Prevalence of chronic pain and related risk factors in military veterans: a systematic review protocol

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.