Fatigue fully mediates the relationship between poor sleep quality and disease severity in rheumatoid arthritis, and while female patients reported greater symptom burden, gender did not significantly moderate this mediation pathway.
Key Findings
Results
Fatigue significantly mediated the relationship between poor sleep quality and disease severity in RA patients.
Indirect effect β = 0.209, p = 0.003
The direct effect of sleep quality on disease severity was not significant (β = 0.047, p = 0.663), supporting a full mediation model
Disease severity was assessed using the Routine Assessment of Patient Index Data-3 (RAPID-3)
Fatigue was measured using the Bristol Rheumatology Fatigue Multidimensional Questionnaire
Sleep quality was measured using the Pittsburgh Sleep Quality Index (PSQI)
Results
Gender significantly predicted fatigue levels in RA patients, with females reporting higher fatigue and disease severity.
Gender predicted fatigue with β = 0.297, p = 0.005
55.9% of the 68-patient sample was female
Female participants reported greater overall symptom burden compared to male participants
Study was conducted at a single center with 68 RA patients total
Results
Gender did not significantly moderate the mediation pathway between sleep quality, fatigue, and disease severity.
PSQI × gender interaction β = 0.019, p = 0.856
Despite females reporting higher fatigue and disease severity, the mechanism linking sleep to disease severity through fatigue did not differ significantly by gender
The study used a moderated mediation model to test these pathways simultaneously
Results
Menopausal status was not significantly related to symptom variation among women with RA in this sample.
Menopausal status was examined as a potential factor influencing fatigue or disease severity among female participants
No significant association was found between menopausal status and symptom variation
This finding was reported as part of the subgroup analysis within the female portion of the sample
Results
The study supported a full mediation model in which sleep quality affects disease severity entirely through its effect on fatigue.
The direct path from sleep quality to disease severity was non-significant (β = 0.047, p = 0.663)
The indirect path through fatigue was significant (β = 0.209, p = 0.003)
Full mediation indicates fatigue is the key mechanism connecting poor sleep to greater disease severity in RA
Sample consisted of 68 RA patients in a single-center cross-sectional design
What This Means
This research suggests that in people with rheumatoid arthritis (RA), the connection between poor sleep and worse disease severity is not direct — instead, it works through fatigue. In other words, poor sleep leads to greater fatigue, and greater fatigue in turn leads to more severe disease symptoms. This pattern held true across the 68 patients studied, with fatigue acting as the full 'bridge' between sleep problems and disease severity. Women in the study reported higher levels of both fatigue and disease severity than men, which aligns with what is commonly observed in RA populations.
Interestingly, while being female was associated with experiencing more fatigue overall, the way that poor sleep leads to fatigue and then to worse disease severity did not differ meaningfully between men and women. This means the underlying mechanism appears to be similar across genders, even though women tend to experience a greater overall symptom burden. Additionally, menopausal status among the female participants did not appear to explain differences in symptoms.
This research suggests that addressing fatigue directly — rather than focusing solely on sleep or disease activity in isolation — may be an important strategy in managing RA. The findings highlight that fatigue-focused interventions could be relevant for all RA patients, while also recognizing that women may need additional support given their generally higher symptom burden. The study was limited by its small sample size and single-center design, which means larger studies are needed to confirm these findings.
Salmanoğlu M, Yilmaz H. (2026). Exploring gender differences in the impact of sleep and fatigue on disease severity in rheumatoid arthritis: a moderated mediation model.. Turkish journal of medical sciences. https://doi.org/10.55730/1300-0144.6113