1. Risk factors which influence the evolution of acute pain into chronic pain Systematic Review Class 6 Faculty of Medicine – University of Porto Department of Biostatistics and Medical Informatics

2. Introduction Pain Unpleasant sensory and emotional experience associated with actual or potential tissue damage [1]. Acute Pain & Chronic Pain Chronic pain is 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 [2]. It is estimated that between 10 and 15 % of the population suffers from chronic pain [2]. [1] Iasp-pain.org [Homepage on the internet]. IASP – International Association for the Study of Pain; [updated 2005 Oct 10; cited 2005 Dec 13]. Available from: http://www.iasp-pain.org/Iasp-pain.org [2] Smith BH, Hopton JL, Chambers WA. Chronic pain in primary care. Family Practice. 1999; 16: 475-482.

3. Objective To review systematically the literature regarding risk factors which influence the evolution of acute pain into chronic pain

4. Methods Inclusion criteria: Cohort studies that refer to the factors which influence the evolution of acute pain into chronic pain. Exclusion criteria: Language restriction: only studies in English or Portuguese would be included. Studies that are not connected with the context of our review. Studies that are not cohort studies. Studies that do not refer the evolution of acute pain into chronic.

5. Methods Query: “Chronicity AND Pain” Electronic databases used: Medline [16] (Nov 2005) Scopus [17] (Apr 2006) Articles obtained in the research: Medline – 376 articles Scopus – 505 articles (361 are included in Medline’s research) [16] Medline [database on the Internet]. National Library of Medicine (US); 2002 – [cited 2005 Nov]. Available from: http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?CMD=search&DB=pubmed [17] Scopus [database on the Internet]. New Jersey Institute of Technology (USA); [cited 2006 Mar]. Available from: http://www.scopus.com/scopus/home.url

6. Assessment Protocol (Medline) Organization of reviewer groups: 4 Reviewer Groups: three groups of 2 elements and one group of 3 elements Revision by abstract: All groups reviewed a sample of 6 articles Two groups with 93 articles and two groups with 92 articles Revision by full text: Three groups with 17 articles and one group with 18 articles

7. Assessment Protocol (Scopus) Organization of reviewer groups: 4 Reviewer Groups: three groups of 2 elements and one group of 3 elements Revision by abstract: Each reviewer group with 36 articles Revision by full text: Each reviewer group with 2 articles

8. Fluxogram

9. Articles Selection

10. Results Table 1 - Main features of the studies used in the review ReferencePublication year Country Sample Size Follow up Period (months) Follow up losses Kind of pain Francen, M. et al.Spine2002Australia85420586 Low back pain Williams, R. et al. Archives of PMR 1998USA11766 Low back pain Andersson, H. European JournalPain 2003Sweden21414473 Neck- shoulder pain Gatchel, R. J. Health Psychology 1995USA324614 Low back pain Klimiuk, P.S. et alSpine1987UK1112----- Low back pain

11. Table 2 - Inclusion and exclusion criteria of the sample’s subjects Results ReferenceInclusion CriteriaExclusion Criteria Fransen, M. et al [8] Nurses Nurses' aids Heavy manual workers Drivers Williams, R. et al [10] 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 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] Neck/shoulder pain with or without reflexion in arms Pain in at least 3 regions of arms/legs Gatchel, R. J. et al [12] Lumbar pain with duration inferior to 6 weeks Unemployed people Klimiuk, P.S. et al [13] 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 No patients had been exposed to any invasive procedure other than venepuncture within the previous 3 months

12. Results Table 3 – Individual characteristics of subjects that influence the evolution into chronic pain ReferenceStudied factorsOR (95%CI) Fransen et al [8] Increasing age (>46)1.61 (1.05-2.47)* Severe radiating pain in legs2.3 (1.44-3.76)* Normal body mass index1.0* Higher than normal body mass index1.85 (1.17-2.90)* Oswestry Disability score indicating minimal disability1.0* Oswestry disability score indicating moderate disability3.48 (1.65-7.35)* Oswestry disability score indicating severe disability5.89 (2.84-12.20)* Oswestry disability score indicating extreme disability5.69 (2.73-11.89)* Andersson, H [11] Chilliness1.73 (0.44-6.83)** Stiffness1.09 (0.35-3.40)** Number of painful areas 1-33.34 (1.43-7.79)** Number of painful areas >315.8 (4.53-55.3)** Gatchel, R. et al [12] Race0.207-1.152 Age0.925-1.818 Pain and disability analogue1.307-2.007 *Odds ratios (age- and gender-adjusted) for chronicity ** Adjusted odds ratio (no data on adjusting factors

13. Table 4 – Psychosocial characteristics of subjects that influence the evolution into chronic pain ReferenceStudied factorsOR (95% CI) Fransen et al [8] Somatic symptoms1.31 (0.95-1.81)* Anxiety/insomnia 2.08 (1.50-2.89)* Social dysfunction 2.79 (1.98-3.93)* Severe depression 2.47 (1.66-3.67)* Job insatisfaction 1.14 (0.80-1.64)* New family member gained0.60 (0.39-0.91)* Andersson, H [11]Having a close friend outside the family0.44 (0.21-0.92)** Gatchel, R. et al [12] Axis II personality disorder0.874-4.415 *Odds ratios (age- and gender-adjusted) for chronicity ** Adjusted odds ratio (no data on adjusting factors)

14. Table 5 –Workplace factors that influence the evolution into chronic pain ReferenceStudied factorsOR (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 1.99 (1.39-2.86)* Lifting time for about half a day 1.52 (1.01-2.24)* Lifting time for about three fourths or more a day2.04 (1.41-2.96)* Andersson, H [11] Work in a bent position 5.31 (1.19-23.6)** *Odds ratios (age- and gender-adjusted) for chronicity ** Adjusted odds ratio (no data on adjusting factors)

15. Discussion Relevant Results Physical, Psychological and Workplace factors influence the evolution of acute pain into chronic pain Physical factors play the greatest influence Number of painful areas >3 (OR 15.8) Oswestry disability score indicating severe disability (OR 5.9) Oswestry disability score indicating extreme disability (OR 5.7)

16. Discussion Relevant Results Aggressive modifications on daily routine that draw patients attention from pain reduce the risk of chronicity New family member gained (OR 0.6) Beginning of a different job (OR 0.7) Work conditions when returning to duties influence chronicity Unavailability of light duties on return to work (OR 1.9) Special tasks and psychological support for people recovering from acute pain might reduce company’s expenses with monetary compensation during inability and increase job satisfaction

17. Discussion Connection with existent literature The results presented 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] [15] Pincus T, Burton AK, Vogel S, Field AP. A Systematic Review of Psychological Factors as Predictors of Chronicity/Disability in Prospective Cohorts of Low Back Pain. Spine. 2002. Volume 27, number 5, pp E109-E120.

18. Discussion Methodological and Data limitations Query Definition Cohort Studies Longitudinal prospective studies give reliable data, as they follow the participants while the causes play their role However they lose a significant percentage of the initial sample, reducing the statistical significance of conclusions Heterogeneity The heterogeneity verified among the studies reduced the possibility of aggregating the results

19. Discussion Methodological and Data limitations Articles There are several studies concerning chronic pain and how it should be handled, but few about factors that promote chronicity When factors are studied, they are usually acessed whithin chronicity Further studies should be carried out, as this is an important issue with psychological, social and economic implications

20. Discussion Conclusions Physical, Psychological and Workplace factors influence the evolution of acute pain into chronic pain Physical factors play the greatest influence Further studies should be carried out

21. References [1] Iasp-pain.org [Homepage on the internet]. IASP – International Association for the Study of Pain; [updated 2005 Oct 10; cited 2005 Dec 13]. Available from: http://www.iasp-pain.org/Iasp-pain.org [2] Smith BH, Hopton JL, Chambers WA. Chronic pain in primary care. Family Practice. 1999; 16: 475-482. [3] Purves AM, Penny K, Munro C. Defining chronic pain for epidemiological research – acessing a subjective definition. The Pain Clinic. 1998; 10: 139- 147. [4] IASP – Pain Clinical Updates; volume XI, No. 2; June 2003 [5] Von Korff M, Dworkin SF, Le Resche L. Graded chronic pain status: an epidemiologic evaluation. Pain. 1990; 40: 279-291. [6] Bowsher D, Rigge M, Sopp L. Prevalence of chronic pain in the British population: a telephone survey of 1037 households. The Pain Clinic. 1991; 4: 223-230. [7] Brattberg G, Thorslund M, Wilkman A. The prevalence of pain in the general population. The results of a postal survey in a county in Sweden. Pain. 1989; 37: 215-222. [8] Fransen M, Woodward M, Norton R, Coggan C, Dawe M, Sheridan N. Risk Factors Associated with the Transition From Acute to Chronic Occupational Back Pain. Spine. 2002; 27(1): 92-98. [9] Pai M, McCulloch M, Gorman JD, Pai N, Enanoria W, Kennedy G et al. Systematic reviews and meta-analyses: An illustrated, step-by-step guide. The National Medical Journal of India. 2004; 17(2): 86-95. [10] Williams RA, Pruitt SD, Doctor JN, Epping-Jordan JE, Wahlgren DR, Grant I, et al. The contribution of job satisfaction to the transition from acute to chronic low back pain. Archives of physical medicine and rehabilitation. 1998 April; 79: 366-374. [11] Andersson H. The course of a non-malignant chronic pain: a 12-year follow-up of a cohort from the general population. European Journal of Pain. 2004; 8: 47-53. [12] Gatchel RJ, Polatin PB, Kinney RK. Predicting outcome of chronic back pain using clinical predictors of psychopathology: a prospective analysis. Health Psychol. 1995 Sep; 14(5): 415-20. [13] Klimiuk PS, Pountain GD, Keegan AL, Jayson MI. Serial measurements of fibrinolytic activity in acute low back pain and sciatica. Spine. 1987 Nov;12(9): 925-8. [14] Fairbanks JC, Coouper J, Davies JB, et al. The Oswetry Low Back Pain Disability Questionnaire. Physioteherapy 1980; 66:271-3 [15] Pincus T, Burton AK, Vogel S, Field AP. A Systematic Review of Psychological Factors as Predictors of Chronicity/Disability in Prospective Cohorts of Low Back Pain. Spine. 2002; Volume 27, number 5, pp E109-E120. [16] Medline [database on the Internet]. National Library of Medicine (US); 2002 – [cited 2005 Nov]. Available from: http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?CMD=search&DB=pubmed [17] Scopus [database on the Internet]. New Jersey Institute of Technology (USA); [cited 2006 Mar]. Available from: http://www.scopus.com/scopus/home.url