Authors
- VanDenKerkhof, Elizabeth G RN, DrPH
- Carley, Meg E BSc
- Hopman, Wilma M MA
- Ross-White, Amanda MLIS, AHIP
- Harrison, Margaret B RN, PhD
Abstract
Review question/objective: The objective of this systematic review is to examine the evidence on the prevalence of, and risk factors associated with, chronic pain in military veterans.
The specific review question is: What is the prevalence of chronic pain and what are the related risk factors in military veterans?
Background: Chronic Pain is of major concern to global health and one of the top reasons for a patient to seek physician care. It has been estimated that each year 10% of adults will be diagnosed with chronic pain.1 Chronic pain is defined by the International Association for the Study of Pain (IASP) as "pain without apparent biological value that has persisted beyond the normal tissue healing time (usually taken to be three months)".2 In Canada, chronic pain is highly prevalent with estimates ranging from 18%-35%,3-6 while prevalence worldwide is estimated to be approximately 30%.7 Chronic pain carries an enormous economic burden. The estimated total cost of pain to society including both health care costs and lost productivity in 2010 dollars ranges from $560-$635 billion/year in the US8 and ~$60 billion/year in Canada.9 In Canada, the wait time to access pain treatment facilities may often exceed six to eight months,10 while concurrently these patients are suffering severe pain and half with severe depression.11
Chronic pain is difficult to manage once incurred and is associated with high levels of disability and poor health. There is a propensity in the literature to report intervention studies of various drug treatment strategies for chronic pain management. However, even maximally tolerated doses of the best agents reduce pain intensity by only 26 to 38%.12 Studies on drug treatment interventions often fail to address the characteristics that contribute to the development chronic pain. Certain vulnerable populations, e.g. low socioeconomic status, racial and ethnic minorities, veterans, women and the elderly, have been identified as being at higher risk of developing chronic pain.13-15 Very little is known about interventions or measures that reduce the risk of developing chronic pain in the general population.
In the United States and internationally, chronic pain in veterans has received substantial attention, in particular veterans of recent wars overseas (Persian Gulf War and Operations Enduring Freedom and Iraqi Freedom (OEF/OIF), while in Canada, there is a paucity of literature on chronic pain, and related risk factors in veterans.13,16 A veteran is defined as an ex-member of the armed forces.17
The purpose of this systematic review is to examine the available evidence related to the burden and related risk factors of chronic pain in military veterans. Military veterans were chosen as the focus of this review due to their unique background and exposures and they have been identified as being at high risk for developing chronic pain. A more precise estimate of prevalence and potential risk factors for chronic pain in veterans has immediate implications in that vulnerable groups could be identified and measures could be taken to reduce their risk of exposure to activities that could lead to chronic pain. It also has research implications, whereby interventions could be tested in high-risk subgroups of veterans.
A search of the JBI Library of Systematic Reviews, Cochrane Library, MEDLINE and CINAHL found no existing systematic review on the epidemiology of chronic pain in the general veterans population. There have been several reviews that have examined chronic pain among veterans but were primarily limited to those with traumatic brain injury, only included veterans of the Persian Gulf War or were an investigation of co-morbid Post Traumatic Stress Disorder (PTSD) and chronic pain. Very little is known about contributing factors of developing chronic pain and preventative measures in the general military veteran population.
Article Content
Inclusion criteria
Types of participants
In this review we will consider studies that include military veterans conducted worldwide. Studies that include participants on active duty will be excluded unless the data is separated and analyzed by veterans vs. active duty service personnel.
Focus of the review
In this review we will consider studies that evaluate the prevalence and/or contributing factors associated with the occurrence of chronic pain in the general military veteran population. Studies which focus solely on a specific subset of veterans (e.g. amputees only) or conducted at specialty care centres (e.g. pain management clinic) will be excluded because these samples will inflate the overall prevalence of chronic pain. If numbers permit, subgroup analysis may be conducted on specific subgroups within the population level studies.
Type of outcomes
This review will consider studies that measure the outcome of chronic pain
Types of independent variables
This review will also consider studies that identify factors that increase the risk of chronic pain.
Types of studies
This review will include both analytical and descriptive epidemiological study designs including prospective and retrospective cohort studies, and cross sectional studies.
Search strategy
The search strategy aims to find both published and unpublished studies. A three-step search strategy will be utilized in this review. An initial limited search of MEDLINE and CINAHL will be undertaken followed by analysis of the text words contained in the title and abstract, and of the index terms used to describe article. A second search using all identified keywords and index terms will then be undertaken across all included databases. Thirdly, the reference list of all identified reports and articles will be searched for additional studies.
English language studies published between 1996 and 2013 will be considered for inclusion in this review. A series of exploratory searches in five databases (MEDLINE, Embase, PsychINFO, CINAHL, Web of Science) on studies published prior to 1996, did not yield any citations relevant to this review.
In consultation with a Health Sciences Librarian, the databases to be searched include: MEDLINE, CINAHL, Embase, PsycINFO, and Web of Science.
The search for unpublished studies will include: Dissertations and theses, MedNar, Centers for Disease Control and Prevention (CDC).
Initial keywords to be used will be: Chronic Pain, Pain, Pain Measurement, Veterans, Military Personnel, Civil Defense.
All identified studies will be assessed for relevance to the review based on information provided in the title, abstract, and subject terms. Full papers will be retrieved for studies that satisfy the inclusion criteria, or if the there is uncertainty regarding relevance. Studies identified from reference list searches of included studies will be assessed for relevance based on the title.
Assessment of methodological quality
Papers selected for retrieval will be assessed by two independent reviewers for methodological validity prior to inclusion in the review using standardized critical appraisal instruments from the Joanna Briggs Institute Meta Analysis of Statistics Assessment and Review Instrument (JBI-MAStARI) (Appendix I). Any disagreements that arise between the reviewers will be resolved through discussion, or with a third reviewer.
Data collection
Data will be extracted from papers included in the review using the standardized data extraction tool from JBI-MAStARI (Appendix II) by two reviewers, independently. The data extracted will include specific details about the interventions, populations, study methods and outcomes of significance to the review question and specific objectives. If information is missing or unclear, the corresponding author for the study in question will be contacted.
Data synthesis
Quantitative data will be combined into statistical meta-analysis, if the heterogeneity is suitable. Data will be pooled using a random effects model and heterogeneity will be assessed statistically using the standard Chi-square. All results will be subject to double data entry. Prevalence data will be measured as a proportion. Associations with developing chronic pain will be expressed as odds ratio or relative risk. Where statistical pooling is not possible the findings will be presented in narrative form including tables and figures to aid in data presentation where appropriate. Given the inclusion criteria to only consider studies which have samples that are representative of the military veteran population as a whole, subgroup analyses to explain variations in treatment effect are not applicable.
Conflicts of interest
The authors have no conflicts of interest to declare.
References
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Appendix I: Appraisal instruments
MAStARI appraisal instrument[Context Link]
Appendix II: Data extraction instruments
MAStARI data extraction instrument[Context Link]
Keywords: Chronic Pain; Pain; Pain Measurement; Veterans; Military Personnel; Civil Defense