Workgroup by class 17

Prevalence of chronic pain in adult general

population within Oporto area

School Year 2006/ 2007

Faculdade de Medicina da Universidade do Porto(Medicine College of Oporto University)

Introduction to Medicine

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

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.

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: http://www.iasp-pain.org/terms-

p.html#Pain.

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 : http://www.wcb.ns.ca/chronicpain.pdf.

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.

Introduction

[3] Harstall C, Ospina M. Pain Clinical Updates. 2003. Available from: http://www.iasp-pain.org/terms-

p.html#Pain.

2. Primary goal

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).

1 This 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.

Introduction

[3] Harstall C, Ospina M. Pain Clinical Updates. 2003. Available from: http://www.iasp-pain.org/terms-

p.html#Pain.

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]

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;

Introduction

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: emj.bmjjournals.com.

[5] Newman TB, Warren SB, Steven RC, Stephen BH. In Designing Clinical Research.

Methods

Objective Common design

Prevalence Cross sectional

Incidence Cohort

Cause (in order of reliability)

Cohort, case-control, cross sectional

Prognosis Cohort

Treatment effect Controlled trial

Table 1: adapted of [4]

[4] Mann, CJ. Emergency Medicine Journal. 2003. Available from: emj.bmjjournals.com.

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:

emj.bmjjournals.com.

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.

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.

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;

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.

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.

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

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.

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.

Methods

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.

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%.

Results

Citizens Randomly drawn from the

phone bookN=400

52 returned with addresss unknownN=348

Returned questionnaireN=62

Response rate:62/ 348=17,82%

Participants not in Chronic

PainN=35

Participants who reported generally

having pain N=25

Missing responses to the question related

with having painN=2

Participants in pain ≥3 months

durationN=20

Participants in pain <3 months

durationN=3

Praticipants that did not know pain’s

durationN=1

Participants that did not answer

(missing)N=1

Results

2. Characteristics of the total sample

100%62Total

3..2%2Missing

25.8%16>= 65

37.1%2345 - 64

33.9%2118 - 44

PercentFrequency

Minimum: 19 years

Maximum: 85 years

100%62Total

3.2%2Missing

41.9%26Male

54.8%34Female

PercentFrequency

AGE

SEX

Results

MARITAL STATUS

100%60*Total

9.7%6Widow

58.1%36Married

6.5%4Separeted or divorced

22.6%14Single

PercentFrequency

* 2 missing

Results

EDUCATIONAL STATUS

100%62Total

3.2%2Missing

28.2%17University

33.3%20Secundary school

8.3%5Elementary school

25.8%16Primary school

3.2%2without schooling

PercentFrequency

Results

EMPLOYMENT STATUS

100,062Total

4,83Missing

100,095,259Total

3,43,22Other

27,125,816Unemployed (looking for 1st Job)

3,43,22Pensioned

13,612,98Student

10,29,76Liberals

15,314,59Housewives

3,43,22Part-time

23,722,614Full-time

Valid PercentPercentFrequency

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]

Results

- The prevalence of chronic pain in our sample is 33,3% with a CI

95% [21,1 ; 45,6].

100,062Total

3,22Non responseMissing

100,096,860Total

100,0

33,332,320

With CP(> 3 meses)

66,7

66,764,540

Without CPValid

Cumulative PercentValid PercentPercentFrequency

Results

- Prevalence of chronic pain has higher values in female than in

male, despite the fact that their confidence intervals coincide in some values.

SexStatisti

c

Chronic Pain

Female

Proportion 0,4194

CI 95% for mean

Lower Bound 0,2354

Upper Bound 0,6033

Male

Proportion 0,1923

CI 95% for mean

Lower Bound 0,0300

Upper Bound 0,3546

Results

Crosstab

18 14 32

56,3% 43,8% 100,0%

46,2% 73,7% 55,2%

21 5 26

80,8% 19,2% 100,0%

53,8% 26,3% 44,8%

39 19 58

67,2% 32,8% 100,0%

100,0% 100,0% 100,0%

Count

% within Sexo

% within Dor Crónica

Count

% within Sexo

% within Dor Crónica

Count

% within Sexo

% within Dor Crónica

Feminino

Masculino

Sexo

Total

Sem dorcrónica

Com dorcrónica (>3 meses)

Dor Crónica

Total

Chi-Square Tests

3,915b 1 ,048

2,881 1 ,090

4,048 1 ,044

,056 ,044

3,848 1 ,050

58

Pearson Chi-Square

Continuity Correctiona

Likelihood Ratio

Fisher's Exact Test

Linear-by-LinearAssociation

N of Valid Cases

Value dfAsymp. Sig.

(2-sided)Exact Sig.(2-sided)

Exact Sig.(1-sided)

Computed only for a 2x2 tablea.

0 cells (,0%) have expected count less than 5. The minimum expected count is8,52.

b.

Results

- Participants have been divided into three age groups in order to

help us to understand the relation between age and CP.

AgeStatisti

c

Chronic Pain

[18-44]

Proportion 0,2381

CI 95% for mean

Lower Bound 0,0394

Upper Bound 0,4368

[45-64]

Proportion 0,2381

CI 95% for mean

Lower Bound 0,0394

Upper Bound 0,4368

≥65

Proportion 0,5333

CI 95% for mean

Lower Bound 0,2474

Upper Bound 0,8193

Results

- Duration of Pain – here we tried to understand the period of pain

that our participants have experienced.

12,0000 12,0000 44,2500 61,0000 120,0000 219,6000 .

48,0000 61,0000 120,0000

Duration of Pain(months)

Duration of Pain(months)

WeightedAverage(Definition 1)

Tukey's Hinges

5 10 25 50 75 90 95

Percentiles

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.

11016Mean

21026

Maximum

Intensity 

Interquartil Range

Maximum

Minimum

Median

2504Incapable joy life

4503Lonely/Isolated

3503Angry

2514Nervous/Ansious

2504Sad/Depressed

Interquartile Range

Maximum

MinimumMedian

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.

51006Life Pleasure

61007Sleep

61003

Relationship with other persons

41037Normal work

31036Ability to walk

31006Mood

31036Ample capacity

Interquartile Range

Maximum

Minimum

Median

Results

- We selected the questionnaires of the people who have pain and

tried to understand the very nature of the pain.

The pain nature

3 15,0 15,0 15,0

4 20,0 20,0 35,0

6 30,0 30,0 65,0

7 35,0 35,0 100,0

20 100,0 100,0

Constant

Variable

Periodic and regular

Periodic and irregular

Total

ValidFrequency Percent Valid Percent

CumulativePercent

Results

- Pain’s location – we present here the ranking of the locations

proposed to our participants..

Disease/problem that causes pain Frequency Proportion

Lumbar region 12 0,6

Head and neck posterior 9 0,45

Lower Limbs anterior 7 0,35

Dorsal region 6 0,3

Upper Limbs anterior 5 0,25

Lower Limbs posterior 5 0,25

Head and neck anterior 4 0,2

Thorax anterior 4 0,2

Upper Limbs posterior 4 0,2

Abdomen anterior 3 0,15

Results

- Pain’s location

12

9

7

6

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

Results

- Medically confirmed pain

Medically Confirmed Pain

6 30,0 31,6 31,6

12 60,0 63,2 94,7

1 5,0 5,3 100,0

19 95,0 100,0

1 5,0

20 100,0

Yes

No

Don't know

Total

Valid

Non responseMissing

Total

Frequency Percent Valid PercentCumulative

Percent

Results

- Professional Interference – working days lost due to pain in the last 6

months.

15 participants answered, 5 participants did not.

Descriptives

8,93 6,134

-4,22

22,09

,00

0

90

Mean

Lower Bound

Upper Bound

95% ConfidenceInterval for Mean

Median

Minimum

Maximum

Working dayslost

Statistic Std. Error

Results

- Participants were instructed to report their medication and/or

treatment.

Statistics

20 20 20 20 20 20

0 0 0 0 0 0

,85 ,20 ,15 ,00 ,05 ,05

1,00 ,00 ,00 ,00 ,00 ,00

,366 ,410 ,366 ,000 ,224 ,224

0 0 0 0 0 0

1 1 1 0 1 1

17 4 3 0 1 1

1,00 ,00 ,00 ,00 ,00 ,00

1,00 ,00 ,00 ,00 ,00 ,00

1,00 ,00 ,00 ,00 ,00 ,00

Valid

Missing

N

Mean

Median

Std. Deviation

Minimum

Maximum

Sum

25

50

75

Percentiles

Drugs PhysiotherapySwimming and/or

Hydrogym Massages Osteopathy Muscle Distress

Results

- We asked participants to report, using a 0-100 scale, their relief in

the last 6 months with treatment.

Pain relief / Treatment success

1 5,0 5,9 5,9

1 5,0 5,9 11,8

6 30,0 35,3 47,1

4 20,0 23,5 70,6

1 5,0 5,9 76,5

1 5,0 5,9 82,4

1 5,0 5,9 88,2

2 10,0 11,8 100,0

17 85,0 100,0

3 15,0

20 100,0

20

30

40

50

60

70

90

100

Total

Valid

Nonresponse

Missing

Total

Frequency Percent Valid PercentCumulative

Percent

Results

- Professional attendance – we wanted to know how many participants

are followed-up by any health professional and the most solicited ones.

Professionals Frequency

Specialist 10

GP 9

Physiotherapist 1

Osteopath 1

Psychologist 1

Nurse 1

• 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.

Conclusion / Discussion

Table: Comparative description of the characteristics of 13 studies on chronic pain

[3] Harstall C, Ospina M. Pain Clinical Updates. 2003. Available from: http://www.iasp-pain.org/terms-

p.html#Pain.

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 : http://www.wcb.ns.ca/chronicpain.pdf.

[3] Harstall C, Ospina M. How Prevalent is Chronic Pain? Pain Clinical Updates. 2003 Jun; Vol. XI,

2. Available from: http://www.iasp-pain.org/terms-p.html#Pain.

[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:

emj.bmjjournals.com.

[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.

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.

Acknowledgements

Subject’s Main Teacher: Altamiro Costa Pereira, MD, PhD

Instructor: Luis Azevedo, MD