Sociodemographic Factors, but Not Rurality, Explain Limited Variance in Fibromyalgia Severity: A Secondary Analysis of Two Randomized Clinical Trials

Abstract Objective Fibromyalgia is characterized by a broad spectrum of symptoms such as pain, fatigue, and psychosocial impairments that collectively contribute to disease severity. This study aims to investigate the influence of living in rural versus urban settings on fibromyalgia severity. Methods This is a secondary analysis of baseline data from 685 participants combined from two clinical trials. Survey data collected at baseline included sociodemographic characteristics (sex, age, rurality, race, ethnicity, income, education, employment status), pain and pain interference, fatigue, pain catastrophizing, and the Fibromyalgia Impact Questionnaire-Revised (FIQR). Results Study participants were 50.6±14.2 years, 96% female, and 44% resided in rural areas. FIQR was significantly associated with age (F = 5.511, p < 0.001), race (t=-3.628, p < 0.001), marital status (t = 3.410, p < 0.001), education status (F = 5.887, p = 0.003), employment status (t=-3.153, p = 0.002), and income (F = 13.147, p < 0.001) but not rurality (t=-0.350, p = 0.726). Cluster analysis based on rurality and sociodemographic variables resulted in two groups that differed by age, race, employment status, and income; FIQR was higher among those who were older, non-White, unemployed and with lower income. Using linear regression, sociodemographic variables contributed less than 10% of the variance in disease severity as measured by FIQR (R2=0.09) while rurality did not contribute. Additionally, sociodemographic variables contributed minimally to pain severity (9%) and interference (8%), widespread pain (4%), fatigue (6%), and pain catastrophizing (12%). Conclusions Rurality and sociodemographic characteristics had limited influence on pain, fatigue, and pain catastrophizing, suggesting that fibromyalgia disease severity is minimally influenced by sociodemographic variables and not by rurality.