The socioeconomic status of patients with ankylosing spondylitis and its association with the burden of the disease and permanent disability: a cross-sectional cluster analysis

Background: Few studies have been conducted to investigate the socioeconomic profiles of patients with ankylosing spondylitis (AS) and their associations with disease severity and disability.Objectives: The objectives of this study were to identify clusters of patients with AS according to their socioeconomic characteristics and to evaluate the associations between these clusters and the severity of the disease and permanent disability.Design: This was a cross-sectional and multicentre study.Methods: Patients with AS from the REGISPONSER study were included in this analysis. A cluster analysis was conducted using information on sociodemographic (age, sex, race, marital status, education) and socioeconomic (employment, profession, housing conditions and social level) characteristics. Disease burden and permanent disability were compared between the different clusters using logistic regression adjusted for disease duration and disease activity.Results: A total of 866 patients with AS were included. Two clusters were identified according to socioeconomic characteristics: Cluster 1 (n= 476), with a predominantly low socioeconomic profile, and Cluster 2 (n= 390), with a predominantly high socioeconomic profile. After adjusting for disease duration, patients in Cluster 1 had a longer diagnosis delay, greater body mass index and greater structural damage than those in Cluster 2. Access to biologic disease-modifying anti-rheumatic drugs (bDMARDs) was similar for both groups. However, patients in Cluster 1 had a greater prevalence of permanent disability than those in Cluster 2 after adjusting for disease duration and disease activity (30.8% vs 13.2%, odds ratio 2.58 (95% confidence interval 1.76–3.83)).Conclusion: This study suggests that the socioeconomic status of patients with AS may have implications for disease severity and permanent disability, despite the similar use of bDMARDs.