Objective: To investigate the clinical phenotype and treatment response in patients with rheumatoid arthritis (RA) with and without concomitant Sjögren's disease (SjD).

Methods: In this observational cohort study, patients with RA from the Swiss Clinical Quality Management in Rheumatic Diseases registry were categorised according to the presence or absence of SjD. To assess treatment effectiveness, drug retention of tumor necrosis factor-α-inhibitors (TNFi) was compared to other mode of action (OMA) biologics and Janus kinase-inhibitors (JAKi) in RA patients with and without SjD. Adjusted hazard ratios (HR) for time to drug discontinuation were compared in crude and adjusted Cox proportional regression models for potential confounders.

Results: We identified 5974 patients without and 337 patients with concomitant SjD. Patients with SjD were more likely to be female, to have a positive rheumatoid factor, higher disease activity scores, and erosive bone damage. For treatment response, a total of 6781 treatment courses were analysed. After one year, patients with concomitant SjD were less likely to reach DAS28 remission with all three treatment modalities. Patients with concomitant SjD had a higher hazard for stopping TNFi treatment (adjusted HR 1.3 [95% CI 1.07-1.6]; OMA HR 1.12 [0.91-1.37]; JAKi HR 0.97 [0.62-1.53]). When compared to TNFi, patients with concomitant SjD had a significantly lower hazard for stopping treatment with OMA (adjusted HR 0.62 [95% CI 0.46-0.84]) and JAKi (HR 0.52 [0.28-0.96]).

Conclusion: RA patients with concomitant SjD reveal a severe RA phenotype, are less responsive to treatment, and more likely to fail TNFi.