There are currently many differences in estimates of the prevalence of chronic pain in Europe, which typically range between 10–30% of the adult population, but studies have reported prevalence as high as 50% or as low as 2% [
Although chronic pain represents a public health problem with an evident social and economical impact, there is a paucity of reliable data about its epidemiology, hindering an accurate estimation of the burden of this condition. Statistics rarely focus on chronic pain as a discrete entity. This ignores the insight of clinicians specialised in pain treatment: that chronic pain is considered a discrete entity in itself, with clear characteristics of symptoms, disability, and mental health aspects which are largely independent of the underlying disease.
Decision and policy makers in European countries make judgements on health budgets and patient segmenting and compared with cardiovascular disease, oncology, diabetes, and mental health; there appears to be limited appreciation about the importance of chronic pain. In a recent European White Paper by OpenMinds (the Opioids and Pain European Network of Minds) [
As part of a wider pan-European project [
This study was developed within the framework of a broad literature review about the epidemiology of chronic noncancer pain, across European countries including Denmark and Sweden, reviewing the scientific literature on the most recent epidemiological data on chronic pain. As far as practicable, we followed standardised processes and methods recommended by the Centre for Reviews and Dissemination (CRD) for systematic reviews [
Our extensive search strategy was developed to search for studies across European countries as part of a wider European project on the epidemiology of chronic pain, but for this paper only studies from Denmark and Sweden were utilised. In September 2009, the following databases were searched from 1995 to the end of August 2009: MEDLINE, EMBASE, The Cochrane Library, CRD Databases (DARE, HTA, and NHS EED), and GIN database. The strategy was limited to specific European countries and corresponding languages (German, French, Swedish, Spanish, Italian, Dutch, English, and Danish). Additionally we checked the reference lists of the studies deemed as relevant for the purposes of the review. Demographic data were taken from the Statistics Denmark website [
Our initial inclusion criteria were to include primary studies or systematic reviews of studies providing epidemiological data about noncancer chronic pain in Denmark and Sweden. Chronic pain was defined as painful conditions lasting at least 3 months or chronic diseases associated with pain, including musculoskeletal pain, neuropathic pain, fibromyalgia, osteoarthritis, and rheumatoid arthritis. We excluded studies with children and adolescents, conditions such as migraine and headache, angina pectoris, specific cancer pain, or pain associated with specific conditions (e.g., multiple sclerosis, Parkinson’s disease, and gastroenterological conditions). However, due to a dearth of data in identified studies (e.g., some with cancer pain patients included and some with a pain population with unknown or mixed medical diagnoses), we modified these criteria to allow for studies with mixed pain populations. We gave preference for inclusion to recent studies examining the general population, but again, where there was a dearth of data, studies of subgroups of populations were included. Studies specifically relating to cancer pain were excluded.
After defining a list of clinical questions (Supplementary Materials, Appendix 2) to address the basic issues related to chronic pain (e.g., prevalence and incidence, patient demographics, comorbidity, treatment adequacy, compliance and satisfaction with treatment, or impact on quality of life), two authors independently inspected full papers of the titles and abstracts retrieved from the searches for eligibility and determined their relevance. Papers for each included country were assessed separately. For Denmark, originally, 32 included studies were categorised to obtain a list of relevant studies per question, and from these we selected for each question the most pertinent 3 papers using the following criteria: sample size and representativeness of the general population, recency, and methodological quality. For Sweden, originally 31 included papers were categorised in the same way. Overall, 11 papers were used for our Denmark review/results and 22 papers were selected to answer research questions for Sweden, some of the papers from both countries contained data for multiple questions.
We developed quality assessment criteria by utilising 9 assessment criteria formulated in accordance with the principles of STROBE checklists on reporting guidelines for observational studies [
Despite our inclusion criteria, we did not find many studies for either country with 100% inclusion of patients with noncancer pain as sometimes this criterion was unclearly reported (Supplementary Materials, Appendix 4). Therefore, we employed the terminology: “general chronic pain” that included reporting some patients with cancer pain and unclear pain populations, that is, where the population was not guaranteed to be cancer free. In addition we aimed to include only moderate to severe chronic pain. However, this was not always clearly reported and for those studies where this was not clear we used the term “any chronic pain”; these studies included patients with mild pain.
From the 20,317 references retrieved from the searches (16,619 following deduplication), we identified 66 full text articles providing potential relevant information about chronic pain for Denmark and 163 full text articles for Sweden: these were mutually exclusive for the two countries but not mutually exclusive for the research questions (references can be supplied on request, see Flow Chart in Figure
Study inclusion flow chart.
For the Denmark review, no studies were identified that specifically reported the percentage of Danish chronic pain patients that are untreated or inadequately treated, the compliance of treated chronic pain patients in Denmark, levels of pain severity, the impact of chronic pain on isolation and helplessness, and comorbidities of people with pain. From 66 identified publications, 32 papers were deemed to have relevant data, but eleven primary studies were selected as the most relevant (i.e., able to elucidate specific answers to the review outcomes), reliable (i.e., robust in quality assessment), and up-to-date at the time of the review.
For the review of chronic pain in Sweden, from the full text articles, we identified 31 primary studies (at least three studies per question) that provided the most recent, representative, and valid data for Sweden; of which 22 papers were selected as best evidence for Sweden. Details of the included studies, study characteristics, and outcomes extracted for both countries are provided in Table
Summary of all papers included in the Denmark (
Paper and reference number, country | Number of participants, demographic data (age and gender if reported), and target population | Type of study/study quality/risk of bias and representativeness | Chronic pain condition and main study outcomes reported |
---|---|---|---|
Breivik et al. 2006 [ | Observational survey | ||
Ekholm et al. 2009 [ | Observational survey | ||
Eriksen et al. 2003 [ | Observational survey | ||
Eriksen et al. 2004 EJP [ | Observational survey | ||
Eriksen et al. 2004 Pain [ | Retrospective analysis | ||
Eriksen et al. 2006 [ | Observational survey | ||
Højsted et al. 1999 [ | Retrospective cohort study | ||
Jensen et al. 2004 [ | Observational survey | ||
Kronborg et al. 2009 [ | Observational survey | ||
Sjøgren et al. 2009 [ | Observational survey | ||
Thomsen et al. 2002 [ | Observational survey | ||
Andersson et al. 1999 J Epi Comm [ | Sampled | Observational survey | |
Andersson et al. 1999 Scand J PHC [ | Total sampled | Observational survey (and continued diagnosis registration) | |
Arvidsson et al. 2008 [ | Longitudinal study | ||
Ben-Menachem et al. 1995 [ | Observational survey | ||
Bergman et al. 2001 [ | Observational survey | ||
Bergman 2005 [ | Responders | Observational survey | |
Fricker-Pain in Europe 2003 [ | Same cohort as Breivik 2006 | Observational survey | |
Cöster et al. 2008 [ | Sampled | Observational study | |
Demmelmaier et al. 2008 [ | Observational study | ||
Ekman et al. 2005 Spine [ | Observational survey and economic study | ||
Gerdle et al. 2004 [ | Observational survey | ||
Guez et al. 2003 [ | Responders | Observational survey | |
Gummesson et al. 2003 [ | Responders | Observational survey | |
Jacobsson et al. 2007 [ | Analysed responders | Observational survey | |
Jakobsson et al. 2004 [ | Age stratified sample | Observational survey | |
Kato et al. 2006 [ | Sampled | Observational case-control study | |
Mullersdorf and Soderback 2000 Int J Rehab [ | Invited | Observational survey | |
Müllersdorf and Söderback 2000 Dis & Rehab [ | Invited | Observational survey | |
Norrbrink Budh and Lundeberg 2004 [ | Longitudinal study | ||
Raak et al. 2003 [ | Observational study | ||
Silvemark et al. 2008 [ | Observational survey | ||
Simonsson et al. 1999 [ | Sampled | Observational study |
*Study [
In the 11 included papers selected for Denmark; four studies were judged as having low risk of bias, three of which with representative results [
Of the 22 selected studies for Sweden, six [
The full review assessed outcomes of chronic pain by utilising 21 clinical questions (Supplementary Materials, Appendix 2) formulating results of which only the main outcomes are presented here.
In a European cohort which included a sample of adults from different areas of Denmark with moderate to severe pain, mean age for Denmark was 50.3 years and 57% were female. Pain sufferers were on average older in Scandinavian countries than other countries like Israel, Poland, and Italy; however, the sample did not include the elderly population in nursing homes [
In a sample of adult participants from different regions of Sweden with moderate to severe pain, mean age was 51.5 years, and 54% were female [
For Denmark, data were obtained about the prevalence of noncancer chronic pain from three of the included studies [
For Denmark, we selected three studies [
One Danish study reported that 45% of those with chronic noncancer pain rated their health as really good/good and 55% rated their health as fair/bad/very bad [
Health related disability was measured by how physically active pain sufferers were during their leisure time [
One study reported that significantly more sufferers of moderate to severe chronic noncancer pain stated their activities were restricted for more than six months compared to those without pain (adjusted OR 21.9, 95% CI 13.86, 34.6) [
Fewer (48.7%, 95% CI 44.6, 52.8) moderate to severe chronic noncancer pain sufferers reported their health as good compared to those with mild pain (80.7%, 95% CI 78.8, 82.5) or no pain (92.5%, 95% CI 91.1, 93.6). Those with moderate to severe noncancer pain scored lower on all relevant SF-36 subscales compared to those with mild pain and those without pain [
In Sweden, people with chronic pain reported reduced abilities for activities of daily living (ADL) [
Many Swedish participants with pain reported levels of depression and/or anxiety and related symptoms like insomnia [
For Denmark, we selected six studies, all with unclear representativeness but varying risks of bias, suggesting that chronic pain has an economic impact on individuals, society, and healthcare utilisation [
In Denmark, the mean number of work days lost due to moderate to severe chronic noncancer pain per respondent in the last six months was 9.4 days [
29% of Swedish participants with chronic neck pain reported being off sick due to their pain [
Costs of chronic pain in Denmark were reported in three studies. One study estimated the mean total costs of healthcare in patients applying for disability pension because of chronic noncancer pain at €4419 (Danish Krone (DKK) 33,139) per year [
We located only two studies which reported on monetary costs of chronic pain in Sweden. In people with chronic back pain total average annual direct cost per patient was (Euros) €3089 (15% of total costs), but when indirect costs were taken into account, total annual costs per patient were estimated at €20,666 [
We selected seven studies from Denmark, of which two were representative, which reported on presentation, treatment and pain control, with treatment [
In Denmark, of those with moderate to severe chronic noncancer pain, 14% had seen a pain management specialist at least once [
Of those with general chronic noncancer pain in Denmark, the proportion who had contact with a medical doctor within the last 3 months varied between 59% and 78% [
Four Denmark studies reported on the frequency of various pain treatments [
In Denmark, amongst a group of moderate to severe pain sufferers, the proportion of patients who were prescribed WHO class I, II, or III drugs was 46%, 8% and 11% respectively [
In Sweden, The most frequent WHO class drug treatments prescribed to patients with moderate to severe chronic pain in Sweden were paracetamol (26%), NSAIDs (27%) and Step II Opioids (36%), and nonprescription drugs taken were paracetamol (75%) and NSAIDS (25%) [
The most frequent nondrug pain treatments tried by those with moderate to severe general chronic pain were physical therapy (55%) acupuncture (41%) and massage (36%) [
In a sample of patients with chronic pain due to spinal cord injury (SCI) [
Only one paper from Denmark reported on duration of chronic pain [
The mean duration of pain in years in moderate to severe chronic pain was 8.3 for Denmark and 9 for Sweden [
Once again, we did not elicit any information from Demark for this outcome. We included six papers with data reporting comorbidities and underlying diseases for people in Sweden experiencing chronic pain, and once again the risk of bias and degree of representativeness assessed was varied [
In Swedish papers with data relating specifically to comorbidities, 32% of a sample with chronic upper extremity pain also experienced chronic upper extremity numbness or tingling. 20.8% of participants had a physical impairment alongside chronic pain [
The remaining studies reported on underlying disease linked to chronic pain. In chronic musculoskeletal pain (CMP), the most prevalent underlying diseases in participants were back pain, 36.7 per 1000, fibrositis-myalgia, 33.0 per 1000, and local tendinitis-bursitis, 28.6 per 1000 [
This paper was written as part of a large Europe wide project exploring the epidemiology of chronic pain in literature reviews across several discrete European countries and across Europe as a whole [
We conducted separate comprehensive epidemiological literature reviews in the broad field of chronic pain, its impact, and treatment, and we present here our methods and results for Denmark and Sweden. Overall, we assessed that although there were a number of papers elucidating data on chronic pain in both countries, our inclusion criteria of papers with noncancer chronic pain, clear representativeness to the general population, and a low risk of bias were sometimes difficult to achieve. Due to unclear reporting, we judged the validity or representativeness of the data from eight of eleven Denmark studies as unclear: only four studies were judged as low risk of bias. For Sweden, we judged the validity or representativeness of the data as having low risk of bias combined with high representativeness in just six of the 22 included papers (Supplementary Materials, Appendices 3 and 4). Only one source (with two papers reporting on both countries), reported broadly on chronic noncancer pain where less than 1% of the study population reported their pain as cancer related [
The prevalence of moderate to severe chronic pain in Denmark is estimated at 16% for moderate to severe noncancer pain [
In comparison with other chronic diseases, the overall prevalence of Type 2 diabetes mellitus in Denmark was estimated at 4% in 2007 [
The review data from both countries reported various evidence that chronic pain in both Denmark and Sweden has a clearly negative impact on quality of life, activities of daily living, physical functioning, and general wellbeing for those affected. Chronic pain in many capacities was associated with depression and anxiety, isolation and helplessness, increased sick leave, and increased uptake of benefits and pension.
Although no formal economic evaluations of chronic pain in Denmark or Sweden were found, results from several studies support the statement that chronic pain has an economic impact on society, health care resources, and the individual. Around 9 workdays per 6 months are lost due to chronic pain in Denmark, and there was an association between chronic pain and disability pensions, suggestive of economic impact of pain on society [
There is evidence that chronic pain sufferers in Denmark and Sweden are undertreated. In Denmark, between 59% and 78% of chronic pain sufferers had contact with a medical doctor in the last three months [
In Sweden, although the majority of people with chronic pain in the studies reported seeking treatment of either conventional medical care or alternative care for their chronic pain, a significant minority (35.2% in one sample [
In our reviews, we did not set out to find information regarding detail on which specific treatment modalities were deemed to be insufficient either by patients or doctors and the possible reasons for this, although this should not be ignored in future research, both primary and secondary. However it is noted that 79% of patients attending a multidisciplinary pain clinic in Denmark [
Although our literature reviews were conducted using the highest quality data available, some limitations must be acknowledged. The reviews were performed within limited time constraints and budget and were not designed to be full systematic reviews. Notwithstanding this, thorough literature reviews containing the most relevant assessed information and data, extracted and checked by two reviewers at all stages were carried out. The authors assessed many of the individual studies as having various limitations in their reporting of statistical methods and effect sizes, and in some studies, only descriptive statistics were reported. It is well documented that reporting of such research can be inadequate, and that this may make it difficult to assess generalisability of observational studies [
We also noted that many of the selected published studies for both countries were written by the same authors, often intermixed with other frequently cited authors for chronic pain; in our Denmark review, two of the authors were cited repeatedly (with other authors) in nine of our selected studies (see references); this phenomenon was less marked in our Swedish review but never-the-less there were some sets of authors writing papers on the same pain populations within similar time frames in different journals; for example, [
The authors of this paper made judgements on risk of bias and representativeness according to a quality assessment checklist (Supplementary Materials, Appendix 3) formulated in accordance with the principles of STROBE checklists on reporting guidelines for observational studies [
Chronic pain is a common and important public health problem in both Denmark and Sweden. It impacts all aspects of quality of life negatively and probably also has a negative economic impact on society, health care resources, and the individual. The results of both reviews suggest that chronic pain sufferers are undertreated and that more reliable epidemiological data are needed to fully define the burden of chronic pain in these two Scandinavian countries. In order for future treatment and management of chronic pain to be optimal in Denmark and Sweden, research should contain high-quality, relevant statistical information and be representative of relevant populations.
There are no other financial or nonfinancial competing interests that we (the authors) are aware of in relation to the publication of this study.
This study was funded by Grünenthal GmbH, Aachen, Germany. Grünenthal GmbH was given the opportunity to comment on the literature reviews, but the authors had full editorial freedom for both the reviews and the journal paper.