OBJECTIVES: Sleep disturbance is an important contributor to poor quality of life in rheumatic disorders. This study aims to test whether clinical, autoimmune and psychological factors are associated with sleep disturbance in systemic sclerosis (SSc) compared to rheumatoid arthritis (RA) patients and controls. METHODS: 101 female subjects (SSc=33, RA=34, healthy controls=34) participated in this observational, cross-sectional, parallel group study. Sleep disturbance was assessed with the Pittsburgh Sleep Quality Index (PSQI). Other assessments included the visual analogue scale (VAS) for pain, 36-item Short-Form Health Survey (SF-36), Beck Depression Inventory (BDI) and the State-Trait Anxiety Inventory (STAI). Clinical parameters, therapeutic regimen, and serologic status were recorded. RESULTS: In SSc patients, PSQI scores were higher than in RA patients and controls. Linear regression analysis showed that in SSc patients PSQI scores was associated with BDI, disease duration, modified Rodnan skin score and VAS, while DAS28 and BDI were associated with PSQI scores in RA patients. Anti-Scl70 and ANA positive SSc patients showed higher PSQI scores compared to those ANA positive only, while no differences were observed in RA patients classified according to rheumatoid factor positivity. SSc patients treated with immunosuppressants had lower PSQI scores compared to those not on therapy, whereas only corticosteroid treatment was significantly associated with higher PSQI scores in RA patients. RA patients with disease activity higher than moderate (DAS28≥3.2) had higher PSQI scores than those with lower than moderate (DAS28<3.2). CONCLUSIONS: Longitudinal studies are needed to identify disease-specific patterns associated with sleep disturbances and the influence on sleep function induced by immunosuppressive therapy among rheumatic patients.