Background/Purpose: Patients with rheumatoid arthritis (RA) are at high risk of developing vertebral fractures. Previously, utilizing data from our Institute of Rheumatology Rheumatoid Arthritis (IORRA) cohort study, we reported clinical risk factors for clinicalvertebral fractures in Japanese patients with RA. However, in our previous studies, which analyzed data from 2000 to 2005, the number of patients with verified clinical vertebral fractures was only 40. The aim of this study was to re-evaluate the associations between potential risk factors and the occurrence of clinical vertebral fractures in a larger number of Japanese patients with RA.

Methods: IORRA is a prospective observational cohort study of Japanese patients with RA established in 2000 at the Institute of Rheumatology, Tokyo Women’s Medical University. A total of 10,240 Japanese patients with RA  (82% female; mean age, 56 years) were enrolled in IORRA cohort study from 2000 to 2011. Self-reported vertebral fractures were verified with patient medical records and radiographs. Independent contributions of various risk factors to clinical vertebral fracture occurrence were analyzed with Cox proportional hazards models.

Results: During a mean follow-up of 4.9 years, 399 patients reported 638 clinical vertebral fractures. Among these patients, 187 clinical vertebral fractures in 187 patients (18 men, 169 women) were verified with medical records (n = 95) and radiographs (n =92). The vertebral fractures were mainly caused by spontaneous events (65%) and falls (25%). Vertebral fractures occurred at lumbar (36%), thoracic (37%), and both (27%) levels of the spine. In men with RA, multivariate Cox regression analyses estimated that the risk of sustaining a clinical vertebral fracture increased by 2.51 for every 10 years of increased age, 2.96 for Japanese version of Health Assessment Questionnaire-Disability Index (J-HAQ-DI), and 1.17 for daily prednisolone dose (Table 1). In women with RA, multivariate Cox regression analyses estimated that the risk of sustaining a clinical vertebral fracture increased by 1.30 for Disease Activity Score 28 (DAS28), 2.35 for history of any previous fractures, 1.67 for every 10 years of increased age, 1.39 for J-HAQ-DI, and 1.08 for daily prednisolone dose (Table 1). Among the eight domains of the J-HAQ-DI, J-HAQ-DI (arising) was significantly associated with the clinical vertebral fractures in Japanese patients with RA (hazard ratio 1.26, 95% confidence interval [CI] 1.02-1.54).

Conclusion: We confirmed the associations between clinical vertebral fractures and advanced age, J-HAQ-DI, and high daily prednisolone dose in a larger number of patients and found significant correlations between clinical vertebral fractures and DAS28, history of any previous fractures, and J-HAQ-DI (arising) in Japanese patients with RA. These clinical risk factors  appear to be different between men and women in Japanese RA patients.

Table 1. Hazard ratios (95% confidence interval) for the occurrence of clinical vertebral fractures in Japanese men and women with RA: Multivariate analyses.

Risk factors	Men	Women
DAS28	0.73 (0.36-2.48)	1.30 (1.05-1.63)
History of any prior fracture	1.32 (0.45-3.81)	2.35 (1.69-3.27)
Age, per 10 years	2.51 (1.34-4.73)	1.67 (1.42-1.97)
Japanese HAQ-DI	2.96 (1.02-3.60)	1.39 (1.08-1.79)
Daily prednisolone dose, mg/day	1.17 (1.06-1.29)	1.08 (1.05-1.12)

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/risk-factors-for-clinical-vertebral-fractures-in-japanese-men-and-women-with-rheumatoid-arthritis-results-from-a-large-prospective-observational-cohort-study/