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FRI0381 Increased risk of osteoporotic fractures in adult patients with polymyositis and dermatomyositis: a nationwide population-based cohort study
  1. C-C Lai1,
  2. W-S Chen1,
  3. Y-P Tsao1,
  4. Y-S Chang2
  1. 1Division of Allergy, Immunology, and Rheumatology, Taipei Veterans General Hospital, Taipei City
  2. 2Division of Allergy, Immunology and Rheumatology, Department of Internal Medicine, Shuang Ho Hospital, Taipei Medical University, New Taipei City, Taiwan, Province of China

Abstract

Background Patients with polymyositis and dermatomyositis (PM/DM) are characterized by chronic muscle weakness due to autoimmune-mediated myositis and are usually treated with corticosteroids initially. PM/DM patients prone to develop osteoporosis and subsequent fractures but are rarely investigated.

Objectives To explore the incidence rate (IR) and risk factors of osteoporotic fractures (OFs) among adult PM/DM patients.

Methods We conducted a cohort study by utilizing the Taiwan National Health Insurance database. PM/DM patients and respective age- and gender-matched cohort without PM/DM were enrolled. The primary endpoint was the initial event of OFs. We used the Cox proportional hazard model to study the risk factors of OFs in the PM/DM cohort.

Results Among 2391 PM/DM patients (67.8% female, mean age: 49.5 years) followed for a mean (SD) of 6.1 (5.0) years, 116 developed vertebral fractures, 32 had hip fractures, and 14 experienced radius fractures (IR: 8.18, 2.20, and 0.96 per 1000 person-years, respectively, Table 1). Compared with the matched cohort, the PM/DM patients had higher IR ratios (IRRs) (95% CIs) of OFs at all age groups at enrollment: 3.27 (2.19 to 4.81, p<0.0001) for people <50 years and 2.29 (1.85 to 2.82, p<0.0001) for those ≥50 years. The IRRs were 2.39 (1.92 to 2.94, p<0.0001) for vertebral fractures and 1.62 (1.07 to 2.38, p=0.0093) for hip fractures. PM/DM patients experienced vertebral fractures and hip fractures at younger ages (62.2 vs 68.4 and 66.0 vs 75.4 years, respectively; both p<0.001). Multivariable Cox regression analyses showed that being female gender, age ≥50 years, having hypertension, coronary artery disease, asthma, and using daily prednisolone equivalent to >5 mg are associated with OFs.

Table 1.

IRs and IRRs of osteoporotic fractures: overall and subgroup analysis

Conclusions Adult PM/DM patients had a high IR of vertebral and hip fractures. Patients who were female, advanced age, having certain comorbidities, and exposed to corticosteroid exhibited a higher risk.

Disclosure of Interest None declared

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