Time trends in incidence, clinical features, and cardiovascular disease in ankylosing spondylitis over three decades: A population-based study

Objective To determine trends in the incidence and clinical presentation of ankylosing spondylitis (AS), the incidence of cardiovascular disease (CVD), and cardiovascular (CV) risk factors among patients with AS and compare the observed incidence of CVD with that predicted by the Framingham Risk Score (FRS). Methods A population-based inception cohort of residents of Olmsted County, Minnesota age ≥18 years who fulfilled Modified New York Criteria for AS in 1980-2009 was assembled. Clinical features at presentation were recorded. Age- and sex-adjusted incidence rates and survival were estimated. Incident CVD and CV risk factors were identified. The 10-year CVD risk was calculated using the FRS. Standardized incidence ratios (ratios of observed CVD in AS to that predicted by the FRS) were calculated. Results Eighty-six patients were diagnosed with AS over the study period with an age- and sex-adjusted incidence of 3.1 per 100,000 (95% confidence interval [95% CI] 2.5-3.8). The mean age at diagnosis was 35 years (range 19-69 years). Inflammatory back pain, seen in 90% of patients, was the most common presenting manifestation. The 10-year mean±SD cumulative incidence of CVD was 15.8%±6.1%, three times higher than the predicted events based on the FRS (standardized incidence ratio 3.01, 95% CI 1.35-6.69; P=0.007). Overall survival was similar to the general population. Conclusion AS occurs in approximately 3 persons per 100,000 per year. Clinical features, extraarticular manifestations, and interval from symptom onset to diagnosis have remained constant in this population over the study period. The CVD risk in these patients is higher than expected and underestimated by the FRS.