Factors associated with decreasing serum 25(OH)D among Japanese patients with rheumatoid arthritis: Results from the IORRA cohort study

Abstract

Objective: The aim of this study was to investigate factors that predict a decrease in serum 25(OH)D among Japanese patients with rheumatoid arthritis (RA).Methods: In 2011 and 2013, serum 25(OH)D was evaluated in the same 2534 Japanese patients with RA (2179 women and 355 men) who participated in the Institute of Rheumatology Rheumatoid Arthritis (IORRA) cohort study. A vitamin D deficiency was defined as serum 25(OH)D levels <20 ng/mL. Predictive factors resulting in decreased serum 25(OH)D over a 2-year period were evaluated using multivariate logistic regression.Results: The prevalence of vitamin D deficiency was 73.3% in 2011 and 68.2% in 2013. Serum 25(OH)D levels decreased by >5 ng/mL from 2011 to 2013 in 224 (8.8%) patients. A serum 25(OH)D decrease of >5 ng/mL was significantly associated with female gender, younger age, and disuse of bisphosphonates among all patients, and younger age, higher Japanese health assessment questionnaire disability index (JHAQ-DI), increased tender joint counts, and disuse of bisphosphonates and/or active vitamin D3 among women with RA.Conclusion: Female gender, younger age, JHAQ-DI, tender joint counts, and disuse of bisphosphonates and/or active vitamin D3 appear to be associated with a decrease in serum 25(OH)D in Japanese patients with RA.