Behnv. Res. Ther. Vol. 29, No. 5, pp. 435441, 1991 Printed in Great Britain. All rights reserved
ooO5-7967/91 $3.00+ 0.00 Copyright 0 1991Pergamon Press plc
THE EVOLUTION OF CHRONIC BACK PAIN PROBLEMS: A LONGITUDINAL STUDY H. C. PHILIPS and LYNDA GRANT Psychology Department, University Hospital, Shaughnessy Site, Vancouver, British Columbia, Canada V6H 3NI (Received
IO December
1990; received for publication
I5 April 1991)
Summary-A longitudinal evaluation of the recovery from an acute back pain episode was undertaken on 117 sufferers, with assessments at the onset, 3 and 6 months. The number of individuals still reporting pain at 6 months, and therefore qualifying for ‘chronic pain’, was considerably higher than expected (40%). At 6 months, the persisting pain problems were found to be moderate to severe in intensity in approx. 20% of cases. Despite the pain, the chronic sufferers showed gradual continuing adjustments to it, re-establishing activities despite pain. Most of the change in the pain components (cognitive, subjective, behavioral, depression, anxiety) occur in the first 3 months, after which considerable stability is evident in the residual problem. In contrast, the impact of the pain and the consequent disability decline more markedly and continue to do so right up to the 6 month point. There was no evidence of chronic pain evolving and growing, but rather of a persistence of the acute presentation.
INTRODUCTION
It is commonly believed that chronic back pain problems develop gradually over the months following acute injury. Traditionally ‘chronic’ was defined as pain that was present 6 months post-onset, but more recently (International Association for Pain-Classification of Chronic Pain, 1986) the cut-off has been moved forward to the point of predicted healing (i.e. at 3 months). However, there is a notable lack of investigations of the chronic process over the early months, either in the orthopaedic or behavioral medical literature. Two assumptions are made about the chronic pain process. First, it is thought that acute injuries resolve themselves quickly for the majority of people. For 90% of cases of acute back pain, pain behavior and experience will reduce gradually over the first 4-12 weeks (Nachemson, 1982). Second, it is assumed that only a small percent of individuals who sustain an acute injury will in fact end up with a chronic pain problem. Figures vary but it is believed that from 10 to 15% of individuals will fall into the chronic category (Leavitt, Beyer & Johnston, 1972; Nachemson, 1982; White, 1966). Without a longitudinal evaluation, these beliefs about the development or evolution of chronic back pain cannot be assessed. Nachemson (1984) felt the major challenge in orthopaedics in the 1980s was to consider how to prevent disabling and costly chronic back pain problems. The aim of this investigation is to provide a longitudinal perspective on the evolution of chronic back pain problems. Cross-sectional evaluation at the acute onset of back pain, the sub-acute stage (3 months), and the chronic stage (6 months) allowed the assessment of psychological reactions and disability over time (Philips & Grant, 1991). By taking this approach to the evolution of chronic pain, it is possible to begin to delineate the process by which chronic pain problems develop. METHOD Subjects
117 acute back-pain sufferers were referred to the research project by private practitioners, physiotherapists and emergency physicians. The requirement for participation in the research was that there be no neural or discal signs and that the pain be the first episode of acute pain (rather than a continuation of a longstanding back problem), and that the onset of the pain had been within 15 days of their visit to a physician. In fact, the average number of days from pain onset BRT 29,SD
435
436
H.C. PHILIPSand LYNDAGRANT
to the psychologist’s visit was 7.9 (SD 4.6). The average age of this group was 32 (SD 7.6) with a male/female ratio of 3 : 4. Further details of acute group can be found in Philips and Grant (199 1; Philips, Grant & Berkowitz, 1991). To encourage Ss to attend follow-up sessions, even if pain-free, a fee of $75 was paid to Ss on their last session conditional upon completing all questionnaires and sessions. An attribution rate of 2 1% was incurred over the 6 month period, due to loss of contact, illness, reluctance to attend, etc. These occurred for the most part between the 3 and 6 month visits. Procedure Ss were seen for 45 min in their first assessment. They returned completed questionnaires provided prior to the appointment, and took part in a structured interview. Follow-up contact was made at 3 and 6 months post-pain onset. At these intervals questionnaires were repeated and a shorter structured interview undertaken (30 min). Details of the rehabilitation approach used with these Ss can be found in a companion article on the prevention of chronic pain (Philips et al., 1991). For purposes of this study, however, it is merely necessary to report that the comparison of two different rehabilitation approaches produced no significant difference in outcome (Philips et al., 1991). This provides the opportunity to analyze the longitudinal data without considering group differences. The three evaluation points are called Acute (onset), Sub-chronic (3 months post-onset), and Chronic (6 months post-onset). Measures The battery of questionnaires utilized for the evaluation of the pain problem and emotional correlates was as follows. Beck Depression Inventory (Beck, Ward, Mendelson, Mock & Erbaugh, 1961). The Spielberger State-Trait Inventory (Spielberger, 1983) Pain Behavior Checklist (Philips & Jahanshahi, 1985), Cognitive Evaluation Questionnaire (Philips, 1989) Sickness Impact Inventory (Bergner, Butto & Gilson, 1981) and Pain Questionnaire (Hunter, 1983). A Disability Index was calculated from estimates given by Ss of the percent pain interfered with different aspects of their lives (e.g. sleep, work, exercise, family relationships, housework and social life). This index was a simple average of the reported percentage interference on six aspects of life, given by Ss in the structured interview. In addition, the structured interview was designed in order to collect demographic information, estimates of the psychological and physical effects of the pain episode, the degree of handicap produced by the current pain experience, attitude of patients to their rehabilitation, rough levels of fitness as assessed by the patient, and amount of exercise. (Examples of the structured interview are available by request from the authors.) RESULTS
The size of the chronic pain problem Table 1 contains the means and standard deviations on the major measures, both from the psychological inventories and the structured interview. The acute assessment occurred on average 7.9 days post onset (SD 4.6) at which time all the Ss (n = 117) still reported pain. When given a range from 0 to 100 (nothing to excruciating incapacitating pain), Ss reported an average intensity of 46.8. More than half reported continuous discomfort or pain. The change in the sample size on Table 1 at each of the assessment points is due to the reduction is Ss still in pain over the 6 month period. At the 3 month point 39, or 43.9%, of the original sample were still reporting discomforts/pain. At 6 months 37, or 40.2%, were still reporting pain. (Table 1 reports the results of only those reporting pain.) Course Ss who became pain-free during the 6 month period were asked about the time-course of recovery at the 3 month point. Pain-free Ss reported that it had taken 4.3 weeks (SD 3.2) on average before they attained this status. At 6 months, the pain-free Ss reported an average of 6.4 weeks
The evolution
of chronic
back pain
431
Table I. Mean (SD) of dependent measures of pain and the pain problem for the Ss in pain at acute onset (< I5 days since onset), sub-chronic (3 months post-onset) and chronic point (6 months oost-onset)
Average pain intensity (&loo) Pain range (CLlOO) % continuous % litigating Pain questionnaire sensory Affective Pain behavior Avoidance Complaint Cognitive evaluation Sickness Impact Profile S14 (general impact) Disability Index Beck Depression Inventory State/Trait Anxiety Inventory Stait
Trait
Acute ??=I17
Sub-chronic n = 39
46.8 (17.4) 17.5-71.6 63 48
36.4 (21.8) 13.5-54.3 49 23
Chronic n = 37 31.4(18.0) 11.746.3 46 21
0.98 (0.56) I .39 (0.68)
0.88 (0.64) I .27 (0.72)
0.72 (0.42) 1.16(0.70)
47% (20.9) 67% (22.0) 46.6 (23.5)
40% (27.0) 52% (27.0) 46.7 (24.6)
39% (25.0) 53% (24.0) 40.5 (24.4)
18.10(12.6) 43.0 (23.7) 9.03 (7.6)
12.7(13.5) 21.1 (23.2) 9.03 (8.7)
8.6 (9.2) 31.2(18.3) 8.68 (8.2)
48 oercentile 46 percentile
43 oercentile 54 percentile
43 oercentile 46 percentile
or 1; months recovery time. Between 3 and 6 months, there was a marked stability in response measures (see Table 1). Reduction in response occurred primarily in the first 3 months. The severity and course of chronic pain problems It is possible to evaluate the severity of the pain experienced by the Ss from a number of different perspectives. In the structured interview, all Ss were asked to rate the severity of their pain from 0 (no pain) to 5 (very severe). Figure 1 below gives a histogram of these results. 19% of cases reported moderate to severe continuing pain at the 3 month point. There is only a modest increase in this percentage when the reports are considered at the 6 month point (20% report moderate to severe pain). A second way of evaluating the severity of the pain at the sub-chronic/chronic stages is to consider the results on a number of indices of pain (see Table 1). There is a progressive drop in all but one measure across the 6 month period. The greatest decrement can be seen in the first 3
cl
Sub-chronic
umlChronic
Pain-free Fig.
Mild
e Moderate
Severe
Very severe
1.Ss’ estimates of the severity of their pain problem on a 5 point scale (no pain, mild pain, moderate, severe and very severe) at the sub-chronic
and chronic
assessment
points.
H. C. PHILIPS and LYNDAGRANT
438
Table 2. Relationship between Disability Index and pain intensity rating at the 3 assessment points. Acute, sub-chronic and chronic expressed as-a correlation coefficient Pain intensity Disabilitv
Acute Sub-chronic Chronic
Index
Acute 0.44
Sub-chronic 0.81
Table 3. Estimates
Acute n = I17
rating Chronic
0.73
of the effects of pain on daily life and emotions, as % increase or decrease Sub-chronic n =39
Chronic n = 37
Work reduction ‘Down-time’ Sleep disturbance Exercise
-63.3 + 32.6 f52.3 -68.8
-4.4 + 13.2 + 24.1 -40.9
- 2.2 f4.9 +21.1 - 25.6
Frustration Anxiety Low spirits
+ 34.5 +28.5 +23.0
+20.2 + 19.9 + 14.4
+ 15.3 + 16.5 + 15.1
months, with the exception of pain cognitions. Comparisons of the mean levels (paired c-test) showed significant reductions over the 6 months in pain intensity (t = 4.65,
ooO5-7967/91 $3.00+ 0.00 Copyright 0 1991Pergamon Press plc
THE EVOLUTION OF CHRONIC BACK PAIN PROBLEMS: A LONGITUDINAL STUDY H. C. PHILIPS and LYNDA GRANT Psychology Department, University Hospital, Shaughnessy Site, Vancouver, British Columbia, Canada V6H 3NI (Received
IO December
1990; received for publication
I5 April 1991)
Summary-A longitudinal evaluation of the recovery from an acute back pain episode was undertaken on 117 sufferers, with assessments at the onset, 3 and 6 months. The number of individuals still reporting pain at 6 months, and therefore qualifying for ‘chronic pain’, was considerably higher than expected (40%). At 6 months, the persisting pain problems were found to be moderate to severe in intensity in approx. 20% of cases. Despite the pain, the chronic sufferers showed gradual continuing adjustments to it, re-establishing activities despite pain. Most of the change in the pain components (cognitive, subjective, behavioral, depression, anxiety) occur in the first 3 months, after which considerable stability is evident in the residual problem. In contrast, the impact of the pain and the consequent disability decline more markedly and continue to do so right up to the 6 month point. There was no evidence of chronic pain evolving and growing, but rather of a persistence of the acute presentation.
INTRODUCTION
It is commonly believed that chronic back pain problems develop gradually over the months following acute injury. Traditionally ‘chronic’ was defined as pain that was present 6 months post-onset, but more recently (International Association for Pain-Classification of Chronic Pain, 1986) the cut-off has been moved forward to the point of predicted healing (i.e. at 3 months). However, there is a notable lack of investigations of the chronic process over the early months, either in the orthopaedic or behavioral medical literature. Two assumptions are made about the chronic pain process. First, it is thought that acute injuries resolve themselves quickly for the majority of people. For 90% of cases of acute back pain, pain behavior and experience will reduce gradually over the first 4-12 weeks (Nachemson, 1982). Second, it is assumed that only a small percent of individuals who sustain an acute injury will in fact end up with a chronic pain problem. Figures vary but it is believed that from 10 to 15% of individuals will fall into the chronic category (Leavitt, Beyer & Johnston, 1972; Nachemson, 1982; White, 1966). Without a longitudinal evaluation, these beliefs about the development or evolution of chronic back pain cannot be assessed. Nachemson (1984) felt the major challenge in orthopaedics in the 1980s was to consider how to prevent disabling and costly chronic back pain problems. The aim of this investigation is to provide a longitudinal perspective on the evolution of chronic back pain problems. Cross-sectional evaluation at the acute onset of back pain, the sub-acute stage (3 months), and the chronic stage (6 months) allowed the assessment of psychological reactions and disability over time (Philips & Grant, 1991). By taking this approach to the evolution of chronic pain, it is possible to begin to delineate the process by which chronic pain problems develop. METHOD Subjects
117 acute back-pain sufferers were referred to the research project by private practitioners, physiotherapists and emergency physicians. The requirement for participation in the research was that there be no neural or discal signs and that the pain be the first episode of acute pain (rather than a continuation of a longstanding back problem), and that the onset of the pain had been within 15 days of their visit to a physician. In fact, the average number of days from pain onset BRT 29,SD
435
436
H.C. PHILIPSand LYNDAGRANT
to the psychologist’s visit was 7.9 (SD 4.6). The average age of this group was 32 (SD 7.6) with a male/female ratio of 3 : 4. Further details of acute group can be found in Philips and Grant (199 1; Philips, Grant & Berkowitz, 1991). To encourage Ss to attend follow-up sessions, even if pain-free, a fee of $75 was paid to Ss on their last session conditional upon completing all questionnaires and sessions. An attribution rate of 2 1% was incurred over the 6 month period, due to loss of contact, illness, reluctance to attend, etc. These occurred for the most part between the 3 and 6 month visits. Procedure Ss were seen for 45 min in their first assessment. They returned completed questionnaires provided prior to the appointment, and took part in a structured interview. Follow-up contact was made at 3 and 6 months post-pain onset. At these intervals questionnaires were repeated and a shorter structured interview undertaken (30 min). Details of the rehabilitation approach used with these Ss can be found in a companion article on the prevention of chronic pain (Philips et al., 1991). For purposes of this study, however, it is merely necessary to report that the comparison of two different rehabilitation approaches produced no significant difference in outcome (Philips et al., 1991). This provides the opportunity to analyze the longitudinal data without considering group differences. The three evaluation points are called Acute (onset), Sub-chronic (3 months post-onset), and Chronic (6 months post-onset). Measures The battery of questionnaires utilized for the evaluation of the pain problem and emotional correlates was as follows. Beck Depression Inventory (Beck, Ward, Mendelson, Mock & Erbaugh, 1961). The Spielberger State-Trait Inventory (Spielberger, 1983) Pain Behavior Checklist (Philips & Jahanshahi, 1985), Cognitive Evaluation Questionnaire (Philips, 1989) Sickness Impact Inventory (Bergner, Butto & Gilson, 1981) and Pain Questionnaire (Hunter, 1983). A Disability Index was calculated from estimates given by Ss of the percent pain interfered with different aspects of their lives (e.g. sleep, work, exercise, family relationships, housework and social life). This index was a simple average of the reported percentage interference on six aspects of life, given by Ss in the structured interview. In addition, the structured interview was designed in order to collect demographic information, estimates of the psychological and physical effects of the pain episode, the degree of handicap produced by the current pain experience, attitude of patients to their rehabilitation, rough levels of fitness as assessed by the patient, and amount of exercise. (Examples of the structured interview are available by request from the authors.) RESULTS
The size of the chronic pain problem Table 1 contains the means and standard deviations on the major measures, both from the psychological inventories and the structured interview. The acute assessment occurred on average 7.9 days post onset (SD 4.6) at which time all the Ss (n = 117) still reported pain. When given a range from 0 to 100 (nothing to excruciating incapacitating pain), Ss reported an average intensity of 46.8. More than half reported continuous discomfort or pain. The change in the sample size on Table 1 at each of the assessment points is due to the reduction is Ss still in pain over the 6 month period. At the 3 month point 39, or 43.9%, of the original sample were still reporting discomforts/pain. At 6 months 37, or 40.2%, were still reporting pain. (Table 1 reports the results of only those reporting pain.) Course Ss who became pain-free during the 6 month period were asked about the time-course of recovery at the 3 month point. Pain-free Ss reported that it had taken 4.3 weeks (SD 3.2) on average before they attained this status. At 6 months, the pain-free Ss reported an average of 6.4 weeks
The evolution
of chronic
back pain
431
Table I. Mean (SD) of dependent measures of pain and the pain problem for the Ss in pain at acute onset (< I5 days since onset), sub-chronic (3 months post-onset) and chronic point (6 months oost-onset)
Average pain intensity (&loo) Pain range (CLlOO) % continuous % litigating Pain questionnaire sensory Affective Pain behavior Avoidance Complaint Cognitive evaluation Sickness Impact Profile S14 (general impact) Disability Index Beck Depression Inventory State/Trait Anxiety Inventory Stait
Trait
Acute ??=I17
Sub-chronic n = 39
46.8 (17.4) 17.5-71.6 63 48
36.4 (21.8) 13.5-54.3 49 23
Chronic n = 37 31.4(18.0) 11.746.3 46 21
0.98 (0.56) I .39 (0.68)
0.88 (0.64) I .27 (0.72)
0.72 (0.42) 1.16(0.70)
47% (20.9) 67% (22.0) 46.6 (23.5)
40% (27.0) 52% (27.0) 46.7 (24.6)
39% (25.0) 53% (24.0) 40.5 (24.4)
18.10(12.6) 43.0 (23.7) 9.03 (7.6)
12.7(13.5) 21.1 (23.2) 9.03 (8.7)
8.6 (9.2) 31.2(18.3) 8.68 (8.2)
48 oercentile 46 percentile
43 oercentile 54 percentile
43 oercentile 46 percentile
or 1; months recovery time. Between 3 and 6 months, there was a marked stability in response measures (see Table 1). Reduction in response occurred primarily in the first 3 months. The severity and course of chronic pain problems It is possible to evaluate the severity of the pain experienced by the Ss from a number of different perspectives. In the structured interview, all Ss were asked to rate the severity of their pain from 0 (no pain) to 5 (very severe). Figure 1 below gives a histogram of these results. 19% of cases reported moderate to severe continuing pain at the 3 month point. There is only a modest increase in this percentage when the reports are considered at the 6 month point (20% report moderate to severe pain). A second way of evaluating the severity of the pain at the sub-chronic/chronic stages is to consider the results on a number of indices of pain (see Table 1). There is a progressive drop in all but one measure across the 6 month period. The greatest decrement can be seen in the first 3
cl
Sub-chronic
umlChronic
Pain-free Fig.
Mild
e Moderate
Severe
Very severe
1.Ss’ estimates of the severity of their pain problem on a 5 point scale (no pain, mild pain, moderate, severe and very severe) at the sub-chronic
and chronic
assessment
points.
H. C. PHILIPS and LYNDAGRANT
438
Table 2. Relationship between Disability Index and pain intensity rating at the 3 assessment points. Acute, sub-chronic and chronic expressed as-a correlation coefficient Pain intensity Disabilitv
Acute Sub-chronic Chronic
Index
Acute 0.44
Sub-chronic 0.81
Table 3. Estimates
Acute n = I17
rating Chronic
0.73
of the effects of pain on daily life and emotions, as % increase or decrease Sub-chronic n =39
Chronic n = 37
Work reduction ‘Down-time’ Sleep disturbance Exercise
-63.3 + 32.6 f52.3 -68.8
-4.4 + 13.2 + 24.1 -40.9
- 2.2 f4.9 +21.1 - 25.6
Frustration Anxiety Low spirits
+ 34.5 +28.5 +23.0
+20.2 + 19.9 + 14.4
+ 15.3 + 16.5 + 15.1
months, with the exception of pain cognitions. Comparisons of the mean levels (paired c-test) showed significant reductions over the 6 months in pain intensity (t = 4.65,
