Prevalence of Chronic Pain among Military Veterans and Research Priorities among Military Veterans Living with Chronic Pain

INTRODUCTION: There is uncertainty in the prevalence of chronic non-cancer pain (CNCP) in military veterans. A systematic review and meta-analysis was conducted to elucidate this issue, and examine potential effect modifiers of CNCP prevalence. Additionally, chronic pain is a pervasive and debilitating condition that disproportionately affects military veterans. We recently completed a qualitative study of Canadian veterans living with chronic pain to identify their research priorities; however, the generalizability of our findings was uncertain. METHODS: MEDLINE, EMBASE, PsycINFO, CINAHL, Web of Science were searched from 2013 to January 21, 2021, for observational studies reporting “chronic pain” or pain ≥ 3 months in military veterans. The random-effects meta-analysis was used for pooling data, the Grading of Recommendations, Assessment, Development and Evaluations approach was used for rating quality of evidence, and the Instrument to Assess the Credibility of Effect Modification Analyses was used to rate credibility of the subgroup analyses. Furthermore, from January to March 2021, we emailed a 45-item cross-sectional survey to a list of Canadian veterans that asked about the relative importance of 20 research priorities regarding chronic pain. We explored for statistical significance between male and female responses for any item in which the proportion of endorsement showed a ≥10% difference. RESULTS: 41 observational studies with 5,550,375 military veterans were included. The overall pooled CNCP prevalence is 34% (95% confidence interval (CI) 25% to 45%). However, significant subgroup effect was found for type of prevalence measure (generic or specific) among military veterans (test of interaction p=0.007, moderate subgroup credibility): the pooled generic CNCP prevalence of 43%, 95% CI 29% to 57% (Low-certainty evidence) vs. the pooled specific type of CNCP prevalence of 14%, 95% CI 6.7% to 23% (Moderate-certainty evidence). A multivariable meta-regression model adjusted for proportion lost to follow-up found the type of prevalence measure to be the only significant predictor of CNCP prevalence (p < 0.0001). 313 of 699 Canadian military veterans living with chronic pain completed ≥50% of the survey (45% response rate). Respondents were predominantly male (77%) with a median age of 52 (interquartile range [IQR] 44-58). All 20 research priorities listed in the survey were endorsed as very important by ≥52% of respondents, and three received endorsement by ≥85%: (I) optimizing chronic pain management after release from the military; and (II) identifying and (III) treating mental illness among veterans living with chronic pain. Women were more likely than men to endorse research on post-surgical care for chronic pain prevention or research on holistic care for chronic pain. Men were more likely than women to endorse research on physical activity or exercise for chronic pain. Individuals with higher gross income (≥$80,000) were less likely to endorse research into physiotherapy for chronic pain, or chiropractic for chronic pain compared to those with lower gross income. Individuals with greater age are less likely to endorse research on medical cannabis for chronic pain. CONCLUSIONS: The overall prevalence of CNCP is 34% among military veterans. For generic CNCP, the prevalence is 43%; for a given subtype of CNCP, the prevalence is 11%. Methodologically robust studies are required to more precisely determine CNCP prevalence. The most salient research priorities among our respondents were optimizing chronic pain management during service and after discharge from the military, including co-morbid mental illness. Differences in gender, gross income, and age are implicated in the endorsement of therapy-related priorities, which include surgery, physical activity or exercise, chiropractic, and medical cannabis. Our findings provide insight into the research priorities of Canadian military veterans living with chronic pain. These findings should be considered by granting agencies when formulating calls for proposals, and by researchers who wish to undertake research that will address the needs of military veterans living with chronic pain.

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