Epidemiology of Chronic Pain in Denmark and Sweden

Introduction. Estimates on the epidemiology of chronic pain vary widely throughout Europe. It is unclear whether this variation reflects true differences between populations or methodological factors. Information on the epidemiology of chronic pain can support decision makers in allocating adequate health care resources. Methods. In order to obtain epidemiological data on chronic pain in Denmark and Sweden, we conducted a literature review of epidemiological data primarily on chronic noncancer pain, prioritising studies of highest quality, recency, and validity by conducting a systematic search for relevant studies. Following quality assessment, data were summarised and assigned to the research questions. Results. The prevalence of moderate to severe noncancer pain was estimated at 16% in Denmark and 18% in Sweden. Chronic pain impacts negatively on perceived health status, quality of life and is associated with increased cost. Despite using pain medications, a large proportion of chronic pain sufferers have inadequate pain control. There was a lack of high-quality and low-bias studies with clear inclusion criteria. Conclusions. In both Denmark and Sweden, chronic pain is a common health problem which is potentially undertreated and warrants attention of health care workers, policy makers and researchers. Future research should utilise clear reporting guidelines to assist decision and policy makers, in this important area.

If they did not report all of the above -the description was inadequate.
Select Unclear if authors reported design and setting information but it was presented unclearly or incompletely (e.g. the number of general practices was not reported or only the recruitment start date was reported, etc) 2. Was there an adequate description of eligibility criteria? Y, N or unclear As a minimum, authors should have described inclusion/exclusion criteria (e.g. chronic pain patients had to have pain continuously for at least 3 months, cancer pain was excluded, etc) and they should have taken some step to confirm the diagnosis or, in the case of interviewed health professionals, the authors should have provided confirmation that the doctors' patients were correctly diagnosed (e.g. the authors conducted a physical examination or cross-checked with a patient register to confirm diagnosis).
If they did not give any inclusion/exclusion criteria and they did not confirm the diagnosis (e.g. authors did not report that arthritic pain patients were examined to confirm pain was due to arthritis) then the description was inadequate.
Select Unclear if authors reported eligibility criteria but it was presented unclearly or they did not confirm the diagnosis (e.g. chronic pain was an inclusion criterion but chronic pain was not defined or they did not confirm the included participants had chronic pain).

Is the study population representative of the target population? Y, N, Unclear
Note -for this question, the target population is the population studied in the study, not the population that we are studying for this project (e.g. if study examines the prevalence of chronic back pain in nurses, this question asks whether the study population was likely representative of a nursing population) The authors should have described how the sample size was arrived at and how the patients were selected (e.g. consecutive vs. non-consecutive patients entering pain clinic, random postal or telephone survey) and the demographics of the sample should have been described as comparable to the target population. For surveys, an attempt should have been made to compare non-responders to responders.
If the authors reported the above and there is good reason to doubt that the population was representative (e.g. significantly more women than men responded to a postal survey when compared to the non-responder group and the results were not adjusted for this) then the population was not representative.
Select Unclear if the authors did not report or discuss comparability with their target population (e.g. a telephone survey of the general population but authors did not state whether demographics of sample were comparable to the general population)

Is there an adequate description of outcomes? Y, N, Unclear
Note -as there are as many outcomes as there are questions, this question must necessarily reflect all the outcomes measured in the study If authors generally described how they measure the outcome and clear definitions were given for key terms (e.g. one year prevalence, incidence per 100 000, what they meant by adequate treatment, untreated, etc.) then the outcomes were adequately described.
If authors failed to describe how they measured their outcomes and if they failed to describe or qualify key terms (e.g. they measured prevalence but did not qualify it as life time, year long, etc) then the outcomes were not adequately described.
Select Unclear if the descriptions or definitions were unclear (e.g. authors described patients as inadequately treated but did not provide the standard of treatment for comparison -like a clinical guideline)

Is there an adequate description of statistical methods? Y, N, Unclear
If the authors described their statistical methods and described potential confounders or effect modifiers and how they were dealt with, then the statistical methods were adequately described If the authors failed to describe all of the above then the description of statistical methods was inadequate Select Unclear if the authors described their methods but it was difficult to ascertain exactly how or why they used their methods.

Is there an adequate description of the study participants? Y, N, Unclear
If the authors provided more than just age and gender (e.g. pain duration, occupations, pain type, etc.) then the participants were adequately described If authors only provided age and gender then the description was inadequate Select Unclear if the population descriptions were unclear (e.g. numbers in texts and figures didn't match or add up).

Was there an adequate description of losses to follow-up (plus -were losses to follow-up too high)? Y, N, Unclear, Not Applicable
If authors clearly described the losses to follow-up or if the loss was <10% by 12 months and <25% for periods longer than 12 months, then this was adequate If authors did not describe the losses to follow-up or if the loss is >10% by 12 months and >25% for periods longer than 12 months, then this was inadequate Select Unclear if authors described losses to follow-up but it was difficult to follow, incomplete or the numbers in the text do not match figures.
Select Not Applicable if there was no follow-up (i.e. not a longitudinal study).  1-Adequate description of study design and setting, 2 -Adequate description of eligibility criteria, 3 -Study population is representative of target population, 4 -Adequate description of outcomes, 5 -Adequate description of statistical methods, 6 -Adequate description of study participants, 7 -Adequate description of losses to follow-up, 8 -Results reported as unadjusted or confounder-adjusted N -no, NA -not applicable, UC -unclear, Y -yes