The accuracy of remembering chronic pain

The accuracy of remembering chronic pain

Pain, 13 (1982) 281-285 Elsevier Biomedical Press 281 The Accuracy of Remembering Chronic Pain Steven J. Linton i., and Lennart Melin 2 Deparament o...

282KB Sizes 99 Downloads 64 Views

Pain, 13 (1982) 281-285 Elsevier Biomedical Press

281

The Accuracy of Remembering Chronic Pain Steven J. Linton i., and Lennart Melin 2 Deparament of Applied Psychology, Uppsala University, PO Box 1225, S-751 42 Uppsala (Sweden), and * Department of Psychiatry, Unioz.rsityof Trondhein~ PO Box 3008, N- 7001 Trondheim (Norway) (Received 23 September 1981, accepted 17 November lqSl)

Summary Twelve chronic pain patients were employed in an investigation of the accuracy of memory for chronic pain, Subjects first made pain ratings before entering a treatment program. At dismissal 3-11 weeks later they were asked to remember how rauch pain they had had at baseline. Results show that patients remembered having significantly more pain than they actually rated during the baseline period. Caution is therefore warranted when using post-hoe pain measures with chronic pain patients.

lnWoduction

Memory for pain plays an important role in the evaluation of patients. Clinicians may rely on past accounts of pain in diagnosing the patient's problem and in evaluating treatment outcomes. For example, in chronic pain clinics patients may rate their pain level on a scale from 0 to 100 and these ratings may be made for past as well as for present pain levels. In operant pain treatment programs this is considered to be particularly relevant since ratings may occur infrequently or post hoc in an effort to decrease verbal pain behaviors [ 1]. The classic study of the operant pain treatment program, for instance, relied entirely upon post-hoc ~'atings of pain levels [2]. Similarly, clinicians and researchers doing follow-up evaluations of treatment may ask patients to rate their pain in comparison with admission levels. Consequently. several evaluation techniques both in research and in the clinic rely heavily on patients accurately remembering how much pain they had at an earlier i Currently at the University of Trcadheim, Department of Psychiatry, PO Box 3008, N-7001 Trondheim, Norway. 2 To whom reprint requests should be addressed. 0304-3959/82/0000-0000/$02.75 © 1982 Elsevier Biomedical Press

282 point in time and this point c~m be as much as 6 months or a year earlier. One is generally skeptical of the accuracy of post-hoe ratings, since they may be influenced by what happens during the interim between experience and recall. In this respect, Turk and Genest [6] have criticized Fordyce et al.'s [2] use ,of post-hoe pain measures as being possibly invalid. There is little research, however, which examines the accuracy of recalled pain. Hunter et al. [3], in the one study that has looked at this problem, found that recall of pain was surprisingly accurate up to 5 days after having experienced an episode of acute pain. Longer recall periods are more relevant, however, in the chronic pain situation because pain or its treatn~ent ordinarily continues for at least several weeks. Furthermore, in the evaluation of a treatment program, the treatment experienced may systematically influence the remembering of pretreatment pain levels. The purpose of this study was to investigate the accuracy of post-hoe pain intensity ratings for chronic pain patients with a recall interval of several weeks. Patients undergoing treatment for chronic pain were asked to rate their pain just prior to their admission and then at dismissal they were asked to remember how much pain they had had at baseline.

Method

Subjects Twelve patients (6 males, 6 fert~ales, mean a g e - 48) seeking help from the day ward of the Department of Physical Rehabilitation, University Hospital, Uppsala, Sweden, participated in the study. All subjects had had pain for more than 6 months dmation (mean sick-listed length = 2 years) and the primary site of the pain was in the b a ~ or joints.

Procedure Patients were contacted prior to their admission to the day ward and asked if they would voluntarily participate in the study. Shortly before their scheduled admission, the patients were interviewed and baseline pain ratings were obtained. Pain was measured by having patients rate their pain on a scale from 0 to 100 where 0 was no pain and 100 was terrible, excruciating pain. The qualities of this scale are discussed in greater detail by Kremer et al. [4]. Patients were given a supply of pain rating blanks and instructed to fill them in for a 2 week period. During the course of treatment, patients were periodically asked to rate their pain. At discharge pain ratings for 1 week were collected, and patients were given an evaluation questionnaire consisting of 8 questions. One of the questions asked the participants to recall, and rate on the same 0-100 scale, how much pain they had had at baseline: 'Think back and try to remember how much pain you had at the time you entered the day ward. How much pain did you have then?.' These 'remembered pain' ratings were made between 3 and 11 weeks after baseline (mean = 51 days, range = 24-75 days).

283

Results Of the i2 patients, 11 (927O) remembered the pain as being more severe than their actual baseline rating. The mean actual baseline rating was 56, while the recalled r~fing was 69. This 197o difference is significant (Wilcoxon test, P < 0.01). Three Spearman rank correlations were calculated in an attempt to find the source of ;he difference in ratings. First, the correlation between actual baseline ratings and remembered baseline ratings was a significant 0.53 ( P < 0.05, one-tail). One possible explanation of the difference was that the degree of improvement systematically affected recall ratings. The correlation between error size and amount of improvement (actual baseline pain minus dismissal pain) was, however, not significant ( r - 0.23, P > 0.05). Another possibility was that remembering was related to the recall interval, but the correlation between error size and the interval length was not significant (r = 0.06, P :> 0.05).

Discussion The results show that there was a systematic and significant overestimation of recalled baseline pain ratings. This has important implications for the evaluation of pain in research and in the clinic. Namely, post-hoe evaluations which rely on patients remembering how much pain they had at a period some weeks in the past are inaccurate. Moreover, the error is systematic so that recalled pain is significantly greater than the baseline pain ratings previously made. For research this means that post-hoc evaluations are at best questionable and at worst are significantly exaggerating actual treatment gains. Fordyce et al. [2, p. 4061, for example, asked patients .some 22 months after the completion of treatment t o ' ... rate on a 10-point scale the amount of pain they remembered themselves as having at the time of admission and discharge from the program and at the time of completing the follow-up questionnaire.' While Fordyce et al. [2] observed a 287O reduction in pain, roughly 20% of that reduction might be accounted for by the systematic inflation of making post-hoe baseline pain ratings. As another example, Roberts and Reinhardt [5, p. 155] asked patients '... to rate the change in their pain since evaluation...' 1-8 years after that evaluation. The results of the present investigation are somewhat different from those obtained by Hunter et al. [3]. They found that patients remembered acute pain, lasting from 2 to 4 h and experienced after a neurosurgical investigation, surprisingly well even after 5 days. There are two major differences between the Hunter et al. study and the present study which may explain the discrepancy in the accuracy of remembering pain First, Hunter et al. studied acute pain associated with a very specific event, while chronic pain not associated with any particular event was looked at here. Further, the Hunter et al. study used rather short recall intervals with the longest being 5 days. Longer periods ranging from 3 to 11 weeks were used in the present investigation. One might conclude then that memory for pain is accurate if it is related to a specific event (e.g. acute) and if the recall period is relatively short,

284

while memory for pain is inaccurate if the pain is long standing and the recall period is long. In clinical practice one could presumably rely upon the pain reports of a patient that broke his/her arm the week before. On the other hand, asking a chronic pain patient how much pain he/she had a month ago (e.g. before the start of treatment) is likely to result in an inaccurate rating. ~ The reason that acute, short recall inte~'al ratings are more accurate than chronic, long recall ratings may be related primarily to the stimulus properties surrounding the pain. Acute pain, especially if it is severe, is a very discriminable event and it usually occurs in very discriminable situations, e.g. after an accident or an operation. Chronic pain, however, may be relatively constant and small systematic changes over time are therefore difficult to discriminate. Furthermore, since chronic back or joint pain is usually diffuse it may be even more difficult to discriminate changes in intensity. The recall interval is also of intportance, but it probably influences accuracy to only a small degree, in comparison with stimulus properties, with the time intervals discussed here. Why patients constantly overestimated their baseline pain levels is unclear. Overestimation was not related to either the amount of treatment improvement or to the length of the recall interval. One factor not studied, but which could possibly account for these results, is demand characteristics. This seems unlikely, however, since although patients tended to inflate their baseline scores (and consequently the difference between baseline and discharge pain ratings, i.e. improvement in pain), there was little evidence that this overestimation was reflected in their perception of their own improvement. Specifically, one question on the questionn~J,'e described earlier was: 'compare how much pain you have now with how much pain you had when you entered the program.' If demand factors were operating one would expect patients to answer that they had considerable reductions in pain, an answer which would coincide with the difference between remembered baseline pain and discharge pain levels. However, the average response to the above question was situated exactly between the categories of 'a little less pain' and 'about the same pain.' Thus, while there was a relati'Tely large difference between remembered baseline and discharge pain ratings (mean decrease = 27 points or a 39~ decrease), patients still perceived only a small improvement in their pain condition, A final point is that further research in this area is clearly warranted to replicate these findings and to then isolate the factors causing the overestimation. In summary, while the reasons for the large systematic overestimation in recalled pain are somewhat puzzling, the present study provides little support for the use of post-hoc measures of pain with chronic pain patients.

References 1 Fordyce, W., Behavioral Methods for Chronic Pain and Illness, Mosby, St. Louis, Mo., 1976. 2 Fordyce, W., Fowler, R., Lehmann, J., DeLateur, B., Sand, P. and Trieschmann, R., Operant conditioning in the treatment of chronic pain, Arch. phys. Med., 54 (1973) 399-408. 3 Hunter, M., Phi!ip~, C. ,~n~ Rachman, S., Memory for pain, Pain, 6 (1979) 35-46.

285 4 Kremer, E., Atkinson, J. and lgnelzi, R., Measurement of pain: patient preference does not confound pain measurement, Pain, 10 (1981) 241-248. 5 Roberts, A. and Reinhardt, L., The behavioral management of chronic pain: long-term follow-up with comparison groups, Pain, 8 (1980) 151-162. 6 Turk, D. and Gencst, M,, Regulation of pain: the application of cognitive and behavioral techniques for prevention and remcdia~ion. In: P.C. Kendall and $.D. Hoilon (Eds.), Cognitive-Behavioral Interventions: Theory, Research, and Practice, Academic Press, New York, 1979, pp. 287-318.