Exploring gender differences in the impact of sleep and fatigue on disease severity in rheumatoid arthritis: a moderated mediation model.

Background/aim: Rheumatoid arthritis (RA) is often accompanied by fatigue and sleep disturbances, which aggravate disease severity. Gender differences in these interrelationships remain insufficiently understood. This study aimed to examine whether fatigue mediates the association between sleep quality and disease severity in RA, and whether these pathways differ by gender. Materials and methods: A single-center study was conducted with 68 RA patients (55.9% female). Disease severity was assessed using the Routine Assessment of Patient Index Data-3, fatigue using the Bristol Rheumatology Fatigue Multidimensional Questionnaire, and sleep quality using the Pittsburgh Sleep Quality Index (PSQI). Results: Fatigue significantly mediated the relationship between poor sleep quality and disease severity (indirect effect β = 0.209, p = 0.003). While gender significantly predicted fatigue (β = 0.297, p = 0.005) and females reported higher fatigue and disease severity, gender did not significantly moderate the mediation pathway (PSQI × gender interaction β = 0.019, p = 0.856). The direct effect of sleep quality on disease severity was not significant (β = 0.047, p = 0.663), supporting a full mediation model. Menopausal status was not significantly related to symptom variation among women with RA. Conclusion: Fatigue is a key mechanism connecting poor sleep to greater disease severity in RA. The female participants reported greater symptom burden, underscoring the importance of fatigue-focused, gender-sensitive management strategies.