Chronic fatigue syndrome in military Veterans with chronic pain: An investigation into prevalence, sociodemographic characteristics, psychiatric comorbidities, and healthcare usage

Abstract: Chronic fatigue syndrome (CFS) is a debilitating illness characterized by persistent fatigue (>six months) among other symptoms. Pain symptoms (e.g., muscle and joint aches) are common and included in the diagnostic criteria for CFS but are not required for diagnosis. Despite the association between CFS and pain, few studies have examined CFS in the context of chronic pain conditions. Prior work examining CFS in the context of CP has focused on Fibromyalgia (FM) and orofacial pain (OFP)/temporomandibular pain (TMD). Both CFS and CP (including FM and OFP/TMD) are associated with higher rates of psychiatric conditions, and high rates of healthcare usage. It is unknown whether having comorbid CFS and CP increases risk for psychiatric conditions or is associated with higher rates of healthcare usage compared to other pain disorders, including FM or OFP/TMD. The current study had four objectives: 1) determine the period prevalence of comorbid CFS among VHA using military Veterans with CP; 2) compare sociodemographic characteristics of VHA users with CP+CFS to Veterans with CP without CFS; 3) compare prevalence of psychiatric outcomes and flagged history of MST among VHA users with CP+CFS to VHA users with FM or OFP/TMD; and 4) compare CP-related healthcare usage among VHA users with CP+CFS to Veterans with FM or OFP/TMD. The study was a secondary analysis of a Veteran Health Administration (VHA) dataset created in 2020 using data from 2018 and 2019 using the VHA Corporate Data Warehouse (CDW). Diagnoses were retrieved from CDW records, as well as age, sex, race, ethnicity, and rurality. Three clinic types were examined for healthcare usage (primary care, pain care, and mental health care visits associated with diagnoses indicating chronic pain), in addition to long-term opioid prescribing. Period prevalence was calculated as Total CP+CFS/Total CP. Between-group comparisons were conducted for sociodemographic variables. Multivariate logistic regressions compared groups regarding psychiatric condition and healthcare usage, except for primary care, which used a multivariate negative binomial regression. The prevalence of CP+CFS among VHA using Veterans was 0.67%. VHA users with CP+CFS were younger, and more likely female, White, and non-Hispanic, and more rural dwelling, compared to VHA users with CP without CFS. VHA users with CP+CFS were clinically more likely to have a depressive disorder compared with VHA users with FM and OFP/TMD. No clinically significant differences were observed for anxiety disorders or PTSD. No clinically significant differences were found in the usage of primary care. VHA users with FM were clinically more likely to use CP-related pain care, mental health care, and have long-term opioid prescribing, compared to VHA users with CP+CFS. VHA users with OFP/TMD were clinically less likely to use CP-related mental health care and have long-term opioid prescribing, compared to VHA users with CP+CFS. Over 15,000 Veterans who presented at the VHA in 2018 with CP also had a diagnosis of CFS. VHA users with CP+CFS did not have an increased likelihood of having a comorbid psychiatric condition (anxiety disorder, PTSD), when compared to FM or OFP/TMD. Among VHA users with CP+CFS, healthcare usage rates in specialty clinics (pain care, mental health care) were lower than VHA users with FM, but higher than VHA users with OFP/TMD. Findings suggest that specialty care is underutilized by VHA users with CP+CFS, including mental health care. Future research should investigate reasons for the lower usage rates, including examinations of referral and adoption rates.