Risk of anxiety disorder following ankylosing spondylitis, 2012-2023: a nationwide cohort study in South Korea.

Introduction: Ankylosing spondylitis (AS) is a chronic inflammatory rheumatic disease associated with impaired quality of life and psychiatric comorbidities. Although depression has been widely studied in AS, the risk of anxiety disorders remains unclear. This study examined the long-term risk of anxiety disorders in patients with AS using a nationwide Korean cohort. Methods: Using the Korean National Health Insurance Service database (2012-2023), we identified patients newly diagnosed with ankylosing spondylitis (ICD-10 code M45) after applying a 3-year washout period to minimize inclusion of pre-existing cases. Patients with a prior history of anxiety disorders were excluded. Each case was propensity score-matched at a 1:10 ratio with controls by age, sex, and index year. The primary outcome was incident anxiety disorder (ICD-10 codes F40-F41). Adjusted hazard ratios (aHRs) and 95% confidence intervals (CIs) were estimated using Cox proportional hazards models. Results: We analyzed 2,762 patients with AS and 27,620 controls over a mean follow-up of 4.02 years. The incidence rate of anxiety disorder was 27.38 per 1,000 person-years in AS and 18.91 in controls (IRR, 1.45; 95% CI, 1.28-1.63). AS was associated with a 40% higher risk of anxiety disorder (aHR, 1.40; 95% CI, 1.14-1.73), with the strongest association in females <60 years (aHR, 1.87; 95% CI, 1.52-2.30). Conclusions: AS increases the risk of anxiety disorders, particularly in younger females. Therefore, early psychiatric screening should be considered during AS management.