F ACULTY OF M EDIC INE
–
U N IVERS ITY OF P ORTO
Department of Biostatistics and Medical Informatics
Introdução à Medicina 2005/2006
Almeida,F.;
Conceição, C.;
Costa, M.; Faria, C.; med05192@med.up.pt
Gonçalves, C.; med05172@med.up.pt
med05173@med.up.pt med05033@med.up.pt
Machado, C.; med05168@med.up.pt
Martins, C.; med05170@med.up.pt med05229@med.up.pt
Martins, M.; med05024@med.up.pt
Soares,C.; med05165@med.up.pt
Adviser: Luís Filipe R. Azevedo, lazevedo@med.up.pt
, Class: 6
Abstract
Introduction
Pain is an unpleasant sensory and emotional experience which affects 10 to 15% of world’s population.
Two kinds of pain can be distinguish: acute pain and chronic pain, which differ mainly in duration.
Aim
The objective of our study is to make a systematic review of literature about risk factors for evolution into chronicity in individuals with acute pain.
Methods
A systematic review was performed. Initially an electronic search was carried out at Medline and Scopus databases. Afterwards the papers obtained were accessed by the application of inclusion/exclusion criteria previously defined. Two reviewers blind to each other coded each study as included or excluded first by abstract and the remaining papers by full text. Data was then extracted and analysed.
Results
500 publications were found in Medline and Scopus baselines, using “Chronicity AND pain”. Five publications (all cohort studies) studied risk factors that influence the evolution of acute pain into chronic pain and met acceptability criteria for methodology, psychological measurement and statistical analysis.
A great number of painful areas (>3) increase the risk of chronicity (OR 15.8 (4.53-55.3)) as well as, to a lesser extent, severe (OR 5.89 (2.84-12.20)) and extreme (OR 5.69 (2.73-11.89)) disability. Psychological and social factors are significant too, leading to chronicity when there is depression (OR 2.47 (1.66-
3.67)) and social dysfunction (OR 2.79 (1.98-3.93)). When there are no light duties on return to work (OR
1.99 (1.39-2.86)), after absence for disability caused by pain, and there is the need to lift objects for a great part of the working day (OR 2.04 (1.41-2.96)), pain tends to persist.
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F ACULTY OF M EDIC INE
–
U N IVERS ITY OF P ORTO
Department of Biostatistics and Medical Informatics
Introdução à Medicina 2005/2006
Discussion
Physical factors (number of painful areas and severe and extreme disability) seam to play the greatest influence on developing chronicity. Psychosocial (depression and social dysfunction) and workplace factors also influence the evolution of acute pain into chronic pain. Companies could benefit from having special tasks for people recovering from acute pain and a psycho logician available for it’s employees.
Further studies should be carried out, as this is an important issue with psychological, social and economic implications.
Key-words: Systematic Review, Pain , Chronic Pain, Low Back Pain, Neck Pain, Risk
Factors
Introduction
Pain can be defined as an unpleasant sensory and emotional experience associated with actual or potential tissue damage or described in terms of such damage (definition of
IASP).[1]
Pain is always subjective. Although it is usually associated with tissue damages it can, however, be reported without evidence of such damages, usually for psychological reasons.
It is important to distinguish two types of pain: acute pain and chronic pain. IASP defines chronic pain as a pain without apparent biological value that has persisted beyond the normal tissue healing time (taken to be three months), whereas acute pain tends to have shorter duration, as well as it is connected with tissue lesions. Chronic pain, opposite to acute pain, needs a rehabilitative rather than a treatment model [2].
Other definitions for chronic pain are as well considered. For example, “current continuous or intermittent pain or discomfort which has persisted for more than three months, with recent or frequent seeking of treatment or use of analgesic medication [3].
Chronic pain is among the most disabling and costing afflictions in North America,
Europe and Australia [4]. It is a common cause of suffering, disability and economic adversity in the community that needs to be understood in a multi-dimensional way [2].
More women than men are affected by chronic pain and prevalence increases with age
[2]. It is estimated that between 10 and 15 % of the population suffer from it [2].
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F ACULTY OF M EDIC INE
–
U N IVERS ITY OF P ORTO
Department of Biostatistics and Medical Informatics
Introdução à Medicina 2005/2006
It was proposed by Von Korff [5] the assessment of chronic pain in three dimensions: severity or intensity, duration and impact.
Chronic non-malignant pain is commonest at limbs and joints, at the back, as well as at neck and head [6][7].
Pain has a deep impact on suffers, as it prorogues a sense of loss of their lives, due to loss of confidence and self-esteem associated with psychological, social and economical implications [2].
To manage chronic pain, two issues should be take in count: treatment and rehabilitation and for both, many methods can be used, such as drug therapy, invasive therapies and nerve blocks, physiotherapy, transcutaneous electronic nerve stimulation (TENS) as well as psychological approaches and alternative therapies (as acupuncture, osteopathy and homeopathy) [2] .
However, these types of pain are intimately correlated; acute pain can conduce to chronic pain and many factors are in the origin of such transition. Individual factors, such as obesity, psychological factors as anxiety, insomnia and severe depression, and workplace factors (as the type and hours of work) seem to be in the origin of this transition. It is reported that workers with heavy jobs (such as nurses or drivers), tend to developed chronic pain, especially when such is related with monetary compensations due to inability to do some jobs [8].
Chronic pain can lead to loss of employment, loss of social and home roles, sleep disorders, having such psychological, social and economic implications that it may affect intimate social or even sexual relationships [2]. Due to that, it is of major importance to study how we can transit from acute to chronic pain.
The objective of our study is to make a systematic review of literature about risk factors for evolution into chronicity in individuals with acute pain.
Participants and Methods
Study Design
Our study is a systematic review of cohort studies that have already been done. These cohort studies were selected by applying the criteria described bellow in the papers
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F ACULTY OF M EDIC INE
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U N IVERS ITY OF P ORTO
Department of Biostatistics and Medical Informatics
Introdução à Medicina 2005/2006 obtained with the query “Chronicity AND Pain” at Medline and Scopus data bases using
‘Humans’ as a limit and no language restriction.
Scope of the study
The selection criterion for inclusion of studies was:

Cohort studies that refer to the factors which influence the evolution of acute pain into chronic pain.
The exclusion criteria were:

Language restriction: only studies in English or Portuguese would be included.

Studies that are not connected with the context of our review.

Studies that do not include cohort studies.

Studies that do not refer the evolution of acute pain into chronic.
Searching
Electronic database search of Medline with query “Chronicity AND Pain” were carried out in November 2005, with no language restriction and ‘Humans’ as only limit, resulting in 376 hits. The papers were divided into 4 groups and each one reviewed by abstract for exclusion criteria. 307 articles were excluded at this point. A further electronic search for the remaining papers was carried out on journals at the “Biblioteca
Virtual da Universidade do Porto” for the full text article. 26 articles were found and review by full text for inclusion/exclusion criteria. 3 articles were identified reporting cohort studies on factors which influence the evolution of acute pain into chronic pain.
A search was also made at Scopus with the same query, in March 2006: 505 papers were obtained. 361 were excluded because they were the same that were found at
Medline . The remaining articles were reviewed by the same processes described above.
8 were selected and reviewed by full text for inclusion/exclusion criteria. In this search
2 articles were obtained.
Variables Description
We considered as dependent variable the chronic pain and as independent variables the risk factors that influence the evolutions of acute pain to chronic pain that we are searching for.
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F ACULTY OF M EDIC INE
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U N IVERS ITY OF P ORTO
Department of Biostatistics and Medical Informatics
Introdução à Medicina 2005/2006
Assessment Protocol.
The revision by abstract was performed by 4 groups (one group of 3 reviewers and three groups of 2 reviewers). A sample of papers (n=6) were reviewed by all 9 reviewers who then met to discuss and reach agreement on any differences. Afterwards, two groups reviewed 93 articles and the other two 92. The reviewers, each blind to the others’ assessment, coded each paper as Included or Excluded on the basis of predetermined criteria. They then met to discuss and reach agreement on any differences in coding.
The revision by full text was performed by the same 4 groups. Three groups reviewed
17 articles and one group 18 articles. The reviewers, each blind to the others’ assessment, coded each paper as Included or Excluded on the basis of predetermined criteria. They then met to discuss and reach agreement on any differences in coding.
Assessment of Quality Criteria Protocol.
Each of the following criteria was examined for presence or absence in the study reports:

The sample of patients is representative and homogeneous

Patients are homogeneous with respect to prognostic risk and exposure to factors

The follow up is complete

Measurements of the outcomes are made in the same way on both groups (exposed and unexposed)
When the presence or absence of the criterion was not clear, the reviewers discussed to reach an agreement.
Statistic Analysis
To statistically analyse the results obtained, we extracted the odds ratio connected to the factors studied from each article.
We used SPSS 14.0
to analyse the relative and absolute frequency of the selected and exclude articles. This software was also used to store the data obtained.
Results
Research at Medline [16] database resulted in 376 papers. When reviewed by abstract,
307 articles were excluded. 26 articles were found in full text type. Only 3 articles of
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F ACULTY OF M EDIC INE
–
U N IVERS ITY OF P ORTO
Department of Biostatistics and Medical Informatics
Introdução à Medicina 2005/2006 these were identified reporting cohort studies in factors which influence the evolution of acute pain into chronic pain.
Scopus [17] research resulted in 505 papers. 361 were excluded because they were the same that were found at Medline [16]. From the remaining, 8 were reviewed by full text and from these, 2 articles were included in our study ( see search design and assessment by selection criteria at appendix ).
The main characteristics of the studies used in our review (authors, journal of publication, publication year, country, sample size, follow up period, loss to follow up and kind of pain) are available in table 1.
Table 1. Main features of the studies included in the review.
Reference Publication
Publication year
Country
Sample
Size
Follow up
Period
(months)
Follow up losses
Kind of pain
Fransen, M. et al
[8]
Williams, R. et al
[10]
Andersson, H.
[11]
Gatchel, R. J. et
al [12]
Spine
Archives of PMR
European
JournalPain
Health
Psychology
2002
1998
2003
1995
Australia
USA
Sweden
USA
854
117
214
324
20
6
144
6
586
6
73
14
Klimiuk, P.S. et
al [13]
Spine 1987 UK 11 12 -------
Table 2 gives details of the main inclusion and exclusion criteria of the sample’s
Low back pain
Low back pain
Neckshoulder pain
Low back pain
Low back pain subjects. The studies were performed as standard cohorts.
617 of the initial 854 claimants of Fransen et al [8] study belonged to the target high risk occupational groups (nurse and nurse aids, heavy manual worker’s and drivers) and from these, 23.9% still receive compensation payments 3 months after the initial claim.
For the individual factors, increasing age, presence of a severe radiating pain in legs, a higher than normal body mass index and a Oswestry Disability Index (questionnaire that assesses general functional disability associated with back pain [14]) score indicating at least moderate disability were significant predictors of chronicity ( P <0.05) ( see also
Table 3 ).
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F ACULTY OF M EDIC INE
–
U N IVERS ITY OF P ORTO
Department of Biostatistics and Medical Informatics
Introdução à Medicina 2005/2006
Table 2. Inclusion and exclusion criteria of the sample’s subjects.
Reference
Fransen, M. et al
[8]
Williams, R. et al
[10]
Inclusion Criteria
• Nurses
• Nurses' aids
• Heavy manual workers
• Drivers
• Age between 15 and 18 years
• Back pain (T6 or below) that had been present "on a daily bases" from the previous
8 weeks as the only pain problem
Exclusion Criteria
• Taking medications known to affect mood
• Prior back surgery
• Pain secondary to neoplastic disease osteomyelitis, or fracture since the clinical course of these conditions differs from the "usual" back disorder
Andersson, H. [11]
Gatchel, R. J. et al
[12]
Klimiuk, P.S. et al
[13]
•
Neck/shoulder pain with or without reflexion in arms
•
Pain in at least 3 regions of arms/legs
•
Lumbar pain with duration inferior to 6 weeks
•
Presence of a first episode of acute low back pain and sciatica
•
Patients had no other active disease, with no evidence of ankylosing spondylitis as demonstrated by normal sacroiliac joints on radiography and the absence of tissue type
HLA B27
• In all subjects the ESR blood count, serum calcium, phosphate, and alkaline phosphatase levels are normal
•
Unemployed people
•
No patients had been exposed to any invasive procedure other than venepuncture within the previous 3 months
Those who showed low rates of insomnia, anxiety, social dysfunction and severe depression showed significant association with chronicity (see table 4) . Those with higher rates presented a high risk of developing chronicity. There were also found significant association with the perception that reporting to the Accident Rehabilitation and Compensation Insurance Corporation was discouraged; with unavailability of light duties on return to work, need to lift objects for at least ¾ of the working day, need to lift or manoeuvre heavy items regularly and need to spend at last ¾ of the day driving.
However, only the unavailability of light duties on return to work and the job requirement to lift for at least ¾ of the day were significant. The combination of more than one factor maintained the significance of each factor in the risk of developing chronicity. The most significant predictor was Oswestry Disability Index score above minimal disability: moderate disability, severe disability and very severe disability.
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F ACULTY OF M EDIC INE
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U N IVERS ITY OF P ORTO
Department of Biostatistics and Medical Informatics
Introdução à Medicina 2005/2006
Compared with scale norms for the Job Descriptive Index (90-item self-report questionnaire assesses six facets of job satisfaction: the work itself, present pay, opportunities of promotion, supervision, co-workers and overall satisfaction), participants in William et al.
study scored on average, below the 25 th
percentile on their satisfaction with the actual work they perform in their jobs. Their reports of satisfaction with supervisors and co-workers were, on average, between the 25 th
and 50 th
percentile.
Participants reported mild to moderate baseline pain, disability and distress, with considerable variability in their ratings. In contrast, 6-month pain ratings, disability and psychological distress were relatively mild overall; nevertheless, there continued to be a considerable range of pain, disability and distress.
To better understand the role that job satisfaction plays in the persistence of low back pain, it was examined the type of work performed by participants, both before and after the onset of pain. Type of work performed was classified as deskwork or working requiring light, moderate or heavy lifting. An estimate of social position (military rank) was also examined to see whether this explained the relation between job satisfaction and outcome.
Table 3. Individual characteristics of subjects that influence the evolution into chronic pain.
Reference
Fransen et al [8]
Studied factors
Increasing age (>46)
Severe radiating pain in legs
Normal body mass index
Higher than normal body mass index
Oswestry Disability score indicating minimal disability
OR (95%CI)
1.61 (1.05-2.47)*
2.3 (1.44-3.76)*
1.0*
1.85 (1.17-2.90)*
1.0*
Andersson, H
[11]
Oswestry disability score indicating moderate disability
3.48 (1.65-7.35)*
Oswestry disability score indicating severe disability 5.89 (2.84-12.20)*
Oswestry disability score indicating extreme disability 5.69 (2.73-11.89)*
Chilliness
Stiffness
Number of painful areas 1-3
Number of painful areas >3
1.73 (0.44-6.83)**
1.09 (0.35-3.40)**
3.34 (1.43-7.79)**
15.8 (4.53-55.3)**
Gatchel, R. et al
[12]
Race
Age
Pain and disability analogue
*Odds ratios (age- and gender-adjusted) for chronicity
** Adjusted odds ratio (no data on adjusting factors
0.207-1.152
0.925-1.818
1.307-2.007
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F ACULTY OF M EDIC INE
–
U N IVERS ITY OF P ORTO
Department of Biostatistics and Medical Informatics
Introdução à Medicina 2005/2006
Table 4. Psychosocial characteristics of subjects that influence the evolution into chronic pain.
Reference Studied factors
Somatic symptoms
Anxiety/insomnia
Social dysfunction
OR (95% CI)
1.31 (0.95-1.81)*
2.08 (1.50-2.89)*
2.79 (1.98-3.93)*
Fransen et al [8]
Severe depression
Job insatisfaction
New family member gained
Having a close friend outside the family
2.47 (1.66-3.67)*
1.14 (0.80-1.64)*
0.60 (0.39-0.91)*
0.44 (0.21-0.92)** Andersson, H
[11]
Gatchel, R. et al Axis II personality disorder
[12]
*Odds ratios (age- and gender-adjusted) for chronicity
0.874-4.415
** Adjusted odds ratio (no data on adjusting factors)
Table 5. Workplace factors that influence the evolution into chronic pain.
Reference Studied factors OR (95% CI)
Fransen et al [8]
Need to manoeuvre "extremely heavy" items regularly 1.48 (1.08-2.04)*
Need to spend, at least, 3/4 of the working day driving 1.82 (1.03-3.22)*
Unavailability of light duties on return to work
Lifting time for about half a day
1.99 (1.39-2.86)*
1.52 (1.01-2.24)*
Lifting time for about three fourths or more a day
Andersson, H
Work in a bent position
[11]
*Odds ratios (age- and gender-adjusted) for chronicity
** Adjusted odds ratio (no data on adjusting factors)
2.04 (1.41-2.96)*
5.31 (1.19-23.6)**
According to Klimiuk, P. S. et al [13], the persistence of mechanical damage and consequent chronicity of low back pain may be due to some factors such as surgery, prolapse of a disc, smoking and drugs (e.g. aspirin). Despite the important conclusions of this study, the methodology used was unusual. In fact, the variables used were continuous and no association measures were available.
To evaluate what array or combination of variables (age, sex, race, marital status, education, pain and disability analogue, Axis I depression, Axis I substance abuse, Axis
II personality disorder, and MMPI Scale) best differentiated between the two groups studied at Gatchel, R. et al [12], logistic regression analyses were applied. Only age and sex were found to significantly differentiate between the two groups.
All individuals participant in the Andersson, H.
[11] study showed an increased risk of developing chronic pain with the report of chilliness, stiffness, pain report at more than three areas and occurrence of bent positions at work ( see table 3 and 5 ). A decreased
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F ACULTY OF M EDIC INE
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U N IVERS ITY OF P ORTO
Department of Biostatistics and Medical Informatics
Introdução à Medicina 2005/2006 risk of developing chronic pain is showed when having a close friend outside the family.
Discussion
Results show that physical, psychological and work factors influence the evolution of acute pain into chronic pain. The physical ones, such as number of painful areas and severe and extreme Oswestry Disability, seem to have the greatest influence, which may be explained by the continued unpleasant experience they cause. These factors are increased by age, which is also an influence factor. Psychological and social factors are significant too, leading to chronicity when there is depression and social dysfunction.
However, sometimes, an aggressive modification on the daily routine such as the gain of a new family member or the beginning of a different job seems to reduce the risk of chronicity, possibly because it distracts the subject from the pain. Other modifications, such as financial crises or involvement in an accident seem to have the opposite effect.
Work conditions, especially when returning to work after absence because of an acute pain, play a very important role in developing chronicity. When there are no light duties on return to work and there is the need to lift objects for a great part of the working day, pain tends to persist. It would be highly recommendable that companies had special tasks for people recovering from acute pain. This might encourage people to return to work, reducing the company’s expenses with monetary compensation during inability. It would also be advisable that companies kept a psycho logician available for it’s employees, it might improve job satisfaction and reduce psychological factors that influence chronicity and, as 10 to 15% of the population suffer from it [2], it would be a good investment.
The present review was affected by various methodological and data limitations. On the one hand, the query definition, even though it was very inclusive and comprehensive, excluded some articles. On the other hand, the type of studies selected, cohort studies, are difficult to conduct. Longitudinal prospective studies give reliable data as they follow the participants while the causes play their role, but they lose a significant percentage of the initial sample through out the process, reducing the statistical
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F ACULTY OF M EDIC INE
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U N IVERS ITY OF P ORTO
Department of Biostatistics and Medical Informatics
Introdução à Medicina 2005/2006 significance of the conclusions. Studies including clinical trials are not ethically accepted in this domain. The heterogeneity verified among the sample’s population, the duration of the follow up and the factors studied reduced the possibility of aggregating the results.
Even though there are numerous articles concerning chronic pain and how it should be handled, very few refer to factors related to it. When factors are studied, they usually are accessed within the chronicity.
The results presented in this study agree with previous literature, supporting the evidence found for the influence of certain psychological factors in the progression to chronicity in Low Back Pain [15].
Although the effect on the transition was measured in standard deviation units, distress and depression was found to significantly predict chronicity especially in primary care.
Physical, psychological and workplace factors influence the evolution of acute pain into chronic pain, although the physical ones play the greatest influence. Further studies should be carried out, as this is an important issue with psychological, social and economic implications.
Acknowledgments
The authors acknowledge Dr. Luís Azevedo for assistance, counselling and comments on the draft manuscript. The authors would like to thank to Dr. Cristina Santos whom suggestions for the improvement of this article were very helpful. Finally, the authors are grateful to the Department of Biostatistics and Medical Informatics for the resources and to Professor Altamiro da Costa Pereira.
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F ACULTY OF M EDIC INE
–
U N IVERS ITY OF P ORTO
Department of Biostatistics and Medical Informatics
Introdução à Medicina 2005/2006
Appendix
Fluxogram of electronic search design and assessment protocol
Start
Bibliografic Research
Definition of Query
Medline: 376
Articles
Scopus: 505
Articles
Selected Articles 520
(361 in comum; 15 only in Medline;
144 only in Scopus)
Articles Revision by
Title and/or Abstract
Included or Excluded
(by applying exclusion criteria)?
Included
Remaining Articles
Revision by Full
Text
Included or Excluded
(by applying exclusion criteria)?
Included
Articles Included in the
Sistematic Review
5
Excluded
Excluded
Excluded Articles
443
Excluded Articles
72
End
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F ACULTY OF M EDIC INE
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U N IVERS ITY OF P ORTO
Department of Biostatistics and Medical Informatics
Introdução à Medicina 2005/2006
Articles assessment by application of exclusion criteria
Selected Articles n=520
(361 in comum; 15 only in Medline;
144 only in Scopus)
Articles Revision by
Title and/or Abstract n=520
Excluded Articles n=443
Reason for exclusion:
Articles nor in English nor in Portuguese n=75
Articles not related with the context of the review n=245
Not a cohort study n=54
Article that do not refer the evolution of acute pain into chronic n=69
Remaining Articles
Revision by Full Text n=77
Excluded Articles n=72
Reason for exclusion:
Articles not found in full text n=39
Articles not related with the context of the review n=9
Not a cohort study n=13
Article that do not refer the evolution of acute pain into chronic n=11
Articles Included in the
Sistematic Review n=5
13

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