Relationship between serum vitamin D level and severity of rheumatoid arthritis

Background: Recent studies have suggested a relation between vitamin D serum level and autoimmune diseases including rheumatoid arthritis (RA). Also, vitamin D has an important role in regulating the immune system. Objective: The present study aimed at exploring the relation between serum level of vitamin D and severity of RA. Methods: The study group consisted of 153 RA patients not on vitamin D supplements who had referred to Qazvin Avicenna Hospital. Disease activity was assessed according to the disease activity score28 (DAS28). Serum levels of vitamin D and Erythrocyte Sedimentation Rate (ESR) were determined for all the participants. Findings: Vitamin D deficiency was found in 105 RA patients (68.6%). Patients were divided into three groups of low, moderate and high disease activity according to DAS28 score with 86 (56.2%), 33 (21.5%) and 34 (22.2%) patients respectively. A significant negative correlation was found between serum level of vitamin D and disease severity according to DAS28. Similarly, a negative correlation was shown to exist between the patients' pain intensity according to VAS score, and their ESR serum level (P<0.05). Conclusion: Vitamin D deficiency was prevalent among patients with RA. Furthermore, there was a negative correlation between vitamin D and the disease severity.