Characteristics of Late-Onset Spondyloarthritis: Data from the Moroccan Registry of Biological Therapies in Rheumatic Diseases.

Introduction The Assessment of SpondyloArthritis International Society (ASAS) criteria for axial and peripheral spondyloarthritis (SpA) allow for the classification of patients with an age of onset of disease of less than 45 years. However, SpA can start after this age. This study aimed to assess the characteristics of late-onset SpA (SpA>45 years) in the Moroccan registry of biological therapies in rheumatic diseases (RBSMR). Methods A cross-sectional study was conducted using the baseline data of the RBSMR. The protocol for the original RBSMR study was reviewed and approved by the Ethics Committee for Biomedical Research Mohammed V University - Rabat, Faculty of Medicine and Pharmacy of Rabat (approval number for the study was 958/09/19, and the date of approval was September 11, 2019), and all patients had given their written consent. Patients who met the 2009 ASAS criteria for SpA were included. They were divided into two groups: early-onset SpA (≤ 45 years) and late-onset SpA (>45 years). Clinical, biological, radiological, and therapy data of the two groups were compared. Statistical analysis was performed using SPSS v25 software (IBM Corp. Armonk, NY). Parameters with a p-value ≤0.05 were considered significant. Results Our population consisted of 194 patients. Thirty-one patients (16%) had late-onset SpA. Comparison between patients with early-onset (≤45 years) and late-onset SpA (>45 years) revealed that late-onset SpA had a higher tender joint count (p=0.01), a higher swollen joint count (p=0.02), depression (p=0.00), fibromyalgia (p=0.001), hypercholesterolemia (p=0.01), and a lower frequency of coxitis (p=0.008). Logistic regression analysis confirmed that late-onset SpA was associated with a higher tender joint count (OR=0.93, CI 95%: 0.88-0.98), a higher swollen joint count (OR=0.92, CI 95%: 0.85-0.99), depression ( OR=0.19, CI 95%:0.04-0.38), fibromyalgia (OR=1.75, CI 95%: 1.74-17.85), and a lower frequency of coxitis ( OR=0.29, CI 95%: 0.11-0.75). Conclusion As life expectancy increases, late-onset SpA will become increasingly common. It is therefore imperative to determine its characteristics. In the RBSMR study, late-onset SpA was associated with a high number of tender and swollen joints, depression, fibromyalgia, and a lower frequency of coxitis.