Mortality in ankylosing spondylitis: results from a nationwide population-based study

OBJECTIVES: Information on mortality in ankylosing spondylitis (AS) is scarce. Our study therefore aimed to assess: (1) mortality in AS versus the general population, and (2) predictors of death in the AS population.

METHODS: Nationwide cohorts of patients with AS diagnosed at rheumatology or internal medicine outpatient clinics (n=8600) and age-matched, sex-matched and county-matched general population comparators (n=40 460) were identified from the National Patient Register and the census register, respectively. The follow-up period began on 1 January 2006 or at the first date of registered diagnosis thereafter and extended until death, emigration or 31 December 2012, whichever occurred first. Socioeconomic variables, AS-related clinical manifestations, joint surgery, comorbidities and medication were identified from other national registers. Cox regression models were used to determine mortality and predictors for death in the AS cohort.

RESULTS: There were 496 deaths in the AS cohort and 1533 deaths in the control cohort resulting in an age-adjusted and sex-adjusted HR of 1.60 (95% CI 1.44 to 1.77), with increased mortality for men (age-adjusted HR=1.53, 95% CI 1.36 to 1.72) and women (age-adjusted HR=1.83, 95% CI 1.50 to 2.22). Within the AS cohort, statistically significant predictors for death were a lower level of education, general comorbidities (diabetes, infections, cardiovascular, pulmonary and malignant diseases) and previous hip replacement surgery.

CONCLUSIONS: Mortality was increased for male and female patients with AS. Predictors of death within the AS cohort included socioeconomic status, general comorbidities and hip replacement surgery.