Vitamin D deficiency is a risk factor for new fractures in Japanese postmenopausal women with rheumatoid arthritis: results from the IORRA cohort study

In this study, we assess the association between the occurrence of new fractures and vitamin D deficiency in Japanese patients with rheumatoid arthritis using our large IORRA cohort. The results suggest that vitamin D deficiency is a significant risk factor for new fractures in Japanese female patients over the age of 50 years with rheumatoid arthritis. Purpose Both rheumatoid arthritis (RA) and menopause are known risk factors for the onset of osteoporosis. The occurrence of new clinical fractures in patients with RA can significantly lower quality of life. The purpose of this study was to investigate whether vitamin D deficiency in Japanese women with RA could be a risk factor for new fractures. Methods Between 2011 and 2017, a total of 2567 female patients with RA over the age of 50 years (mean age, 65.9 years) were enrolled in a prospective observational study. Self-reported occurrences of new fractures were verified using patient medical records. Vitamin D deficiency was defined as serum 25(OH)D levels < 20 ng/mL. Cox proportional hazards models were used to analyze the independent contributions of various risk factors to the occurrence of a new fracture. Results New clinical fractures were sustained by 205 patients in the included cases. Among them, new osteoporotic fractures were sustained by 139 patients (63 vertebral fractures and 76 non-vertebral fractures). Among all patients, the mean (SD) serum 25(OH)D level was 16.9 (5.89) ng/mL and the prevalence of vitamin D deficiency was 72.6%. A Cox proportional hazards model revealed that vitamin D deficiency was significantly associated with all new clinical fractures (hazard ratio, 1.44 [95% confidence interval 1.02-2.05]; p = 0.0365) and all new osteoporotic fractures (hazard ratio, 1.75 [95% confidence interval 1.14-2.69]; p = 0.0109). Conclusion Vitamin D deficiency is a risk factor for new fractures in Japanese female patients over the age of 50 years with RA. Screening these patients for serum 25(OH)D could potentially be seminal to reducing their risk of fractures.