FRI0310 HIGHER RISK OF INCIDENT FRACTURE IN PATIENTS WITH ANKYLOSING SPONDYLITIS COMPARED TO THE GENERAL POPULATION
Authors: K. Bengtsson, J. Askling, M. Lorentzon, B. Rosengren, A. Deminger, E. Klingberg, L. T. H. Jacobsson, H. Forsblad-D’elia
Journal: Annals of the Rheumatic Diseases (2020)

Background: Ankylosing spondylitis (AS) is characterized by pathologic new bone formation and bone loss. Vertebral fracture (VF) is a known complication of AS, whereas the risk of other major osteoporotic fractures (MOFs) is less studied. Objectives: To estimate incidence rates (IRs) of incident fractures (any, VF and other MOF (humerus, forearm and hip)) in patients with AS compared to controls from general population. Methods: This is a nationwide, register-based and observational cohort study including patients diagnosed with AS (n=11611, 65% men, mean age 48 years) identified in the National patient register (NPR) 2001 through 2015, and age- and sex-matched controls (n=58050) from the Swedish Population Register. The study period started 1 January 2007 or 3 months after the first AS diagnosis, whichever came later, and ended at the first occurrence of each fracture outcome (identified in the NPR), death, emigration or 31 December 2016. Patients and controls with any prior fracture in NPR within a 6-year period before start of the study period were not included. Any fracture (except skull and phalangeal fractures), VF and other MOF were identified in NPR according to pre-specified ICD codes. Each fracture outcome was analysed separately. Poisson regression was used to calculate IRs and incidence rate ratios (IRRs), overall and stratified by sex. Kaplan-Meier curves were plotted. Results: In total 807 (7.0%) of patients with AS and 3201 (5.5%) of matched controls had a history of prior fracture within a 6-year period, and were excluded from further analyses. We noted higher IRs for any fracture, VF and other MOF in AS vs controls, see Figure for Kaplan-Meier curves and Table for IRs and IRRs. In sex-stratified analyses, men with AS (vs. male controls) had a higher relative risk for all fracture outcomes, whereas among women with AS (vs. female controls), a higher relative risk was demonstrated for any fracture and VF. 5-year cumulative incidence for any fracture, VF and other MOF was 6.2%, 1.6% and 1.7%, respectively in AS and 4.3%, 0.3% and 1.2%, respectively in controls. Figure. Kaplan-Meier curves. A) Vertebral fractures B) Other MOF (humerus, hip, forearm) Conclusion: Patients with AS have a higher risk of any fracture, VF and other MOF compared to general population. This was especially pronounced for VF in both sexes and for hip fracture in men with AS. Table. IRs, presented as number of events per 1000 person-years at risk, and IRRs for each fracture outcome. AS Controls AS vs Controls Event IR (95% CI) Event IR (95% CI) IRR (95% CI) Any fracture 1060 14.9 (14.1 to 15.9) 3605 10.5 (10.2 to10.9) 1.4 (1.3 to 1.5) -Men 685 14.6 (13.5 to 15.7) 2282 10.1 (9.7 to 10.5) 1.4 (1.3 to 1.6) -Women 375 15.6 (14.1 to 17.3) 1323 11.3 (10.7 to 12.0) 1.4 (1.2 to 1.5) Vertebral fractures 277 3.7 (3.3 to 4.2) 328 0.9 (0.8 to 1.0) 4.1 (3.5 to 4.8) -Men 206 4.2 (3.7 to 4.8) 230 1.0 (0.9 to 1.1) 4.3 (3.6 to 5.2) -Women 71 2.8 (2.2 to 3.5) 98 0.8 (0.7 to 1.0) 3.5 (2.6 to 4.7) MOF (humerus, hip, forearm) 311 4.2 (3.8 to 4.7) 1105 3.1 (2.9 to 3.3) 1.3 (1.2 to 1.5) -Men 176 3.6 (3.1 to 4.2) 540 2.3 (2.1 to 2.5) 1.5 (1.3 to 1.8) -Women 135 5.4 (4.6 to 6.4) 565 4.7 (4.3 to 5.2) 1.1 (0.9 to 1.4) MOF humerus 78 1.0 (0.8 to 1.3) 283 0.8 (0.7 to 0.9) 1.3 (1.0 to 1.7) -Men 42 0.8 (0.6 to 1.1) 137 0.6 (0.5 to 0.7) 1.5 (1.0 to 2.1) -Women 36 1.4 (1.0 to 2.0) 146 1.2 (1.0 to 1.4) 1.2 (0.8 to 1.7) MOF hip 93 1.2 (1.0 to 1.5) 260 0.7 (0.6 to 0.8) 1.7 (1.4 to 2.1) -Men 70 1.4 (1.1 to 1.8) 173 0.7 (0.6 to 0.9) 1.9 (1.5 to 2.5) -Women 23 0.9 (0.6 to 1.4) 87 0.7 (0.6 to 0.9) 1.3 (0.8 to 2.0) MOF forearm 156 2.1 (1.8 to 2.4) 631 1.8 (1.6 to 1.9) 1.2 (0.99 to 1.4) -Men 73 1.5 (1.2 to 1.9) 262 1.1 (1.0 to 1.3) 1.3 (1.0 to 1.7) -Women 83 3.3 (2.7 to 4.1) 369 3.1 (2.8 to 3.4) 1.1 (0.8 to 1.4) Disclosure of Interests: Karin Bengtsson: None declared, Johan Askling Grant/research support from: JA acts or has acted as PI for agreements between Karolinska Institutet and the following entities, mainly in the context of the ARTIS national safety monitoring programme of immunomodulators in rheumatology: Abbvie, BMS, Eli Lilly, Merck, MSD, Pfizer, Roche, Samsung Bioepis, Sanofi, and UCB Pharma, Mattias Lorentzon Consultant of: Lecture or consulting fees from Amgen, Lilly, UCB Pharma, Radius Health, Renapharma, Meda, GE-Lunar, Consilient Health, and Tromp Medical., Björn Rosengren: None declared, Anna Deminger: None declared, Eva Klingberg Grant/research support from: Roche, Consultant of: Novartis, Speakers bureau: Eli Lilly, Lennart T.H. Jacobsson Consultant of: AbbVie, Eli Lilly, Janssen, Novartis and Pfizer, Helena Forsblad-d’Elia Grant/research support from: Unrestricted grant from Novartis., Consultant of: Advisory Board Fees from Sandoz, Novartis, and Abbvie