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  1. Faculdade de Medicina da Universidade do Porto(Medicine College of Oporto University)Introduction to Medicine Prevalence of chronic pain in adult general population within Oporto area Workgroup by class 17 School Year 2006/ 2007

  2. Faculdade de Medicina da Universidade do Porto(Faculty of Medicine of Oporto)Introduction to Medicine1st School Year Annual assignment Subject’s Main Teacher: Altamiro Costa Pereira, MD, PhD Instructor: Luis Azevedo, MD

  3. Introduction 1. Research question What is chronic pain (CP) prevalence in adult general population within Oporto area? 1.1 Context of question Chronic pain is a contemporaneous issue. According to Tulder (1995, referred by Chrubasik et al [1]) we can even say, that “Chronic pain is a burden to individuals and a challenge to society.”. Therefore, this study expects to be an interesting and attractive way of learning about this matter. [1] Chrubasik S, Junck H, Zappe HA, Stutzke O. European Journal of Anaesthesiology. 1998.

  4. Introduction First challenge seems to be the very definition of chronic pain. Literature studied shows that there is no established pattern about this subject. Basically, International Association for the Study of Pain (IASP) [3] defines pain as: “ An unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage.” Which defines the subjective character of the definition to any kind of pain. [3] Harstall C, Ospina M. Pain Clinical Updates. 2003. Available from:

  5. Introduction Murray [2] says that: “Chronic pain is an important and social problem for three major reasons. It is distressing to patients, as it alters their lives and sometimes their employment, and it responds poorly to treatment. Chronic pain is a common condition that has huge financial costs to society. Finally, despites its frequency and large costs, it is difficult to understand and manage, and eventually becomes a source of stress and misunderstanding to all concerned”. [2] Murray OC. Available from :

  6. Introduction And more precisely, “The International Association for the Study of Pain (IASP) provides a widely used definition of CP that takes into account duration and “appropriateness”. IASP defines CP as pain without apparent biological value that has persisted beyond the normal tissue healing time (usually taken to be 3 months).”[3] Thus, accordingly to the definition of IASP and studied literature of CP, we can accept in practice for this study an endurance further than 3 months. [3] Harstall C, Ospina M. Pain Clinical Updates. 2003. Available from:

  7. Introduction 2. Primarygoal Estimate the period prevalence of chronic pain in adult general population within Oporto area. Specifically, for this study, it will be considered as a primary objective the estimate of the period prevalence of CP in general adult population of Oporto1 area. This is, the prevalence of CP in the last year (referring to the date of the answer). 1This region includes the following councils: Arouca, Espinho, Gondomar, Maia, Matosinhos, Oliveira de Azeméis, Ovar, Paredes, Porto, Póvoa de Varzim, Sta. Maria da Feira, Sto. Tirso, São João da Madeira, Trofa, Vale de Cambra, Valongo, Vila do Conde and Vila Nova de Gaia. Defined, using the call list: Oporto area and South of the Douro. [3] Harstall C, Ospina M. Pain Clinical Updates. 2003. Available from:

  8. Introduction 2.1. Context of primary goal “Yet access to reliable data on prevalence – the proportion of a defined population that has CP at some specified time – is an important prerequisite for efficient planning of health services. Understanding factors that underlie variation in prevalence estimates of CP can advance our understanding of its public health impact.” [3]

  9. Introduction 3. Secondary goals 3.1. Estimate prevalence of CP relatively to sex; 3.2. Relate prevalence of chronic pain with age; 3.3. Estimate location of pain; 3.4. Find potential causes/origins of pain; 3.5. Scale grade of pain (without loss due to subjectivity); 3.6. Register in which ways chronic pain interferes the subject’s familiar and social life; 3.7. Estimate the number of individuals with clinical confirmation of chronic pain;

  10. Methods 1. Study design “Cross sectional studies: These are primarily used to determine prevalence. Prevalence equals the number of cases in a population at a given point in time. All the measurements on each person are made at one point in time.”[4] Like Newman [et al] [5] says, in a cross-sectional study the investigator makes all measurements on a single occasion, there is no follow up period. And in fact, the cross sectional design is the only one that gives the prevalence of a disease or risk factor. [4] Mann, CJ. Emergency Medicine Journal. 2003. Available from: [5] Newman TB, Warren SB, Steven RC, Stephen BH. In Designing Clinical Research.

  11. Methods Table 1: adapted of [4] [4] Mann, CJ. Emergency Medicine Journal. 2003. Available from:

  12. Methods As key points we would like to distinguish: “The most important advantage of cross sectional studies is that in general they are quick and cheap. As there is no follow up, less resources are required to run the study. Cross sectional studies are the best way to determine prevalence and are useful at identifying associations that can then be more rigorously studied using a cohort study or randomized controlled study. The most important problem with this type of study is differentiating cause and effect from simple association.” [4] [4] Mann, CJ. Emergency Medicine Journal. 2003. Available from:

  13. Methods 2. Sample dimension Sample dimension, will be determine in function of the appropriate calculation of algorithm to permit describe confidence intervals for proportions with error margin of 7 %, for a level of confidence of 95%. Allowing for an anticipated failure to respond of about 50%, the sample size defined includes 400 individuals.

  14. Methods 3. Data collection In order to achieve answers for primary and secondary goals, data collection of this study will describe the followings steps: - Send on a postal questionnaire to 400 individuals, residents within Oporto area, registered in Phone book “Região do Porto e Sul do Douro; - The questionnaires, have been sent in 30th March of 2007; - To improve response rates, it will be send a second correspondence to the 400 individuals after 2 weeks: 16th April of 2007.

  15. Methods • 4. Sample selection • According to precedent references it will be used the Phone book “Região do Porto e Sul do Douro”. Specifically, relation with this “data register”, it will be important to point some practical aspects: • - It is a register of simple use and easy access; • - However, the sample is reduced to the residents within Oporto area, registered in Phone book “Região do Porto e Sul do Douro.The signatures can be on behalf of an already deceased individual or a person that has changed of habitation;

  16. Methods On the other hand, the questionnaire is not applicable to illiterate individuals, or those with difficult to understanding questions. Therefore, it is not an immediate method, once it is dependent of the fulfillment of the services: CTT.

  17. Methods SuperCool Random Number Generator This software facilitates our sampling selection: Sample randomized in groups. Through the indication of the behind described interval, this software will randomly generate the numbers corresponding to page, column and line; where we will find the address of the participants. It guarantees a randomly choice (on age, sex and other social-demographic aspects). But, in the other hand,the software does not guarantee a valid address with the combination page/ column / line. To resolve this limitation, it was created a Standard Operation Procedures.

  18. Methods 4.1. Selection of participants - drawing Random draw of: - page: [89 , 1429] , x E |N - column: [1 , 4] , x E |N - line: [1 , 133] , x E |N For the Phone book “Região do Porto e Sul do Douro” Using the software program: SuperCool Random Number Generator 1.04

  19. Methods 5. Pilot study After selection of 20 addresses, using the software: SuperCool Random Number Generator1.04, it was sent a pre-test questionnaire. In this pre-test, we tried to improve our questionnaire, finding some difficulties in the answers people would gave us. Sent on 5th February 2007. Deadline of reception: 19th February 2007.

  20. Methods 20 Questionnaires sent 5 Returned with address unknown 1 questionnaire returned With a very low response rate, our objectives in this pre-test haven’t been fulfilled. So, we started applying our questionnaire on the streets to any person who were available to spend a couple of minutes.

  21. Methods Main conclusions: We noticed that our questionnaire needed some changes: - creation of a new question asking the sex; - creation of a new question asking for medical conformation of chronic pain; - ask age instead of birth date; - need to change some vocabulary.

  22. Results 1. Response rate 400 Questionnaires sent 52 Returned with address unknown 62 questionnaire returned A total of 62 questionnaires were returned after the two mailings, which represents a response rate of 17,82%.

  23. Results

  24. Frequency Percent 18 - 44 21 33.9% 45 - 64 23 37.1% >= 65 16 25.8% Missing 2 3..2% Total 62 100% Results 2. Characteristics of the total sample Minimum: 19 years Maximum: 85 years AGE Frequency Percent Female 34 54.8% Male 26 41.9% SEX Missing 2 3.2% Total 62 100%

  25. Results Frequency Percent MARITAL STATUS Single 14 22.6% Separeted or divorced 4 6.5% Married 36 58.1% Widow 6 9.7% * 2 missing Total 60* 100%

  26. Frequency Percent without schooling 2 3.2% Primary school 16 25.8% Elementary school 5 8.3% Secundary school 20 33.3% University 17 28.2% Missing 2 3.2% Total 62 100% Results EDUCATIONAL STATUS

  27. Frequency Percent Valid Percent Full-time 14 22,6 23,7 Part-time 2 3,2 3,4 Housewives 9 14,5 15,3 Liberals 6 9,7 10,2 Student 8 12,9 13,6 Pensioned 2 3,2 3,4 Unemployed (looking for 1st Job) 16 25,8 27,1 Other 2 3,2 3,4 Total 59 95,2 100,0 Missing 3 4,8 Total 62 100,0 Results EMPLOYMENT STATUS

  28. Results 3. People with Pain We noticed 49,2% of the homes that answered to our questionnaire reported the presence of at least one person with Chronic Pain (pain of > 3 months duration). CI 95% for mean [36,3 ; 62,1]

  29. Frequency Percent Valid Percent Cumulative Percent 66,7 Valid Without CP 40 64,5 66,7 100,0 With CP (> 3 meses) 20 32,3 33,3 Total 60 96,8 100,0 Missing Non response 2 3,2 Total 62 100,0 Results - The prevalence of chronic pain in our sample is 33,3% with a CI 95% [21,1 ; 45,6].

  30. Results - Prevalence of chronic pain has higher values in female than in male, despite the fact that their confidence intervals coincide in some values.

  31. Results

  32. Results - Participants have been divided into three age groups in order to help us to understand the relation between age and CP.

  33. Results - Duration of Pain – here we tried to understand the period of pain that our participants have experienced.

  34. Median Minimum Maximum Interquartil Range Intensity Maximum 6 2 10 2 Mean 6 1 10 1 Results - Pain intensity – participants were told to describe the pain intensity using a 0-10 scale. - Interference in welfare – we can see that chronic pain has an interference in people’s feelings. We used a 0-5 scale. Median Minimum Maximum Interquartile Range Sad/Depressed 4 0 5 2 Nervous/Ansious 4 1 5 2 Angry 3 0 5 3 Lonely/Isolated 3 0 5 4 Incapable joy life 4 0 5 2

  35. Median Minimum Maximum Interquartile Range Ample capacity 6 3 10 3 Mood 6 0 10 3 Ability to walk 6 3 10 3 Normal work 7 3 10 4 Relationship with other persons 3 0 10 6 Sleep 7 0 10 6 Life Pleasure 6 0 10 5 Results - Interference in general life – here, we used a 0-10 scale in order to understand how chronic pain can limit the normal activity of people’s life.

  36. Results - We selected the questionnaires of the people who have pain and tried to understand the very nature of the pain.

  37. Results - Pain’s location – we present here the ranking of the locations proposed to our participants..

  38. Results - Pain’s location 9 6 12 7

  39. Results - Causes / Origins of pain – Each participant could mention more than one disease. The main problems/diseases our participants reported were: 1. Spinal Column – 10/20 participants 2. Arthritis – 9/20 participants 3. Headaches – 4/20 participants 4. Surgical procedures – 4/20 participants

  40. Results - Medically confirmed pain

  41. Results - Professional Interference – working days lost due to pain in the last 6 months. 15 participants answered, 5 participants did not.

  42. Results - Participants were instructed to report their medication and/or treatment.

  43. Results - We asked participants to report, using a 0-100 scale, their relief in the last 6 months with treatment.

  44. Results - Professional attendance – we wanted to know how many participants are followed-up by any health professional and the most solicited ones.

  45. Conclusion / Discussion • According to our study, 33.3% of the respondents reported pain of ≥3 month’s duration (chronic pain); • The prevalence of chronic pain is higher in female than in male; • Most individuals described high values for their pain intensity and for interference of pain in social life (but the results not permit us a sustainable conclusion because is a very subjective issue); • Almost 25% of the study participants had experienced chronic pain for over 10 years.

  46. Table: Comparative description of the characteristics of 13 studies on chronic pain [3] Harstall C, Ospina M. Pain Clinical Updates. 2003. Available from:

  47. References [1] Chrubasik S, Junck H, Zappe HA, Stutzke O. A survey on pain complaints and health care utilization in a German population sample. European Journal of Anaesthesiology. 1998; 15: 397- 408. [2] Murray OC. Chronic pain. [monograph on the Internet].Workers Compensation Board of Nova Scotia. Available from : [3] Harstall C, Ospina M. How Prevalent is Chronic Pain? Pain Clinical Updates. 2003 Jun; Vol. XI, 2. Available from: [4] Mann, CJ. Observational research methods. Research design II: cohort, cross sectional, and case-control studies. Emergency Medicine Journal. 2003; 20: 54-60. Available from: [5]Newman TB, Warren SB, Steven RC, Stephen BH. Designing an Observational Study: Cross-sectional and Case-control Studies. In Designing Clinical Research. P.107. [6] Verhaak PFM, Kerssens JJ, Dekker J, Marjolijn JS, Bensing JM. Prevalence of chronic benign pain disorder among adults: a review of the literature. Pain. 1998; 77: 231-9. [7] Smith BH, Penny KI, Purves AM, Munro C, Wilson B, Grimshaw J, et al. The Chronic Pain Grade questionnaire: validation and reliability in postal research. Pain.1997; 71: 141-7.

  48. References [8] Elliot MA, Smith BH, Penny KI, Smith WC, Chambers WA. The epidemiology of chronic pain in the community. The Lancet. 1999; 354: 1248-52. [9] Andersson GBJ. Epidemiological features of chronic low-back pain. The Lancet. 1999; 354: 581-85. [10] Rustoen T, Wahl AK, Hanestad BR, Lerdal A, Paul S, Miaskowski C. Prevalence and characteristics of chronic pain in the general Norwegian population. European Journal of Pain. 2004; 8: 555-565. [11] Blyth FM, March LM, Cousins MJ. Chronic pain-related disability and use of analgesia and health services in a Sidney community. MJA. 2003; 179: 84-7. [12] Català E, Reig E, Artés M, Aliaga L, López JS, Segú JL. Prevalence of pain in the Spanish population: telephone survey in 5000 homes. European Journal of Pain. 2002; 6: 133-140. [13] Mallen C, Peat G, Thomas E, Croft P. Severely disabling chronic pain in young adults: prevalence from a population-based survey in North Staffordshire. BMC musculoskeletal Disorders. 2005; 6: 42. [14] Ruehlman LS, Karoly P, Newton C, Aiken LS. The development and preliminary validation of the Profile of Chronic Pain: Extended Assessment Battery. Pain. 2005; 118: 380-9.

  49. Acknowledgements Subject’s Main Teacher: Altamiro Costa Pereira, MD, PhD Instructor: Luis Azevedo, MD