Clinical, functional, and quality-of-life characteristics of women with comorbid fibromyalgia and irritable bowel syndrome and their associations with FIQR scores

Background Fibromyalgia (FM) and irritable bowel syndrome (IBS) frequently co-occur, sharing pathophysiological mechanisms such as central sensitization and gut-brain axis dysregulation. Given that exercise is a first-line non-pharmacological intervention for FM, detailed baseline characterization may inform future exercise-based research. This study aimed to describe the physical, functional, symptomatic, and quality-of-life profile of women with FM+IBS comorbidity in relation to FM severity, assessed continuously and, secondarily, categorically using the Revised Fibromyalgia Impact Questionnaire (FIQR). Methods This cross-sectional observational study, conducted at IRCCS “Saverio de Bellis” (Castellana Grotte, Bari, Italy), enrolled 33 women (mean age 47.7 ± 8.6 years) diagnosed with FM (2016 ACR criteria) and IBS (Rome IV criteria). Participants were stratified into three groups by FIQR score: Remission/Mild (n=7), Moderate (n=13), and High Severity (n=13). FIQR total score was analyzed as a continuous exposure using Spearman correlations with bootstrapped 95% CIs as the primary analysis; the three-group stratification was retained as a secondary, exploratory presentation. Assessments included pain (VAS), tender points, gastrointestinal symptoms (IBS-SSS), kinesiophobia (TSK), sleep quality (PSQI), physical activity (IPAQ), functional fitness tests, and quality of life (SF-36). Results Perceived pain showed the strongest association with FIQR severity (Spearman’s rho=0.57, p<0.001), with values nearly doubling in the High Severity versus Remission/Mild stratum. Physical activity level (IPAQ; exact p=0.021) differed significantly across FIQR strata, with greater inactivity in the Moderate group. Lower-limb functional strength/endurance, handgrip strength, six-minute walk distance, kinesiophobia, and SF-36 Mental Component Summary were all significantly associated with continuous FIQR (all p<0.05); the Sit-to-Stand difference across categorical strata, significant under standard ANOVA (p=0.048), lost significance under Welch’s ANOVA (p=0.148) and Kruskal-Wallis testing (p=0.072). Gastrointestinal burden remained elevated across all groups, with no clear association with FIQR severity (rho=0.29, p=0.097). Sleep quality and SF-36 scores were markedly impaired regardless of FIQR class. Conclusions In this exploratory sample, greater FM severity was primarily associated with increased pain and reduced lower-limb functional capacity, while gastrointestinal burden remained consistently elevated across the severity spectrum. These descriptive, hypothesis-generating findings may help guide the design of future, adequately powered studies addressing pain threshold, functional capacity, and gastrointestinal tolerance in exercise management of FM+IBS.