Epidemiology of chronic non-malignant pain in Denmark

Pain 106 (2003) 221–228 www.elsevier.com/locate/pain

Epidemiology of chronic non-malignant pain in Denmark Jørgen Eriksena,*, Marianne K. Jensena, Per Sjøgrena, Ola Ekholmb, Niels K. Rasmussenb a

Multidisciplinary Pain Centre, H:S Rigshospitalet, Copenhagen, Denmark b National Institute of Public Health, Copenhagen, Denmark

Received 1 January 2003; received in revised form 2 February 2003; accepted 3 March 2003

Abstract A series of health surveys are conducted every sixth to seventh year in Denmark. In the most recent survey of 2000, a national random sample (.16 years) was drawn from the Danish Central Personal Register. Out of the original sample 12,333 (74%) were interviewed and of these 10,066 returned a completed questionnaire (SF-36). The present study includes only those who both took part in the interview and the postal questionnaire. Cancer patients were excluded. Persons suffering from chronic pain (PG) were identified through the question ‘Do you have chronic/long lasting pain lasting 6 months or more’? An overall chronic pain prevalence of 19% was found 216% for men and 21% for women. Prevalence of chronic pain increased with increasing age. Persons $ 67 years had 3.9 higher odds of suffering from chronic pain than persons in the age group 16– 24 years. Compared with married persons, divorced or separated persons had 1.5 higher odds of chronic pain. Odds for chronic pain were 1.9 higher among those with an education of less than 10 years compared with individuals with an education of 13 years or more. During a 14-day period reporters of chronic pain had an average of 0.8 days (range 0 – 10) lost due to illness compared with an average of 0.4 days (range 0– 10) for the control group (CG) (Odds Ratio (OR)) 2.0). Persons with a job which required high physical strain were more likely to report chronic pain compared with those with a sedentary job (OR 2.2). The odds of quitting one’s job because of ill health were seven times higher among people belonging to the PG. A strong association between chronic pain and poor self-rated health was also demonstrated. The PG had twice as many contacts with various health professionals compared with the CG, and the health care system was, on average, utilised 25% more (overall contacts) by the PG than by the general population. Among the persons in the PG, 33% were not satisfied with the examinations carried out in connection with their pain condition and 40% were not satisfied with the treatment offered. Nearly 130,000 adults, corresponding to 3% of the Danish population, use opioids on a regular basis. Opioids are used by 12% of the PG. q 2003 International Association for the Study of Pain. Published by Elsevier Science B.V. All rights reserved. Keywords: Pain epidemiology; Prevalence; Risk factors; Use of health care services; Use of opioids

1. Introduction Chronic non-malignant pain is a severe and frequent health care problem not only in terms of human suffering, but also in terms of the enormous economic implications for the health care system and society. Several studies on the epidemiology of pain have been carried out to estimate the prevalence of chronic pain, its demographic characteristics and consequences (Brattberg et al., 1989; Von Korff et al., 1990; Bowsher et al., 1991; Andersson et al., 1993; Bassols et al., 1999; Elliott et al., 1999; Buskila et al., 2000; Blyth et al., 2001). However, differences and inconsistencies in definitions of chronic * Corresponding author. Tel.: þ 45-3545-7382; fax: þ 45-3545-7349. E-mail address: [email protected] (J. Eriksen).

pain complicate evaluation and comparison, as is illustrated by reported prevalences ranging from 8% to 80%. Chronic pain may be more or less complex, i.e. to a varying degree involving not only biological, but also psychosocioeconomic aspects, and the studies made by Von Korff et al. (1990) and Purves et al. (1998) illustrate, that attempts in differentiating the chronic pain definitions reduce the prevalence found. Consequently, one of the epidemiological challenges is to differentiate between the occurrence of simple pain experiences and longer lasting pain conditions of a more complex nature (Raspe and Kohlmann, 1994). Apart from the study by Brinck et al. (1995), which demonstrated a prevalence of 16% of long lasting musculoskeletal diseases, no epidemiological studies directly related to chronic pain have been performed in Denmark.

0304-3959/03/$20.00 q 2003 International Association for the Study of Pain. Published by Elsevier Science B.V. All rights reserved. doi:10.1016/S0304-3959(03)00225-2

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The purpose of this study was, by using data from the 2000 Danish National Health and Morbidity Survey to (1) estimate the prevalence of chronic/long lasting pain in the Danish population; (2) estimate pain prevalence related to sociodemographic data and concurrent health characteristics; (3) evaluate associations between chronic pain and health related disability, use of medication and medical services.

2. Methods The 2000 Danish Health and Morbidity Survey is the fourth in a series of health surveys conducted in Denmark every sixth to seventh year (Rasmussen et al., 1988; Kjøller et al., 1995; Kjøller and Rasmussen, 2002). The aim of the surveys is to evaluate the general health status and morbidity in the Danish population in a given year and to monitor health status over time.

Age was categorized into four groups: 16– 24, 25– 44, 45 – 66 and $ 67 years, as suggested by Kjøller and Rasmussen (2002). Cohabitation status was assembled into five groups: married; cohabitating; divorced/separated and single; widowed and single; never married and single. The International Standard Classification of Education (ISCED), which combines school- and occupational education, was used to describe educational status (Hansen and Ku¨hl, 1994). The variable was categorized into three levels: , 10 years, 10– 12 years and $ 13 years. Physical job strain was evaluated by the following question: ‘How would you describe the physical strain of your chief occupation’: (1) mainly sedentary work which doesn’t demand any physical effort; (2) work which to a great extent is performed standing or walking but apart from that doesn’t demand any physical effort; (3) standing or walking work involving much lifting or carrying; (4) heavy or speedy work, which is strenuous.

2.1. Procedure and assessments In the 2000 survey, a national random sample of 16,684 persons over 16 years of age, was drawn from the Danish Central Personal Register and asked to participate. Data were collected via face-to-face interviews carried out by a professional interview staff from the Danish National Institute of Social Research and through selfadministered questionnaires, which included the Short Form 36 (SF-36) (Ware et al., 1993; Ware et al., 1994). Only those who took part in the interview and filled in the postal questionnaire were included in the study. Participants suffering from chronic pain were identified through the question ‘Do you have chronic/long-lasting pain lasting 6 months or more?’ Positive responders constitute the pain group (PG) and negative responders the control group (CG). Responders with a self-reported earlier or present cancer diagnosis were excluded. Table 1 shows a flow chart of the survey.

2.3. Chronic pain prevalence according to concurrent health characteristics Self-rated health status was evaluated on a 5-item scale: 1, very good health; 2, good health; 3, fair health; 4, poor health; and 5, very poor health. The presence of various symptoms that had been bothersome ‘a lot’ during the past two weeks were used to categorize the respondents as having musculoskeletal, gastrointestinal, psychological or respiratory symptoms, headache or eczema. Long-standing diseases were grouped using the WHO ICD8, which includes 14 major diagnostic groups. Calculation of Body Mass Index (BMI), based on selfreported height and weight was categorized as follow: 10– , 20; 20– , 25; 25 – , 30; and $ 30 (Kjøller and Rasmussen, 2002). Pain localization was grouped by: arms/legs/hands/ knees; back/low back; shoulder/neck; head; stomach.

2.2. Chronic pain prevalence according to sociodemographic characteristics

2.4. Health-related disability

The sociodemographic determinants of chronic pain were: sex; age; cohabitation status; educational status; and physical job strain.

The variables used were: long-lasting activity restriction (. 6 months) because of ill health (all age groups); quitting job because of ill health; and self-reported absences due to

Table 1 Flow chart for The Danish Health and Morbidity Survey of 2000 Sample (N ¼ 16,684) + Completed interview (N ¼ 12,333) + Completed postal questionnaire and interview (N ¼ 10,458) + Study population (N ¼ 10,066)

)

Non-responders (N ¼ 4,351)

)

Not completed postal questionnaire (N ¼ 1,875)

)

Lost due to cancer or irrelevant answering of questionnaire (N ¼ 392)

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illness. The variable ‘quitting job’ was constructed from two variables: ‘retiring from job for health reasons’ and ‘changing job and later retiring because of ill health’. The analysis was performed in three age groups: 16 –24, 25 –44, 45 –66 years. Self-reported absence due to illness was measured among those actively engaged in employment as the number of absent days during the 14-day period before interview.

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Table 2 Distribution of gender, age, cohabitation status, educational level and selfrated health in those who completed the interview (see also Table 1) compared with the study population Variable

Completed interview % (N ¼ 12.333)

Study population. Completed interview and postal questionnaire in relevant samples (cancer excluded) % (N ¼ 10.066)

49 (5,996) 51 (6,337)

48 (4,828) 52 (5,238)

14 (1,677) 36 (4,404) 35 (4,329) 16 (1,923)

13 37 36 14

51 (6,317) 16 (2,016) 6 (704) 7 (910) 19 (2,301)

54 (5,412) 16 (1,645) 5 (542) 6 (603) 18 (1,799)

18 (2,281) 30 (3,652) 50 (6,128)

17 (1,671) 29 (2,905) 52 (5,278)

36 (4,401) 43 (5,265) 16 (1,937) 4 (517) 2 (206)

37 (3,768) 43 (4,315) 15 (1,473) 4 (378) 1 (127)

2.5. Use of health care services To estimate utilization of different parts of the health care services, the following question was used: ‘Did you within the past 3 months consult a doctor because of personal complaints, illness or injury’? Regular use of medications was categorized according to daily intake of analgesics (non-opioids, opioids), anxiolytics, or antidepressants. Satisfaction with medical examination and treatment were assessed in the PG by the questions: ‘Are you satisfied with the medical examinations for your pain condition, which have been made till now?’ and ‘Are you satisfied with the pain treatment you have been offered till now?’ Answers were categorized as ‘Yes’ or ‘No’. 2.6. Statistical analyses Logistic regression analyses were used to assess the relation between the dependent variable (chronic pain) and the independent variables ‘Sex’; ‘Age’; ‘Cohabitation status’; ‘Education’; and ‘Physical job strain’. In logistic regression, model interpretation is possible through odds ratios, which are functions of model parameters (Hosmer and Lemeshow, 2000). Logistic regression analyses were also used to describe the consequences of chronic pain. In these analyses, ‘Chronic pain’ was used as the independent variable. All analyses were adjusted for sex and age. Mean scores were estimated for each of the SF-36 subscales. Statistical analyses were performed using SAS version 8.2.

3. Results Out of the original sample of 16,684 persons, 12,333 (74%) were interviewed and 10,458 (63%) returned the postal questionnaire. Of the latter, 392 were excluded because of cancer or an incomplete questionnaire. This left 10,066 persons for further investigation in this study (Table 1). The demographic characteristics and self-rated health for the total group and the subgroup are shown in Table 2. The investigated population of 10,066 consisted of slightly more married and fewer elderly people as compared with the sample of interviewed persons (12,333).

Sex Male Female Age 16 –24 25 –44 45 –66 67þ Cohabitation statusa Married Cohabitation Divorced/sep. Widowed Unmarried Educationa ,10 years 10 –12 years 13þ Self-rated healtha Very good Good Fair Poor Very poor

(1,328) (3,716) (3,651) (1,370)

a Does not sum to 100% or N, as some answers had to be excluded or grouped as ’unknown’.

3.1. Chronic pain prevalence according to sociodemographic characteristics The prevalence of chronic pain according to sociodemographic characteristics is shown in Table 3. The overall prevalence of chronic pain was 19 –16% for men and 21% for women. Chronic pain increased with increasing age. The prevalence of pain among persons $ 67 years of age was 29%, and their odds of suffering from chronic pain were 3.9 higher than persons in the age group 16– 24 years. Compared with married persons, those who were divorced or separated had 1.5 higher odds of chronic pain (prevalences were 27 and 19%, respectively). The prevalence of chronic pain for persons with an education of less than 10 years was 29%, compared with 14% in persons with an education of 13 years or more (odds ratio 1.9). In addition, the analysis showed that people having a job with high physical strain were more likely to report chronic pain compared with those having a sedentary job (prevalences were 21 and 12%, respectively, odds ratio 2.2).

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Table 3 Pain prevalence, odds ratios and confidence intervals in different sociodemographic groups Variable

Chronic pain prevalence (%) (cases)

All respondents 19 (1,871) Sex Male 16 (781) Female 21 (1,090) Age 16– 24 9 (126) 25– 44 13 (496) 45– 66 23 (854) 67þ 29 (395) Cohabitation status Married 19 (1,051) Co-habitation 16 (262) Divorced/sep. 27 (147) Widowed 31 (188) Unmarried 12 (211) Education ,10 years 29 (77) 10– 12 years 21 (1,027) 13þ 14 (739) Physical strain of jobb Sedentary 12 (295) Light 14 (270) Moderate 12 (224) High 21 (57) a b

Odds ratio

95% Confidence interval (CI)

1 1.4

1.3–1.6a

1 1.5 3.0 3.9

1.2–1.8a 2.4–3.6a 3.1–4.9a

compared with 2% in the CG. Quitting their job for health reasons was reported by 28% of the persons with pain compared with 5% of those without pain, and the odds of having quit a job for health reasons were seven times higher in the PG than in the CG. The odds of having at least one day of absence due to illness during the prior fortnight were twice as high in the PG as in the CG. During a 14-day period, reporters of chronic pain have an average of 0.8 (range 0– 10) days lost due to illness compared with an average of 0.4 (range 0– 10) for the CG. Table 4 Prevalence of chronic pain according to various health characteristics Variable

1 1.2 1.5 1.2 1.0 1.9 1.6 1 1 1.1 1.1 2.2

1.0–1.4 1.2–1.8a 1.0–1.5 0.8–1.1 1.7–2.2a 1.4–1.8a

0.9–1.4 0.9–1.3 1.6–3.1a

Significant values. Analysis performed among those actively engaged in employment.

3.2. Chronic pain prevalence according to concurrent health characteristics Table 4 illustrates the prevalence of pain in connection with different health characteristics. Prevalence of chronic pain increased with decreasing ratings of self-rated health. Prevalence was highest among those reporting musculoskeletal related symptoms not only for a 14-day period before being interviewed, but also as a long-standing disease. A high prevalence was found corresponding to pain localizations in the back/lower back, shoulder, neck, arms, legs, hands and knees. In addition, increasing BMI was associated with increasing prevalence of chronic pain. Compared to the CG, the PG showed consistently lower scores in all subscales of the SF-36, with the most pronounced differences (besides ‘Bodily Pain’) observed in the domains ‘Role Physical’ and ‘General Health’ (Fig. 1). 3.3. Health-related disability

Self rated health Very good Good Fair Bad Very bad 14-days symptoms Musculo/skeletal symptomsa Gastro-intestinal symptomsb Psychological symptomsc Eczemad Headache Respiratory symptomse Long standing disease Musculoskeletal Infections Digestive apparatus Traumas/injuries Endocrine diseases Urinary tract- and sex diseases Circulatory system Psychiatric diseases Nervous system Others Respiratory system Diseases in skin and subcutis Blood diseases Non malignant neoplasm’s BMI 10 – , 20 20 – , 25 25 – , 30 $30 Pain localisation Arms/legs/hands/knees Back/Low back Shoulder/neck Head Stomach a

Associations between chronic pain and activity restriction, quitting one’s job and absence due to illness during a period of 14 days, are shown in Table 5. The variable ‘chronic pain’ was clearly significant in all three analyses. Activity restriction was reported by 21% in the PG

Prevalence of chronic pain (%)

5 15 45 70 72 50 43 40 39 37 29 57 51 47 45 40 40 38 35 32 32 32 29 24 19 17 16 20 28 53 52 51 26 12

Pain or discomfort in shoulders, neck, back or loin, arms, hands, legs, knees, hips or joints. b Indigestion, diarrhoea/constipation and stomach-ache. c Depression, anxiety, nervousness, restlessness, apprehension, sleeping problems, melancholy, unhappiness, fatigue, rapid palpitation. d Eczema, rash or itching. e Colds, rhinitis or coughing, breathing difficulties.

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Fig. 1. SF-36 profiles for the PG (N ¼ 1.871) and CG (N ¼ 8.019) adjusted for sex and age. BP, bodily pain; GH, general health; MH, mental health; PF, physical functioning; RE, role emotional; RP, role physical; SF, social functioning; VT, vitality. PG, Pain Group; CG, Control Group.

3.4. Utilization of health care services

Table 7 indicates that 9% of the Danish population uses some kind of analgesic medication and 3% use opioids on a regular basis. Antidepressants were used by 2% of the total population and by 4% of the PG.

The utilization of health care services in the last three months is shown in Fig. 2. Except for use of ‘emergency room’ and ‘doctors on call’, almost twice as many persons in the PG had visited various health care professionals as compared with the CG. Table 6 shows responses to the question on satisfaction with the examinations carried out and the treatment offered in connection with the chronic pain condition. More than one-third reports not being satisfied with either the medical examinations or the treatment offered. Dissatisfaction was equally distributed among men and women, but to a higher degree observed in the younger age groups, among persons with $ 10 years of education, and among persons with poor self-rated health.

4. Discussion This is the first published study on the epidemiology of chronic pain in Denmark. The study was based on personal interviews and a large national representative survey with a high response rate. The variation in sociodemographic parameters and self-rated health between the national representative sample and the ‘Investigated sample’ are all considered negligible and analyses performed on the investigated sample were, therefore, considered unbiased

Table 5 Associations between chronic pain and activity restriction, quitting job and absence due to illness during the last 14 days Variable

Prevalence % (cases)

Mean number of absence days due to illness

Odds ratio

95% confidence interval (CI)

Activity restriction > 6 months PGa (N ¼ 1,871) CGa (N ¼ 8,194)

21% (392) 2% (190)

9.9 1

8.2–11.9

Quitting job for health reasonsb PG (N ¼ 1,475) CG (N ¼ 7,124)

28% (412) 5% (328)

7.3 1

6.2–8.6

Absence due to illnessc PG (N ¼ 772) CG (N ¼ 5,187)

17% (130) 10% (511)

2.0 1

1.6–2.4

a b c

0.8 (0–10) 0.4 (0–10)

PG, pain group; CG, control group. Analysis includes only those ,67 years. Analysis includes only those engaged in employment and ,67 years old.

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Fig. 2. Visits of PG and CG to different health care professionals during a period of three months before interview day. PG, Pain Group, CG, Control Group, GP, General Practitioner.

by the non-response. The health survey was cross-sectionally designed and, therefore, only analysis of the associations between relevant variables could be performed. However, using time-independent variables such as sex and education, this problem was minimized (Hennekens and Buring, 1987). As most of the study relied on self-reported data the analysis may be influenced by information bias. However, most of the questions were related to an actual situation, e.g. cohabitation status, age, self-rated health etc., thus minimizing the problem. Recall periods were short – 14 days in

the case of absence due to illness and various symptoms, and three months in case of utilization of health care services. Moreover, the study had limitations which are common in studying pain epidemiology: case definition and identification (Smith et al., 1996; Crombie, 1997). The definition of chronic pain accepted by the International Association for the Study of Pain (IASP) has been criticized for only including the time aspect of the pain and not involving the complexity of biopsychosocial factors, often observed in chronic pain conditions.

Table 6 Responses to the questions on satisfaction with the examinations made and treatment offered in connection with the chronic pain condition Variable

Pain group % (cases)

Satisfied with investigations performed % (cases)

Not satisfied with investigations performed % (cases)

Satisfied with pain treatment offered % (cases)

Not satisfied with pain treatment offered % (cases)

All respondents Sex Male Female Age 16– 24 25– 44 45– 66 67 þ Cohabitation status Married Cohabitation Divorced/sep. Widowed Unmarried Education ,10 years 10 – 12 years 13 þ Self-rated health Good Poor

19 (1,871)

62 (1,157)

33 (622)

50 (939)

40 (752)

42 (782) 58 (1,090)

62 (481) 62 (677)

33 (257) 33 (365)

48 (374) 52 (565)

42 (325) 39 (427)

7 27 46 21

(126) (496) (854) (395)

52 (66) 57 (284) 63 (534) 69 (274)

39 (49) 38 (188) 33 (279) 27 (106)

37 44 51 61

(47) (218) (436) (239)

49 (62) 44 (216) 41 (352) 31 (122)

56 14 8 10 11

(1,051) (262) (147) (188) (211)

61 (642) 61 (159) 63 (92) 70 (131) 59 (124)

34 (360) 35 (92) 34 (50) 27 (51) 31 (66)

50 45 52 60 46

(527) (117) (76) (113) (97)

42 (432) 44 (114) 40 (59) 31 (58) 40 (85)

26 (482) 33 (620) 40 (739)

63 (304) 60 (374) 62 (461)

31 (151) 35 (218) 33 (241)

56 (270) 47 (288) 50 (368)

34 (165) 44 (275) 41 (299)

45 (850) 55 (1,020)

64 (545) 60 (613)

30 (251) 36 (370)

55 (464) 47 (475)

34 (287) 46 (464)

J. Eriksen et al. / Pain 106 (2003) 221–228 Table 7 Self-reported regular use of medicine in the study sample, PG and CG Regular use of medicine

Study populationa % (N ¼ 10,066)

PG (%) (N ¼ 1,871)

CG (%) (N ¼ 8,019)

Analgesics Non–opioidsb Opioids Weakc Strongd Anxiolytics Antidepressants

9 9 3 2 1 1 2

30 30 12 9 3 3 4

4 4 1 1 0 1 2

a

Includes ‘Not answered’ or ‘Do not know’. Acetylsalicylic acid, paracetamol and non steroid anti-inflammatory drugs. c Codeine and tramadol. d All other opioids. b

The overall prevalence of chronic pain in Denmark was 19%, 16% for men and 21% for women. In addition to this, 33% of the patients complaining of chronic pain were not satisfied with the examinations carried out in connection with their pain condition, and 40% were dissatisfied with the treatment offered. The group of chronic pain patients used the health care system twice as much as the control group, but in spite of this, a considerable portion were still not satisfied with either the examinations or the treatment offered for their chronic pain condition. Specific patient and disease characteristics are part of the reason for this situation. However, insufficient knowledge of and inexpedient attitudes to chronic pain and chronic pain treatment in the health care system highly influence patient behaviors. Our study confirms the already known sociodemographic characteristics of chronic pain patients in developed countries, showing a majority of middle-aged women from a lower socioeconomic background and having a lower educational level (Verhaak et al., 1998). Women were found to have 1.2 –1.6 higher odds of reporting chronic pain, and persons with less than 10 years of education were found to have 1.7 –2.2 higher odds of reporting chronic pain compared with persons having an education of $ 13 years. Other studies without data on educational level have used information on self-reported job status (Bowsher et al., 1991; Andersson et al., 1993; Andersson, 1999) showing that manual work and lower social class was associated with reporting chronic pain, defined as recurrent or persistent pain lasting . 3 months. Heavy work or obesity has been argued as a cause of low back pain as a result of increased mechanical load on the spine (Lake et al., 2000; Liira et al., 1996). Similar conclusions may be deduced from our study in which we found that persons with a high BMI or with a job requiring high physical strain were more likely to report chronic pain. Von Korff et al. (1988); Blyth et al. (2001) have demonstrated a strong association between the reporting

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of chronic pain and poor self-rated health. Poor self-rated health has extensive consequences and is associated with a high morbidity resulting in reduced working capacity (Lissau et al., 2001). Persons with chronic pain in this study had twice the odds for absence due to illness than persons without pain complaints. The odds of ever having quit a job for health-related reasons in were seven times higher among the pain population compared with the controls. Almost identical data were found by Blyth et al. (2001) when investigating chronic pain conditions lasting more than 6 months. Chronic pain patients are extensive users of health care services in the primary as well as the secondary health care sector (Von Korff et al., 1991; Becker et al., 1997; Buskila et al., 2000). Chronic pain is obviously a severe burden not only to the patient, but also to the health care system. In a study dealing with severely chronified and complex chronic pain patients it was demonstrated that this patient category had 4– 5 times as many in-hospital days per year (11.3 days/ year) as the general population (Becker et al., 1997). In this study, utilization of health care system was, on average, 25% higher for the PG than the CG (overall contacts) and the use of in-hospital days was more than twice as high. National and international statistics report opioid use in defined daily doses (DDD). Using this estimation, Denmark has the highest legal use of opioids in the world (Clausen et al., 1995). The present study reveals the actual number of persons treated with opioids, showing that 3% of the Danish population, corresponding to nearly 130,000 adults, uses opioids on a regular basis. In the PG, 12% used opioids regularly. Addiction is seldom a problem in the treatment of cancer pain patients. However, chronic non-malignant pain patients are a non-homogenous group including not only patients with physical pain problems, but also patients with severe psychosocial problems. Even if opioids are indicated in some chronic non-malignant pain conditions, there is a risk that the opioid administration, which aimed initially to try and solve the pain problem, may become a further complication and part of the chronic pain problem (Savage, 1996). Future consequences of the Danish liberal use of opioids are unknown. In conclusion, analysis of a nationally representative sample of the Danish population found an overall prevalence of chronic pain of 19%, 16% for men and 21% for women. Among persons complaining of chronic pain (. 6 months) 33% were not satisfied with the examinations carried out in connection with their pain condition and 40% were not satisfied with the treatment offered. Well known sociodemographic characteristics of chronic pain patients in the developed countries were confirmed, showing a majority of middle-aged women with a lower socioeconomic background and a lower educational level. A strong association between the reporting of chronic pain and poor self-rated health was demonstrated and the risk of absence due to illness or ‘quitting one’s job’ for health reasons was significantly increased. Chronic pain is

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obviously a severe burden not only to the patient but also to the health care system, which was utilized, on average, 25% more (overall contacts) by the pain population than by the general population.

Acknowledgements The study was supported by The Danish Foundation of Medical Technology Assessment.

References Andersson GBJ. Epidemiologicial features of chronic low back pain. Lancet 1999;354:581–5. Andersson HI, Ejlertsson G, Leden I, Rosenberg C. Chronic Pain in a Geographical Defined General Population: Studies of Differences in Age. Gender, Social Class and Pain Localization. Clin J Pain 1993;9: 174– 82. Bassols A, Bosch F, Campillo M, Can˜ellas M, Ban˜os J-E. An epidemiological comparison of pain complaints in the general population of Catalonia (Spain). Pain 1999;83:9– 16. Becker N, Thomsen AB, Olsen AK, Sjøgren P, Bech P, Eriksen J. Pain epidemiology and health related quality of life in chronic nonmalignant pain patients referred to a Danish multidisciplinary pain center. Pain 1997;73:393 –400. Blyth FM, March LM, Brnabic AJM, Jorm LR, Williamson M, Cousins MJ. Chronic pain in Australia: a prevalence study. Pain 2001;89:127–34. Bowsher D, Rigge M, Sopp L. Prevalence of chronic pain in the British population: a telephone survey of 1037 households. The Pain Clinic 1991;4:223–30. Brattberg G, Thorslund M, Wikman A. The prevalence of pain in a general population. The results of a postal survey in a county of Sweden. Pain 1989;37:215–22. Brinck B, Rasmussen NK, Kjøller M, Thomsen LK. Muskuloskeletale sygdomme i Danmark. Copenhagen: National Institute of Public Health; 1995. Buskila D, Abramov G, Biton A, Neumann L. The Prevalence of Pain Complaints in a General Population in Israel and Its Implications for Utilization of Health Services. J Rheumatol 2000;27:1521–5. Clausen TG, Eriksen J, Borgbjerg FM. Legal opioid consumption in Denmark 1981 - 1993. Eur J Clin Pharmacol 1995;48:321– 5. Crombie IK. Epidemiology of persistent pain. In: Jensen TS, Turner JA, Wiesenfeld-Hallin Z, editors. Progress in pain research and management. Proc. 8th World Congress on Pain, Vol. 8. Seattle: IASP Press; 1997. p. 53–61. Elliott AM, Smith BH, Penny KI, Smith WC, Chambers WA. The epidemiology of chronic pain in the community. Lancet 1999;354: 1248–52.

Hansen A, Ku¨hl K, (Danish educational nomenclature) Dansk uddannelses nomenklatur. Copenhagen: Danish Statistics and Ministry of Education; 1994. Hennekens CH, Buring JE. Epidemiology in medicine. Boston/Toronto: Little, Brown and Company; 1987. Hosmer DW, Lemeshow S. Applied logistic regression. New York: Wiley; 2000. Kjøller M, Rasmussen NK. The Danish health and morbidity survey 2000 and trends since 1987. Copenhagen: National Institute of Public Health; 2002. Kjøller M, Rasmussen NK, Keiding L, Petersen HC, Nielsen GA. English summary available at: www.niph.dk. The Danish Health and Morbidity Survey, 1994. Copenhagen: The Danish Institute of Clinical Epidemiology; 1995; English summary available at: www.niph.dk. Lake JK, Power C, Cole TJ. Back pain and obesity in the 1958 British birth cohort: cause or effect? J Clin epidemiol 2000;53:245–50. Liira JP, Shannon HS, Chambers LW, Haines TA. Long-Term Back Problems and Physical Work Exposures in the 1990 Ontario Health Survey. Am J Public Health 1996;86:382–7. Lissau I, Rasmussen NK, Hesse NM, Hesse U. Social differences in illness and health-related exclusion from the labour market in Denmark from 1987 to 1994. Scand J Public Health 2001;29(55):19–30. Purves AL, Penny KI, Munro C, Smith BH, Grimshaw J, Wilson B, Smith WC, Chambers WA. Defining chronic pain for epidemiological research - assessing of subjective definition. The Pain Clinic 1998;10: 139 –47. Rasmussen NK, Groth MV, Bredkjær SR, Madsen M, Kamper-Jørgensen F. Sundhed og sygelighed i Danmark 1987 – en rapport fra DIKE’s undersøgelse. Copenhagen: The Danish Institute of Clinical Epidemiology; 1988. Raspe H, Kohlmann T. Disorders characterised by pain: a methodological review of population surveys. J Epidemiol Community Health 1994;48: 531 –7. Savage SR. Long-term opioid therapy: Assessment of consequences and risks. J Pain Symptom Manage 1996;11:274–86. Smith BH, Chambers WA, Smith WC. Chronic pain: Time for epidemiology. J R Soc Med 1996;89:181 –3. Ware JE, Snow KK, Kosinski M, Gandek B. SF-36 Health Survey manual and interpretation guide. The Health Institute: Boston, MA: New England Medical Center; 1993. IQOLA Project Group, Ware JE, Gandek B. The SF-36 Health Survey: Development and use in mental health research and the IQOLA project. Int J Ment Health 1994;23:49–73. Verhaak PFM, Kerssens JJ, Dekker J, Sorbi MJ, Bensing JM. Prevalence of chronic benign pain disorder among adults: a review of the literature. Pain 1998;77:231–9. Von Korff M, Dworkin SF, LeResche L, Kruger A. An epidemiologic comparison of pain complaints. Pain 1988;32:173–83. Von Korff M, Dworkin SF, LeResche L. Graded chronic pain status: an epidemiologic evaluation. Pain 1990;40:279– 91. Von Korff M, Wagner EH, Dworkin SF, Saunders KW. Chronic pain and use of ambulatory health care. Psychosom Med 1991;53:61–79.