Effect of Vitamin D Supplementation on Bone Mineral Density in Rheumatoid Arthritis Patients With Osteoporosis

Objectives:To assess the effect of vitamin D supplementation on bone mineral density (BMD) in rheumatoid arthritis (RA) patients with osteoporosis and determine whether supplementation of more than 800 IU/day, which is the currently recommended dose, is beneficial. Methods:RA patients with osteoporosis who received bisphosphonate were included. Patients were classified into four groups according to the dose of vitamin D supplementation (0, 400, 800, and >= 1,000 IU/day). Multivariable linear regression models were performed to evaluate the effect of each dose of vitamin D supplementation on 1-year% change of BMD. Results:In total, 187 RA patients with osteoporosis were included. In the multivariate model adjusted for potential confounders, patients receiving vitamin D supplementation had a significantly higher increase in 1-year % change in lumbar spine BMD (400 IU/day: beta = 2.51 [95% CI: 0.04-4.99], 800 IU/day: beta = 2.90 [95% CI: 0.47-5.33], and >= 1,000 IU/day: beta = 6.01 [95% CI: 3.71-8.32]) and femoral neck BMD (400 IU/day: beta = 3.88 [95% CI: 1.83-5.94], 800 IU/day: beta =4.30 [95% CI: 2.25-6.35], and >= 1,000 IU/day: beta = 6.79 [95% CI: 4.87-8.71]) than those not receiving the supplementation. Notably, the >= 1,000-IU/day group had a significantly higher increase in 1-year % change in lumbar spine BMD (beta = 3.11 [95% CI: 0.86-5.37]) and femoral neck BMD (beta = 2.50 [95% CI: 0.63-4.36]) than the 800-IU/day group. Conclusion:In RA patients with osteoporosis receiving bisphosphonates, vitamin D supplementation was associated with a higher increase in BMD. This effect was higher in the vitamin D supplementation dose of >= 1,000 IU/day than in 800 IU/day.