Risk of peripheral artery disease following ankylosing spondylitis, 2012-2023: a nationwide cohort study in South Korea.

OBJECTIVE: Ankylosing spondylitis (AS) is a chronic inflammatory disease linked to systemic vascular complications. Evidence regarding the association between AS and peripheral artery disease (PAD) remains limited. We investigated whether patients with AS have an increased risk of PAD using a nationwide cohort in South Korea. METHOD: Using the Korean National Health Insurance Service database (2012-2023), we conducted a nationwide matched cohort study. Patients with AS were identified by at least two diagnoses of International Classification of Diseases, 10th Revision (ICD-10) code M45 within 1 year. Incident PAD was defined as at least one outpatient visit with ICD-10 code I73.9 after the index date. After a 3 year washout period, 2846 patients with AS and 28 460 matched controls were analysed. Risk was assessed using incidence rate ratios (IRRs) and Cox proportional hazards models. RESULTS: During a mean follow-up of 4.1 years, PAD incidence was higher in patients with AS than in controls (23.6 vs 16.9 per 1000 person-years; IRR 1.40, 95% confidence interval 1.23-1.59). Females aged <60 years had the highest excess risk (IRR 1.77), followed by males aged ≥60 years (IRR 1.64). Kaplan-Meier curves showed lower PAD-free survival in patients with AS (log-rank p < 0.0001). CONCLUSION: AS was associated with an increased risk of PAD, particularly among younger females, highlighting the need for early vascular screening and tailored prevention strategies.