary for the performance of concurrent cognitive tasks. In the most elaborate model on the relation between pain and attention thus far proposed, Eccleston and Crombez 20 present a cognitive-affective model that highlights the interruptive effect of a pain stimulus on the directed control of attention. In their model, the researchers emphasize the superordinate biologic function of pain as a signal to the organism of impending harm or threat, thereby activating motivational systems to promote behavioral action, most typically in the form of escape. In their view, the primacy of information conveyed by a strong pain stimulus compels a disruption in ongoing attentional processes, leading unequivocally to the redirection of attentional resources to the (potentially) aversive stimulus. The resultant interruption of attentional focus thus compromises cognitive performance for tasks that involve more complex information processing and integration. The model emphasizes the potential influence of pain-related variables such as pain intensity and the threat value of the pain stimulus as potential moderators of the effect of a pain stimulus on cognitive function. Empirical findings consistent with this model include evidence that, for a chronic pain population, pain intensity predicts greater cognitive impairment 3, 21, 22, 23 and pain-related fear is positively related to more severe cognitive impairment. 24
Examining the pathway by which pain influences cognitive functioning is hampered by the myriad of variables, beyond the pain experience itself, that are associated with chronic pain and that can potentially affect cognitive processes. Chronic pain is commonly associated with both a number of comorbidities and treatment factors that can adversely affect cognitive function. For example, chronic pain patients have a high incidence of affective distress, depression, and anxiety, 25, 26, 27 all of which are known risk factors for cognitive disturbance among pain patients. 1, 3, 7, 8, 24, 28, 29 Chronic pain patients frequently present with disturbed sleep and excessive fatigue, each of which correlates with cognitive impairment. 24, 29, 30, 31 Pain patients are frequently observed to exhibit high somatic focus, and there is evidence that intense bodily preoccupation (eg, somatization) is associated with disturbances in attention, verbal memory, and visuospatial processing. 23, 32 The onset of a chronic pain problem is often associated with a traumatic injury or accident. 33 In this regard, Goldberg et al 30 found that patients with the onset of temporomandibular dysfunction (TMD) pain after a whiplash injury, compared with a group whose TMD pain disorder was idiopathic in origin, performed with more severe impairment for measures of short-term memory, simple and choice reaction time, and verbal learning. These findings suggest that the traumatic onset of pain may have a particular relation to cognitive impairment for patients with chronic pain.
It follows, then, that 1 limitation of previous studies examining cognitive function among chronic pain patients has been the failure to examine simultaneously the host of variables that are associated with or have the potential to interfere with cognitive function. As a result, these studies have limited ability to identify those factors that may account for the observed deficits in cognitive function and to determine which variables are most strongly related to cognitive disturbance. Moreover, several of these variables are naturally correlated in a chronic pain population and may share common variance in explaining cognitive disturbance among these patients. Studies that investigate factors contributing to cognitive complaints among chronic pain patients should measure and analyze a large number of relevant correlates, and simultaneous regression analyses should be done to determine the unique contribution of each predictor to the observed variability in cognitive function. A recent study 24 that used this approach is instructive.
McCracken and Iverson 24 assessed self-reported cognitive complaints of consecutive chronic pain patients attending a university pain clinic. They examined an array of potentially significant correlates of cognitive dysfunction among their subjects, including relevant demographic variables, litigation status, pain severity, pain location, pain-related anxiety, depressive symptoms, sleep quality, and medication usage. Over half of the patients complained of at least 1 cognitive problem. Frequent complaints included memory impairment, minor accidents, difficulty completing tasks, and attentional deficits. Correlational analysis indicated that cognitive complaints held a significant but low association with low educational achievement, male sex, narcotic medication usage, and sleep disturbance. Moderate correlations were obtained between reported cognitive complaints and antidepressant use, pain severity, pain-related anxiety, and depression. A subsequent multiple regression analysis showed that only depressive symptoms, the use of antidepressants, and pain-related anxiety had significant association with cognitive complaints, when examining all factors simultaneously.
The present study examined the contribution of a broad set of variables that have shown an association with, or have the potential to affect, cognitive functioning for a heterogeneous group of chronic pain patients. We used a simultaneous regression model to ascertain the variables that are most strongly and uniquely related to cognitive complaints for this population. The study attempted to replicate the results of McCracken and Iverson and also included independent variables (eg, posttraumatic stress disorder [PTSD], fatigue) not contained in their study that have reasonable likelihood of sharing a significant relation with cognitive complaints. We also analyzed separately the 3 dimensions of depression from the Beck Depression Inventory (BDI) described by Morley et al 34 to determine which aspects of depression are most highly associated with cognitive complaints. Considering the available data and theoretical models, 20 we hypothesized that cognitive complaints would be most closely related to mood disturbance, pain severity, and excessive preoccupations with the pain stimulus (eg, catastrophizing).
Methods  Participants Subjects were 222 patients with chronic pain (defined as continuous pain for ≥3mo) referred to the Pain Management Program in the Department of Physical Medicine and Rehabilitation at the University of Michigan Health System. The total sample comprised 135 women and 87 men. The mean age ± standard deviation (SD) was 39.8±9.6 years, and the mean duration of the presenting pain complaint was 43.5±54.6 months. Pain locations were heterogeneous, with 42% of the sample presenting a primary complaint of low back pain, 22% reporting their pain was in 3 or more sites, 20% complaining of cervical pain, and 16% of subjects reporting a diverse array of pain symptoms. In terms of race, 197 (89%) were white, 17 (8%) were African American, 2 (1%) were Asian American, and 6 (3%) were of other ethnic origins. Examination of marital status indicated that 60% were married, 12% were single, 20% were divorced, and 3% were separated; 1 subject was widowed, and 3% indicated they were living with a significant other. Educational achievement was distributed as follows: 12% of the sample did not complete high school, 22% completed high school, 45% reported taking some college technical school courses, 11% completed college, and 10% had completed a graduate or professional degree. Eighty-five subjects (38%) were involved in some type of pain-related litigation, and 142 (64%) were receiving compensation for their pain symptoms. One hundred five subjects (47%) were taking either occasional or routine narcotic analgesics. The measures reported in this study were obtained from instruments administered as part of the patient’s clinical evaluation on referral to the program. Measures As part of the initial clinical evaluation for consideration for admission to the program, each subject completed a battery of psychometric inventories assessing pain, mood, coping strategies, and relevant demographic variables. Cognitive complaints To assess complaints of cognitive impairment, we drew 5 items from the Brief Symptom Inventory (BSI), 35 a 53-item self-administered questionnaire that measures 9 dimensions of psychologic functioning. In it, subjects are asked to rate the frequency with which individual items occurred during the past week on a 5-point scale of distress from “not at all” (0) to “extremely” (4). Higher scores indicate more severe psychologic impairment. The items relevant to cognitive difficulties and included in the analysis were as follows: (1) trouble remembering things, (2) having to check and double check what you do, (3) your mind going blank, (4) trouble concentrating, and (5) difficulty making decisions. Studies of the BSI have documented its psychometric integrity. 35 In the present sample, the internal consistency of these items (Cronbach α) was .89. Cognitive items from the Symptom Checklist 90-Revised, 36 of which the BSI is a shortened version, have been used previously to identify cognitive complaints among chronic pain patients. 28 Pain intensity The McGill Pain Questionnaire (MPQ) 37 was administered to assess pain experience. The MPQ evaluates the subjective experience of pain and quantifies it separately into sensory, affective, and evaluative dimensions. The MPQ yields a separate pain rating index (PRI) for sensory, affective, evaluative, and total pain experience. Factor analytic studies of the MPQ 38, 39 have shown high intercorrelations among the MPQ indices, raising questions regarding the discriminative capacity of the individual subscales and leading Turk et al 39 to recommend that the total PRI be used in studies of pain experience. Thus, for this study the MPQ total PRI was used as a measure of overall pain intensity. Repeat administration of the MPQ has yielded a 70.3% rate of consistency for the total PRI score. 37 The MPQ is frequently used in studies assessing pain intensity and experience. 40 Depressive symptoms Depressive symptoms were obtained from the BDI. 41 The BDI provides a measure of depressive symptoms and consists of 21 groups of items that assess both cognitive/affective and vegetative signs of depression. Alpha coefficients for the BDI in psychiatric and nonpsychiatric patients range from .73 to .95. 42 A large confirmatory factor analysis of the BDI 34 in a chronic pain population suggests that the measure consists of 2 factors: (1) items that reflect a negative view of the self and (2) items that assess physical function. A third group of items did not consistently load on any factor but reflected negative affect. Thus, negative self, physical function, and negative affect subscales were computed by summing the appropriate items. Posttraumatic stress To assess symptoms of pain-related posttraumatic stress, subjects completed a modified version of the Posttraumatic Chronic Pain Test (PCPT). 43 The PCPT consists of 6 items that assess the presence or absence of symptoms of PTSD related to an accident or injury that coincides with the onset of the patient’s primary pain complaint. The PCPT includes the following items: (1) “I feel upset or nervous when exposed to events that remind me of the original accident or injury that caused my pain”; (2) “Since the injury, I find myself avoiding places or activities that remind me of the accident or injury”; (3) “I have recurrent and intrusive memories of the events surrounding my accident or injury”; (4) “I have experienced recurrent dreams about the event surrounding my accident or injury”; (5) “Since the accident or injury I have become ‘wound up’ and startle easily”; and (6) “At times, I have suddenly felt or acted as if the accident or injury were actually happening again.” The scale was modified from the original true-false response format into a format in which patients were asked to rate the frequency of PTSD symptoms on a Likert scale ranging from “not at all” (0) to “very much” (6). Reliability data on the original instrument suggest that it has good test-retest reliability (.90); split-half reliability is reported to be .59, and interrater reliability is .93. 43 Reliability data for the modified version of the PCPT indicate that the scale has good internal consistency as measured by the Cronbach α (.86) and split-half reliability (.81) using the Spearman-Brown method. 33 Pain catastrophizing Catastrophizing was assessed by means of the catastrophizing subscale of the Coping Strategies Questionnaire (CSQ). 44 In it, participants rate on a 7-point scale how often they use each of 6 strategies to cope with pain. Reliability for this subscale is reported to be .78. 44 Catastrophizing has been consistently and strongly associated with several pain-related variables, including increased pain severity, greater pain disability, higher levels of affective disturbance, and less optimal pain treatment outcome. 45 Pain questionnaire Finally, subjects completed a comprehensive questionnaire that assessed demographic information, relevant pain variables (eg, duration, location) and treatment history, and compensation/litigation status. Categoric variables were coded as follows: educational level (1, did not complete high school; 2, completed high school; 3, some college or technical school training; 4, completed college; 5, completed a graduate degree or professional school program), opioid use (dummy coded as 0 for none, 1 for taking an opioid), sex (0, male; 1, female), litigation status (0, no; 1, yes), presence of neck pain (0, no; 1, yes), and compensation status (0, no; 1, yes). Likert ratings of daily fatigue were also obtained on this questionnaire, ranging from 0 (not tired at all) to 6 (extremely tired). Results Prevalence of Cognitive Complaints For the items assessing cognitive complaints, the means, SDs, frequency count, and percentage of responses to each question are in table 1. Overall, 62% of the patients complained of moderate to severe problems with at least 1 cognitive measure. Twenty-eight percent of the patients reported moderate to severe problems for all 5 cognitive complaint items of the BSI. The most commonly noted problem was “trouble concentrating” (75.2%). Correlational Analysis Pearson correlations of the variables examined in the regression analyses are in table 2. Female sex (r=.20); pain (r=.19); scores on the modified PCPT (r=.40); the BDI subscales of negative self (r=.54), physical function (r=.60), and negative affect (r=.63); the CSQ catastrophizing subscale (r=.46); fatigue (r=.37); and presence of neck pain (r=.13) all associated significantly with the sum of the 5 cognitive complaint items. Because many of these measures also share variance, as can be seen from the table, a simultaneous regression analysis was conducted to examine unique contributions to the prediction of cognitive complaints. Simultaneous Regression Analysis The simultaneous regression analysis was performed using the sum of the 5 BSI cognitive dysfunction items as the dependent variable. Multicolinearity in the regression analysis was controlled for by setting the minimum tolerance for entry for a particular variable at .01. Independent variables that were examined included age, sex, level of education, opioid use, presence of neck pain, pain duration, PCPT total score, BDI factors scores (less item 13), pain intensity (total PRI) from the MPQ, scores on the catastrophizing subscale of the CSQ, daily fatigue, litigation, and compensation status. All the items passed the minimum tolerance criteria. The results of the simultaneous regression analysis are in table 3. The independent measures together significantly predicted cognitive complaints as measured by the 5 BSI items (R=.72, F14,207=16.3, P<.001), and combined they accounted for 52.5% of the variance in cognitive complaints. Inspection of the independent contribution of each variable to the prediction of cognitive complaints, controlling for the other variables in the equation, indicated that 4 contributed significantly to the report of cognitive complaints and 2 contributed marginally. Negative affect as assessed by the BDI made the greatest contribution (β=.28, P<.05), according to the standardized regression coefficient. Self-report of fatigue made the next highest contribution (β=.17, P<.05), followed by BDI physical functioning (β=.16, P<.05) and BDI negative self (β=.14, P=.05). Sex was also significantly related to cognitive complaints, with women tending to report more complaints than men (β=.12, P<.05). Further, the CSQ catastrophizing subscale marginally correlated with cognitive complaints (β=.12, P=.08). |
⁎
P=.05.
†
P=.05.
‡
P<.08. |
Discussion Sixty-two percent of our sample reported moderately severe problems with at least 1 cognitive function, and 28% reported moderately severe problems with all 5 cognitive functions. Our prevalence rate for the report of at least 1 cognitive complaint is similar to Dick et al, 46 who found that 60% of a cross-section of chronic pain patients demonstrated at least 1 area of cognitive impairment on a battery of attentional tasks. These data are comparable to those reported by McCracken and Iverson 24 and Jamison et al, 28 who found that 42% and 55%, respectively, of their chronic pain subjects reported at least 1 significant area of cognitive deficit. Collectively, these findings provide consistent evidence for the relatively high frequency of cognitive complaints among people with chronic pain. Our multiple regression analysis further replicated several of the main findings of McCracken and Iverson. 24 Both studies found that symptoms of depression made the strongest unique contribution to complaints of cognitive deficits, with our results clarifying that all aspects of depression, as measured by the BDI, were significantly associated with reports of cognitive impairment. Both studies also found that a cognitive style associated with pain-related anxiety or worry (eg, catastrophizing in the present study) have significant and independent associations with cognitive complaints. Our findings differ from the McCracken and Iverson study: we found that fatigue and female sex made a significant contribution to the occurrence of cognitive complaints. Of interest, both studies found a moderate correlation between cognitive complaints and pain intensity for the correlational analysis, but this factor did not maintain a significant relation to cognitive function after the respective multiple regression analyses. Also of note, both studies failed to identify any association between cognitive complaints and age, pain duration, and litigation/compensation status. The evidence for the primary role of depression in explaining cognitive problems among chronic pain patients is not surprising. Convincing empirical evidence exists for a strong association between depression and cognitive impairment. 47, 48 In a meta-analysis of relevant studies published since 1975, Veiel 47 reviewed the evidence for neuropsychologic deficits among depressed patients and found empirical evidence for global diffuse impairment of neurocognitive test performance for this population, noting particular disturbances with frontal lobe function. Approximately 50% of depressed patients score in the severe impairment range for tests of neuropsychologic function. 47 There is general agreement that depression is the most common comorbid psychologic problem associated with chronic pain. 26 This knowledge plus our data suggest that the presence of depressive symptoms, particularly negative affect, is a primary source of cognitive disturbance for chronic pain patients. The role of depressive symptoms is readily illustrated by a series of studies assessing cognitive dysfunction among patients with fibromyalgia, a chronic pain syndrome of diffuse myalgias and arthralgias. Previous studies have documented that these patients have consistent problems with immediate and delayed memory, attentional information processing, and psychomotor speed when compared with various control groups. 6, 9, 29, 49 In a study of particular relevance to the present discussion, Landrø et al 8 assessed memory function in patients with either fibromyalgia or major depression and compared them with healthy volunteers. Both the fibromyalgia and the depressed subjects’ scores indicated significant impairment relative to controls for neuropsychologic tasks assessing long-term memory. When fibromyalgia patients with a lifetime history of depression were excluded from the analysis, no differences in memory emerged for the remaining fibromyalgia patients when compared with controls. In a related study, Suhr 31 noted that fibromyalgia patients report more severe cognitive impairment when compared with other chronic pain patients and healthy controls, but the groups do not differ in their performance on neuropsychologic testing. Further, Suhr found that depression and fatigue were significantly associated with cognitive complaints for memory and psychomotor function, respectively. These data suggest that depression may account for the deficits in cognition observed for fibromyalgia patients in previous studies. Taken together, the evidence is persuasive that depression is a potent predictor of cognitive problems among chronic pain patients and may provide the strongest explanatory power in understanding these complaints for this population. Our analysis also identified an important role for self-reported fatigue in explaining the cognitive complaints reported by our sample. Previous pain studies have observed a significant association between fatigue and impaired performance on neuropsychologic testing. 16, 29, 30 Indirect evidence for a relation between fatigue and cognitive disturbance among chronic pain patients draws from pain studies that have reported a positive association between sleep quality and cognitive function. 24, 29 Similarly, there is evidence that patients who suffer with chronic fatigue syndrome also complain of significant cognitive impairment. 50, 51 Cote and Moldofsky 29 suggested that fatigue associated with disturbed sleep may be the primary reason for the cognitive dysfunction observed in fibromyalgia patients. Suhr 31 reported a significant correlation for fibromyalgia patients between neuropsychologic deficits on psychomotor testing and fatigue. Our multiple regression analysis found empirical support for a unique and statistically significant contribution of fatigue, independent of its relation to depression, to cognitive complaints reported by our chronic pain patients. These data lend support for the further investigation of the relation between fatigue and cognition in this population. The finding that pain catastrophizing predicts cognitive complaints is of considerable interest and has both empirical and theoretical implications for understanding the cognitive problems reported by so many chronic pain patients. This evidence is consistent with McCracken and Iverson, 24 who found a significant association between pain-related anxiety and cognitive complaints for their chronic pain patients. Considerable overlap exists between pain catastrophizing and pain-related anxiety. They are highly correlated (.73) 27, 45 and share common cognitive features that include a magnified appraisal of pain as a source of anxiety and threat, the perception of helplessness in controlling one’s pain, and a tendency toward obsessive preoccupation with the pain stimulus. Moreover, pain catastrophizing and pain-related anxiety have been consistently linked to a number of pain-related variables that can interfere with ongoing attentional processes, thereby compromising cognitive function for people with pain. For example, pain patients who report more pain-related anxiety or catastrophizing about pain have a stronger preference for scanning the body for threatening somatic cues and pain sensations. 23, 44, 45, 52 Roelofs et al 53 found that pain patients who report greater pain-related fear, pain catastrophizing, and pain severity have more severe preoccupation with or attention to pain (eg, pain vigilance). Goubert et al 54 observed that both pain-related fear and pain catastrophizing mediated the relation between neuroticism and pain vigilance and that vigilance to pain is dependent on both pain-related fear and pain catastrophizing. Finally, people who score with higher levels of pain catastrophizing or pain-related fear have more difficulty shifting their attention away from a painful event, disengaging from a pain stimulus, or diverting their attention away from pain-related thoughts. 52, 55, 56, 57, 58 Several researchers have hypothesized an interaction among pain, pain catastrophizing, and pain-related fear in models that attempt to explain the nature of cognitive dysfunction among chronic pain patients. As noted, Eccleston and Crombez 20 hypothesized that the threat value of a pain stimulus will moderate the effect of pain on cognitive function. They suggested that people who exaggerate or exceedingly enhance the threat value of pain will increase their attentional focus on pain at the expense of competing cognitive demands. Indeed, numerous studies identify the effect of pain catastrophizing on magnifying the severity of a pain stimulus and its threat value. 45 In an analysis of the relation between pain-related fear and chronic pain disability, Vlaeyen et al 59 conjectured that a style of catastrophic thinking about pain may be a risk factor for developing pain-related fear. Supporting evidence for this view comes from a study by Crombez et al. 52 Crombez found that students who demonstrate greater catastrophic thinking about pain report more pain-related fear when posed with a potentially strong pain stimulus. Taking these findings collectively, Gracely et al 60 theorized that because people who catastrophize have difficulty disengaging from a painful stimulus, are more vigilant in attending to their pain, and attach more threat to the pain stimulus, 52, 61 pain catastrophizing would logically lead to an increase in pain-related fear, and the fear, in turn, would result in further increased attention to pain. These studies suggest that the perception of pain may reciprocally interact with pain catastrophizing and pain-related anxiety to increase pain intensity and vigilance, and this scenario would disrupt attentional processes that are engaged with ongoing or competing cognitive tasks. Supporting data for this model come from a recent study by Crombez et al 62 who found that, for a group of chronic pain patients, attentional interference was best predicted by an interaction of pain-related fear and pain severity, whereas pain intensity alone was not associated with attentional interference. The failure to find a significant relation between pain intensity and cognitive impairment in the Crombez study is in contrast to several previously published studies that found a positive association between pain intensity and cognitive disturbance. 3, 6, 22, 23 However, these studies failed to account for possible moderators of the relation between pain intensity and cognitive disturbance. Thus, pain severity alone, unless quite severe, 63 may not be sufficient to produce cognitive deficits as previously suggested. 20 This deduction is further supported by our findings and those of McCracken and Iverson. 24 Both studies found that pain severity loses its significant association with cognitive complaints after controlling for, among other covariates, pain catastrophizing and pain-related anxiety, respectively. Finally, we found a significant contribution of female sex to reports of cognitive complaints for our sample. Compared with men, women report more severe pain intensity, 64, 65 show a greater tendency toward pain catastrophizing, 45 and are more likely to become depressed when suffering with a chronic pain problem. 66, 67, 68 As we have noted, pain intensity, pain catastrophizing, and depression have all been linked to cognitive complaints for chronic pain patients in previous studies. However, because we controlled for each of these variables in the present study’s multiple regression analysis, our results suggest a unique contribution of female sex beyond its association with these covariates. Of interest, the McCracken study 24 initially found a small but significant relation between male sex and cognitive complaints, but this association was not maintained for the multiple regression analysis. It is unclear why our female patients reported more severe problems with cognitive function. One possibility is that female pain patients are more inclined to disclose their experience of pain and related symptom complaints than are male pain patients. 69 Thus, it is possible that female sex is associated with cognitive complaints because of differences in response style and the relative preference for symptom reporting that is associated with female sex. The present study has several methodologic limitations. Because the experimental design is cross-sectional, the significant associations obtained do not provide information on causality in considering the underlying direction of these associations. Because the study relies on self-report measures, it is vulnerable to the effects of response style and impression management. Also, because we examined self-reported cognitive complaints among chronic pain patients, the study lacks an objective neuropsychologic assessment of cognitive impairment for these patients. In this regard, the validity of the BSI items as a measure of cognitive impairment is limited by the absence of validity data to support their value as a marker of neurocognitive disturbance. Despite the lack of validity data, the BSI cognitive items have been used to identify cognitive problems among chronic pain patients, 28 and the items do show adequate internal consistency. A further methodologic issue is that the BSI items were constructed to correlate with psychologic distress; therefore, the significant correlation with depression obtained may reflect common measurement variance rather than an association between depression and cognitive impairment per se. Finally, the results of our regression analysis were dependent on the number and range of variables considered for computation. To the extent that we did not account for variables that potentially affect the cognitive function of patients with chronic pain (eg, use of antidepressants 24) or failed to adequately quantify data that were included, our findings may be incomplete. Conclusions The results of this study support previous findings documenting the substantial prevalence of cognitive complaints among people with chronic pain. Consistent with previous studies, our data draw attention to the strong association between depressive symptoms and cognitive complaints among patients with chronic pain. These data suggest that the high comorbidity of depression with chronic pain may, in part, account for the frequent observation that chronic pain patients report cognitive deficits. Our data also highlight the potential role of fatigue in the cognitive problems reported by chronic pain patients and show that women may be particularly vulnerable to the cognitive impairment associated with chronic pain. The results also suggest that pain patients who have a tendency to catastrophize about their pain are at greater risk for experiencing cognitive complaints. These findings suggest that interventions for chronic pain that target depression 70 and pain catastrophizing 71 may potentially have a parallel and positive impact on cognitive function. 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Department of Physical Medicine and Rehabilitation, University of Michigan Health System, Ann Arbor, MI.  Correspondence to Randy S. Roth, PhD, Dept of Physical Medicine and Rehabilitation, University of Michigan Health System, Ann Arbor, MI 48109, Reprints are not available from the authors.
No commercial party having a direct financial interest in the results of the research supporting this article has or will confer a benefit on the author(s) or on any organization with which the author(s) is/are associated. PII: S0003-9993(05)00002-X doi:10.1016/j.apmr.2004.10.041 © 2005 American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation. Published by Elsevier Inc. All rights reserved. | |
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