Survival benefit of statin use in ankylosing spondylitis: a general population-based cohort study

Objectives: Recent studies have shown an increase in both cardiovascular and all-cause mortality in ankylosing spondylitis (AS). We examined the potential survival benefit of statin use in AS within a general population context.

Methods: We performed an incident user cohort study with time-stratified propensity score matching using a UK general population database between 1 January 2000 and 31 December 2014. To account for potential confounders, we compared propensity score-matched cohorts of statin initiators and non-initiators using 1-year cohort accrual blocks. The variables used to create the propensity score model included disease duration, body mass index, lifestyle factors, comorbidities and medication use.

Results: Using unmatched AS cohorts, statin initiators (n=1430) showed a 43% higher risk of mortality than non-initiators (n=1430) (HR=1.43; 95% CI 1.12 to 1.84). After propensity score matching, patients with AS who initiated statins (n=1108) had 96 deaths, and matched non-initiators (n=1108) had 134 deaths over a mean follow-up of 5.3 and 5.1 years, respectively. This corresponded to mortality rates of 16.5 and 23.8 per 1000 person-years (PY), respectively, resulting in an HR of 0.63 (95% CI 0.46 to 0.85) and an absolute mortality rate difference of 7.3 deaths per 1000 PY (95% CI 2.1 to 12.5).

Conclusion: This general population-based cohort study suggests that statin initiation is associated with a substantially lower risk of mortality among patients with AS. The magnitude of the inverse association appears to be larger than that observed in randomised trials of the general population and in population-based cohort studies of patients with rheumatoid arthritis.