First fracture in rheumatoid arthritis: analysis by fracture site, gender, age, and comorbidities.

Abstract

Rheumatoid arthritis (RA) is a potentially devastating disorder associated with increased risk of fractures, but current studies do not completely evaluate the RA fracture risk profile. This study estimates fracture incidence by site of fracture and makes comparisons between RA and controls using the key variables gender, age, and comorbidities.

Background: Rheumatoid arthritis RA is a potentially devastating osteoimmunological disorder, predisposing to osteoporosis (OP), fragility fracture (FF), and major osteoporotic fractures (MOF). As few studies incorporate statistical matching, comorbidity and non-MOF sites, we compared the incidence of first FF, MOF, and non-MOF in RA patients with a matched control cohort adjusting for comorbidities.

Methods: This longitudinal cohort study uses routinely collected administrative data from the West Australian Rheumatic Disease Epidemiological Registry (WARDER) between 1980 and 2015. RA patients, as defined using International Classification of Disease (ICD) codes, were compared to hospitalised patients free of rheumatic disease. Case-control matching adjusted for age, gender, and comorbidities (Charlson Comorbidity Index). Incidence rates (IR) per 1000 person years (PY) with 95% confidence intervals (CI) were compared by incidence rate ratios (IRR).

Findings: In RA patients from 2000 to 2010, the first fracture IR was 18.3 (15.7-21.2) for an IRR of 1.32 (1.10-1.60). Upper limb, lower limb, and axial IR were 5.56 (95% CI 4.18-7.26), 10.60 (95% CI 8.66-12.87), and 2.47 (95% CI 2.58-3.68) with IRR of 1.18 (95% CI 0.84-1.65), 1.44 (95% CI 1.19-1.86), and 1.01 (95% CI 0.61-1.63) respectively. The first fracture IR increased 6 years before first RA hospital record (RR 1.58, CI 1.05-2.39).

Conclusions: After age, gender, and comorbidity adjustment, RA is associated with a 32% higher incidence of first fracture, increased MOF, and a fracture incidence that is already increased before a first recorded RA diagnosis. This suggests a need for early attention to prevention of all fractures in RA patients.