Incident Spine Surgery in Patients With Ankylosing Spondylitis: A Secondary Cohort Analysis of a Nationwide, Population-Based Health Claims Database.

Abstract

To evaluate the risk of the need for spine surgery, including cervical and lumbar spine surgeries in patients with ankylosing spondylitis (AS), compared with those without the disease. A secondary data analysis was conducted using population-based claims data from the Taiwan National Health Insurance Research Database. Adult patients with newly diagnosed AS between January 2000 and December 2012 were identified based on the International Classification of Diseases, Ninth Revision, Clinical Modification code 720.0. A comparison cohort was assembled using frequency-matched sex, 10-year age intervals, and index year with the AS cohort at a ratio of 5:1. All patients were followed until our study outcomes (any spine surgery, cervical spine surgery, and lumbar spine surgery), based on surgical codes, had occurred, or until the end of the followup period. Incidence rate ratios (IRRs) were calculated using Poisson regression models. We identified 3,462 patients with AS and 17,310 patients without AS. All 3 outcome variables were seen at a significantly higher incidence in the AS cohort than in the comparison cohort (IRR 2.34 [95% confidence interval (95% CI) 1.92-2.87] for any spine surgery, IRR 2.36 [95% CI 1.55-3.59] for cervical spine surgery, and IRR 2.33 [95% CI 1.85-2.93] for lumbar spine surgery). Moreover, the magnitudes of the IRRs were the largest in the youngest age group (individuals in their 20s and 30s). Patients with AS, particularly those in their 20s and 30s, had a significantly higher risk of needing any spine surgery, cervical spine surgery, and lumbar spine surgery, compared with patients without AS.