Incidence Rate and Factors Associated With Fractures Among Medicare Beneficiaries With Ankylosing Spondylitis in the United States

ObjectiveWe evaluated the incidence rate and factors associated with fractures among adults with ankylosing spondylitis (AS).MethodsWe performed a retrospective cohort study with data from the Rheumatology Informatics System for Effectiveness registry linked to Medicare claims from 2016 to 2018. Patients were required to have two AS International Classification of Diseases codes 30 or more days apart and a subsequent Medicare claim. Then, 1 year of baseline characteristics were included, after which patients were observed for fractures. First, we calculated the incidence rate of fractures. Second, we constructed logistic regression models to identify factors associated with the fracture, including age, sex, race and ethnicity, body mass index, Medicare/Medicaid dual eligibility, area deprivation index, Charlson comorbidity index, smoking status, osteoporosis, historical fracture, and use of osteoporosis treatment, glucocorticoids, and opioids.ResultsWe identified 1,426 adults with prevalent AS. Mean +/- SD age was 69.4 +/- 9.8 years, 44.3% were female, and 77.3% were non-Hispanic White. Fractures occurred in 197 adults with AS. The overall incidence rate of fractures was 76.7 (95% confidence interval [CI] 66.4-88.6) per 1,000 person-years. Older age (odds ratio [OR] 2.8, 95% CI 1.39-5.65), historical fracture (OR 5.24, 95% CI 3.44-7.99), and use of more than 30 mg morphine equivalent (OR 1.86, 95% CI 1.08-3.19) conferred increased odds of fracture.ConclusionsIn this large sample of Medicare beneficiaries with AS, increasing age, historical fracture, and use of opioids had higher odds of fracture. Men and women were equally likely to have a fracture. Because opioid use was associated with fracture in AS, this high-risk population should be considered for interventions to mitigate risk.