OBJECTIVE: To identify factors associated with elevated arterial stiffness in a 5-year follow-up of patients with ankylosing spondylitis (AS). METHODS: C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), Bath AS disease activity index (BASDAI) and AS disease activity score (ASDAS) were recorded in 2003, and arterial stiffness (Augmentation Index (AIx) and pulse wave velocity (PWV)) in 2008/2009. Patients were grouped into quartiles according to baseline CRP, ESR and BASDAI and four ASDAS groups. Trend analyses were performed using ANCOVA (AIx/PWV as dependent variable) with separate models for CRP, ESR, BASDAI and ASDAS (age and gender adjusted). Independent predictors of future AIx and PWV levels were identified in multivariate linear regression models. RESULTS: In total, 85 patients participated. Increasing baseline values of CRP, ESR and ASDAS were associated with elevated AIx on follow-up (p(trend) 0.01, 0.05 and 0.04, respectively). Similar non-significant patterns were seen for PWV. In the multivariate analyses, baseline CRP and ASDAS were independently associated with future elevated AIx (p=0.03 and0.02, respectively). In the multivariate PWV model, results for CRP and ASDAS were non-significant. CONCLUSIONS: Baseline CRP and ASDAS were associated with future elevated arterial stiffness measured as AIx, supporting that disease activity is related to future risk of cardiovascular disease in patients with AS.