Prevalence of chronic non-cancer pain among military veterans: a systematic review and meta-analysis of observational studies

INTRODUCTION: Chronic non-cancer pain is common among military veterans; however, the prevalence is uncertain. This information gap complicates policy decisions and resource planning to ensure veterans have access to healthcare services that align with their needs. METHODS: Following Preferred Reporting Items for Systematic Review and Meta-Analysis Protocols, we searched MEDLINE, EMBASE, PsycINFO, CINAHL and Web of Science from inception to 9 February 2023 for observational studies reporting the prevalence of chronic non-cancer pain among military veterans. We performed random-effects meta-analysis to pool pain prevalence data across studies and used the Grading of Recommendations, Assessment, Development and Evaluation approach to evaluate the certainty of evidence. RESULTS: Forty-two studies that included 14 305 129 veterans were eligible for review, of which 28 studies (n=5 011 634) contributed to our meta-analysis. Most studies (90%; 38 of 42) enrolled US veterans, the median of the mean age among study participants was 55 years (IQR 45-62) and 85% were male. The pooled prevalence of chronic non-cancer pain was 45%; however, we found evidence of a credible subgroup effect based on representativeness of the study population. Moderate certainty evidence found the prevalence of chronic pain among studies enrolling military veterans from the general population was 30% (95% CI 23% to 37%) compared with 51% (95% CI 38% to 64%) among military veterans sampled from populations with high rates of conditions associated with chronic pain (p=0.005). CONCLUSION: We found moderate certainty evidence that 3 in every 10 military veterans from the general population live with chronic non-cancer pain. These findings underscore the importance of ensuring access to evidence-based care for chronic pain for veterans, and the need for prevention and early management to reduce transition from acute to chronic pain. Further research, employing a standardised assessment of chronic pain, is needed to disaggregate meaningful subgroups; for example, the proportion of veterans living with moderate to severe pain compared with mild pain.