Prevalence of Chronic Pain: Systematic review

1. Prevalence of Chronic Pain: Systematic review Introduction to Medicine

2. Prevalence of Chronic Pain: Systematic review Introduction to Medicine This systematic review is part of a research project for the Introduction to Medicine subject, of BiostatisticalService in the Medicine Faculty of Oporto University

3. Prevalence of Chronic Pain: Systematic review • In this work we will focus: • Title and keywords • Introduction • Participants • Methods • Results • Discussion • Acknowledgements • References • Authors Introduction to Medicine

4. Prevalence of Chronic Pain: Systematic review 1. Title and keywords Introduction to Medicine Prevalence of Chronic Pain in the General Population Keywords: Prevalence, Chronic pain, Systematic review, General population

5. Prevalence of Chronic Pain: Systematic review 2. Introduction Introduction to Medicine • Chronic pain: definition • Pain definition: “(...)an unpleasant sensory and emotional experience associated with actual and potential tissue damage, or described in terms of such damage (...)” ([15]) • Chronic pain definition:“pain without apparent biological value that has persisted beyond the normal tissue healing time, usually taken to be 3 months” ([15])

6. Prevalence of Chronic Pain: Systematic review 2. Introduction Introduction to Medicine Definitions of Pain – Historical References • 16th century – Descartes developed the Specificity Theory • Intensity of pain is directly related with the amount of tissue injury • After Descartes – a lot of theories appeared

7. Prevalence of Chronic Pain: Systematic review 2. Introduction Introduction to Medicine • Most accepted theory – “Gate Control” • Ronald Melzack and Patrick Wall; • Existance of “gates” that close or open depending on different variables; • The “Gates” open - pain messages run easily and the pain has a huge intensity; • The “Gates” close – pain is not experienced because the messages don’t cross the “gates”; • However, no one has yet understood or explained the mechanisms that are behind the pain process and how it is controlled.

8. Prevalence of Chronic Pain: Systematic review 2. Introduction • Definition of pain and chronic pain – Associated Problems: • Incapacity in quantifying pain; • Subjective nature; • Contextualization; • No agreement about the necessary time to consider chronic pain (1 month, 3 months or 6 months beyond a normal recovery period). Introduction to Medicine

9. Prevalence of Chronic Pain: Systematic review 2. Introduction Introduction to Medicine • Systematic review: definition • Planned review to answer a specific question and that uses systematic and explicit methods to identify, select and evaluate the studies; • It consists in reviewing all the existent references in medicine databases: Scopus; Pubmed (for example). TOP

10. Prevalence of Chronic Pain: Systematic review 2. Introduction Introduction to Medicine • Relevance of the question and comments • Chronic pain: • Has an impact in patients’ quality of life, in family, health workers and institutions related to them and in society in general.1 1- Pain Association’s International Network (P.A.I.N.)

11. Prevalence of Chronic Pain: Systematic review 2. Introduction Introduction to Medicine • Objectives • Quantify the prevalence of chronic pain in general population; • Relate chronic pain with variables such as geographical regions, anatomical areas, age, gender, ...; • Determine the most common definition of chronicity.

12. Prevalence of Chronic Pain: Systematic review 3. Participants Introduction to Medicine • Study design – systematic review • Selection criteria • Inclusion criteria: • Articles should be published in an indexed scientific journal ; • Focus chronic pain (or its synonyms such as “continuous pain”, “delayed pain” and “intolerable pain”); • Cross-sectional studies (study of prevalence); • Studies with participants 18 years old or above;

13. Prevalence of Chronic Pain: Systematic review 3. Participants Introduction to Medicine • Exclusion criteria: • Studies focusing acute pain or other kind of pain; • Studies related to children/teenagers (<18); • Studies only comparing chronic pain with another type of pain; • Studies with animals; • Language not mastered.

14. Prevalence of Chronic Pain: Systematic review 4. Methods • Search strategy in a systematic review: • Query Formulation: • Pubmed • Pain – 308765 • Pain AND prevalence – 27569 • Pain AND prevalence AND chronic - 3966 • “chronic pain” AND prevalence – 840 • Scopus • “chronic pain” AND prevalence – 536 • Endnote (References management software) • 1137 (239 repeated articles) Introduction to Medicine Total: 1376

15. Prevalence of Chronic Pain: Systematic review 4. Methods • Articles selection • 1st phase or screenphase – reading the title and abstract of the obtained articles in the databases and exclusion of the ones that do not fit. • 5 random groups of 2 people; • 2nd phase or inclusion phase – according with the pre-established criteria of inclusion and exclusion, the fitting articles were chosen • the groups were maintained. Introduction to Medicine

21. Prevalence of Chronic Pain: Systematic review 5. Results Introduction to Medicine • The articles information was extracted with the help of the following table:

22. Prevalence of Chronic Pain: Systematic review 5. Results • General Characteristics • Articles since 1996 to 2005; • Geographical distribution; Introduction to Medicine

23. Prevalence of Chronic Pain: Systematic review 5. Results General Characteristics Introduction to Medicine

24. Prevalence of Chronic Pain: Systematic review 5. Results Introduction to Medicine • General/specific chronic pain

25. Prevalence of Chronic Pain: Systematic review 5. Results Introduction to Medicine • Anatomical distribution

26. Prevalence of Chronic Pain: Systematic review 5. Results Introduction to Medicine • Survey method

27. Prevalence of Chronic Pain: Systematic review 5. Results • Response rate • Minimum – 23,80% • Maximum – 95,50% • Median - 59,00% Introduction to Medicine

28. Prevalence of Chronic Pain: Systematic review 5. Results • Response rate Introduction to Medicine

29. Prevalence of Chronic Pain: Systematic review 5. Results Introduction to Medicine • Number of participants • Minimum – 77 • Maximum – 131535

30. Prevalence of Chronic Pain: Systematic review 5. Results • Number of participants Introduction to Medicine

31. Prevalence of Chronic Pain: Systematic review 5. Results • Definitions of Chronic Pain • Chronicity (time needed so that acute pain becomes chronic pain) Introduction to Medicine

32. Prevalence of Chronic Pain: Systematic review 5. Results Introduction to Medicine • Definitions of Chronic Pain • Intensity • Defined in six articles ([2], [4], [11], [13], [14], [17]). • Two articles defined the same scale of intensity ([2], [13]): • Grade I: low disability – low intensity; • Grade II: low disability – high intensity; • Grade III: high disability – moderately limiting; • Grade IV: high disability – severely limiting. • Two of the articles used numeric scales ([17] defined a 0-10 scale and [11] defined a 0-6 scale). • The other two articles defined a nominal scale with two variables.

33. Prevalence of Chronic Pain: Systematic review 5. Results Introduction to Medicine • Consequences • Consequences of chronic pain were defined in nine articles ([3], [4], [7], [8], [13], [14], [17], [18] and [24]). • To define the grade of consequences of “chronic pain”, [17] defined a 0-10 scale. • The remaining articles mentioned that the main consequences were interference in work, depression, anxiety, distress, sleep disturbances and great disability.

34. Prevalence of Chronic Pain: Systematic review 5. Results Introduction to Medicine • Prevalence of Chronic Pain • Minimum – 0,79% • Maximum – 83,90% • Median – 19,00%

35. Prevalence of Chronic Pain: Systematic review 5. Results Introduction to Medicine

36. Prevalence of Chronic Pain: Systematic review 5. Results • Prevalence concerning anatomical regions Introduction to Medicine Neck and/or Head Pain – 23,80%; Chest Pain – 5,90%; Upper Limb Pain – 20,23%; Abdomen Pain – 7,45%; Lower Limb Pain – 25,88%; Back Pain – 41,63%; Musculoskeletal Pain – 35,95%; The differences between the different locations of chronic pain concerning its prevalence are not statistically significant (Kruskall-Wallis test).

37. Prevalence of Chronic Pain: Systematic review 5. Results • Prevalence concerning geographical areas Introduction to Medicine Note: The number in brackets refers to the number of articles which mentioned the prevalence

38. Prevalence of Chronic Pain: Systematic review 5. Results Introduction to Medicine • Patient characteristics • Gender • Eleven studies ([2], [3], [5], [8], [9], [14], [18], [19], [20], [21], [24]) referred the prevalence in the different genders. • [14] (the part about the USA) refers the prevalence only in the female gender; [18] refers the prevalence only in the male gender. • Male gender: • Median – 19,95% • Minimum – 14,80% • Maximum – 75,00% • Female gender: • Median – 22,55% • Minimum – 20,00% • Maximum – 31,40%

39. Prevalence of Chronic Pain: Systematic review 5. Results Introduction to Medicine

40. Prevalence of Chronic Pain: Systematic review 5. Results Introduction to Medicine

41. Prevalence of Chronic Pain: Systematic review 5. Results Introduction to Medicine • Age groups • Thirteen articles ([2], [3], [4], [5], [7], [8], [9], [11], [14], [19], [20], [21], [24]) referred the prevalence in different age groups. • Social components • Eight articles ([3], [5], [7], [8], [9], [17], [20] and [24]) associate chronic pain with social components. • No associations were made with the prevalence of chronic pain.

42. Prevalence of Chronic Pain: Systematic review 5. Results Introduction to Medicine • Quality Evaluation • The quality evaluation of the data having into account the following criteria: • Number of participants; • Definition of chronicity; • Specificity of pain; • Gradation; • Intensity; • Response rate; • Survey method; • Type of questionnaire; • Setting; • Socio-demographic characteristics.

43. Prevalence of Chronic Pain: Systematic review 6. Discussion • The discussion was made taking into account the quality evaluation • The main point focused were: • Response Rate; • Number of participants; • Definition of chronic pain; • Prevalence; • Anatomical regions; • Socio-demographic characteristics; • Intensity; • Consequences; • Critical comparison with other studies; • Limitations. Introduction to Medicine

44. Prevalence of Chronic Pain: Systematic review 6. Discussion Introduction to Medicine • Response Rate • The median response rate obtained was relatively high. • The bigger the response rate, more quality was given to the study that was being analyzed. • It seemed to be more correct to use standardized questionnaires such as telephone and postal questionnaires, but a larger response rate was obtained in the non-standardized ones. In order to evaluate this variable, the response rate was compared with each type of questionnaire.

45. Prevalence of Chronic Pain: Systematic review 6. Discussion Introduction to Medicine • Number of participants • A higher importance was given to the articles that mentioned a significative number of participants. • Note: This last variable is very close to the response rate and to the type of questionnaire so that this study tried to evaluate them as a whole.

46. Prevalence of Chronic Pain: Systematic review 6. Discussion Introduction to Medicine • Definition of Chronic Pain • The majority of articles used a 3 months definition; • the criteria of this study further focusing the presence of a specific value such as 3 or 6 months, giving less importance to the articles that failed to mention the chronicity. • More importance was given to the articles that focused general chronic pain and to those that referred the socio-demographic characteristics. • Chronicity • Most of the articles, 64,71%, considered that the pain persistence was 3 months, similar to the definition of chronic pain that was initially established in this study (based on [15]), whilst 23,53% considered it to be 6 months; 11,76% did not mention.

47. Prevalence of Chronic Pain: Systematic review 6. Discussion Introduction to Medicine • Prevalence of chronic pain • It was found great heterogeneity among the articles; • The maximum prevalence: 83,90% [16] in a USA sample. Because of the fact that it is possible that the sample was rendered less than fully representative and the questionnaire was not validated; • The minimum prevalence: 0,79% [11] in Holland • Confined to unexplained pain, and not all chronic pain. • Inclusion criteria focused the attention on very severe chronic pain patients, in contrast to other studies where patients are often troubled by pain. • Defined chronicity as more than 6 months.

48. Prevalence of Chronic Pain: Systematic review 6. Discussion Introduction to Medicine • Anatomical Region • The statistical data was not considered significant; • It was concluded that the highest prevalence occurred in back pain and musculoskeletal pain; • The lowest prevalence was related to abdominal pain and chest pain. • Age • It was concluded that there is a close relation between chronic pain and age; • Despite the insufficiency of data, the prevalence of chronic pain seems to increase with ageing.

49. Prevalence of Chronic Pain: Systematic review 6. Discussion Introduction to Medicine • Geographical area • The absence of information about developing countries limited the study conclusions. • There were only discussed the countries that had more than one article;

50. Prevalence of Chronic Pain: Systematic review 6. Discussion Introduction to Medicine • The upper value found was in USA: 51,45% • From the data quality evaluation, it was concluded that the article [14] had to be given more importance than to the article [16] due to the fact that it contained a more significant sample. • Norway : 24,40% • It has two articles, [18] and [19], which had the same definition of chronic pain and obtained de same prevalence having also the same number of participants (4000). It is important to mention that both articles were made in 2004 by the same author.