Biologic disease-modifying antirheumatic drugs survival in late-onset axial spondyloarthritis — data from a Portuguese registry

Objectives Although axial spondyloarthritis (axSpA) typically begins before age 45, late-onset axSpA (lo-axSpA) has been widely recognized. While existing literature describes this subgroup, data on therapeutic approaches remain limited. Therefore, we aimed to evaluate the efficacy and safety of biologic DMARDs in patients with lo-axSpA.Methods We conducted a retrospective, multicentre, national cohort study using data from the Rheumatic Diseases Portuguese Register. A cut-off age of 45 years was applied to define lo-axSpA. Group differences between early- and late-onset disease activity scores were evaluated, and drug survival was assessed over 12 months. Predictors of drug discontinuation were identified using a Cox proportional hazards model.Results In total, 2256 patients were included, of whom 260 (11.5%) had lo-axSpA. Patients with late-onset disease exhibited significantly higher scores in the Ankylosing Spondylitis Disease Activity Score, Bath Ankylosing Spondylitis Disease Activity Index and Bath Ankylosing Spondylitis Functional Index at baseline, 3, 6 and 12 months. Despite these differences, both groups showed proportional reductions in disease activity scores, indicating a continuous decrease in disease activity over time. Although the late-onset group had a higher discontinuation rate during the first 12 months of treatment, lo-axSpA was not associated with an increased risk of therapy discontinuation. The primary reason for treatment discontinuation in both groups was inefficacy, with low rates of infections and other adverse events observed across the cohort.Conclusion Our study demonstrated that lo-axSpA is not associated with reduced treatment efficacy or compromised safety.