Background/Purpose Patients with RA are at increased risk of cardiovascular (CV) diseases, including acute coronary syndromes (ACS), deep venous thromboembolism (DVT) and pulmonary embolism (PE), and cerebrovascular diseases. Evidence suggests that traditional CV risk factors alone do not account for the entire risk increase. Instead, RA disease activity has been proposed to be of critical importance. Ankylosing Spondylitis (AS) is a chronic inflammatory disease with a different gender- and age-distribution, pathology, and phenotype yet often with a pronounced systemic inflammation. In contrast to the literature on CV risks in RA, data on CV risks in AS are less well studied, and because of the age/sex-differences between RA and AS, not directly comparable. The aim of this study was therefore to assess and compare CV risks, by CV phenotype, between prevalent patients with AS, RA and the general population, taking age and sex-differences into account.

Methods We performed a nationwide population-based cohort study based on register linkage of prospectively recorded data from the Swedish Patient, Death, and Population Registers 2006-2011. We identified one cohort of prevalent patients with RA (n=37,245), one with AS (N=5,358) and one with general population comparator subjects (n=185,153). These cohorts were followed through 2011 for first ever occurrence of ACS, DVT/PE, and stroke, respectively (individuals with a history of the outcome were excluded). Age- and sex-specific rates for each outcome were calculated; rates were then standardised to the age/sex-distribution of the AS cohort.

Results Crude rates were the lowest for AS. However, assuming all populations had the same age/sex distribution as the AS cohort, the rate for ACS was 30% higher among patients with AS, and 60% higher in patients with RA, than in the general population (Table). For stroke, the rate was 20% higher among patients with AS, and 30% higher in patients with RA, than in the general population. For thromboembolic events, the rate was 30% higher among patients with AS, and 80% higher in patients with RA, than in the general population.

Conclusion Prevalent patients with AS in a population-based cohort are at a 20-30% increased risk of CV events compared to the general population. Whilst increased, the level of increase is around half that seen in the corresponding age/gender groups in RA.

Table. Crude rates of ACS, stroke, and DVT/PE in AS, RA and general population cohorts, and the corresponding standardised rates using the AS population as standard.