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The epidemiology of extra-articular manifestations in ankylosing spondylitis: a population-based matched cohort study
  1. Carmen Stolwijk1,2,3,
  2. Ivette Essers1,2,3,
  3. Astrid van Tubergen2,3,
  4. Annelies Boonen2,3,
  5. Marloes T Bazelier1,
  6. Marie L De Bruin1,
  7. Frank de Vries1,3,4,5
  1. 1Division of Pharmacoepidemiology and Clinical Pharmacology, Utrecht Institute for Pharmaceutical Sciences, Utrecht, The Netherlands
  2. 2Division of Rheumatology, Department of Medicine, Maastricht University Medical Center, Maastricht, The Netherlands
  3. 3Care and Public Health Research Institute (CAPHRI), Maastricht University, Maastricht, The Netherlands
  4. 4Department of Clinical Pharmacy and Toxicology, Maastricht University Medical Centre, Maastricht, The Netherlands
  5. 5MRC Lifecourse Epidemiology Unit, Southampton General Hospital, Southampton, UK
  1. Correspondence to Dr Frank de Vries, Division of Pharmacoepidemiology and Clinical Pharmacology, Utrecht Institute for Pharmaceutical Sciences, Utrecht University, Universiteitsweg 99, Utrecht 3584 CG, The Netherlands; f.devries{at}


Objective To assess the incidence and risks of common extra-articular manifestations (EAMs), that is, acute anterior uveitis (AAU), psoriasis and inflammatory bowel disease (IBD), in patients with ankylosing spondylitis (AS) compared with population-based controls.

Methods All incident patients with AS (n=4101) from the UK Clinical Practice Research Datalink (1987–2012) were matched with up to seven control subjects without AS by year of birth, sex and practice (n=28 591). Incidence rates, cumulative incidence rates and adjusted (adj) HRs for the development of EAMs were calculated, with time-dependent adjustments for age, sex, comorbidity and medication use.

Results At diagnosis of AS, the proportion of patients with an EAM was 11.4% for AAU, 4.4% for psoriasis and 3.7% for IBD. Incidence rates of EAMs were 8.9/1000 person-years for AAU, 3.4/1000 person-years for psoriasis and 2.4 /1000 person-years for IBD in AS. The 20-year cumulative incidence was 24.5%, 10.1% and 7.5%, respectively. Risks of EAMs were 1.5-fold to 16-fold increased versus controls, with an adj HR of 15.5 (95% CI 11.6 to 20.7) for AAU, adj HR of 1.5 (95% CI 1.1 to 1.9) for psoriasis and adj HR of 3.3 (95% CI 2.3 to 4.8) for IBD. For psoriasis and IBD, the highest risks were found in the 1st years after diagnosis, while developing AAU continued to be increased also 10 years after diagnosis of AS.

Conclusions The risk of, in particular AAU, but also of psoriasis and IBD, is significantly increased in patients with AS compared with controls. Hazard patterns are different for each of the EAMs.

  • uveitis
  • psoriasis
  • inflammatory bowel disease
  • epidemiology

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