Background/Purpose: There are increasing data about vitamin D immunomodulatory potential in different rheumatologic disorders. Deficiency of vitamin D is frequent in patients with spondyloarthritis (SpA) but studies about the role of vitamin D in disease activity and functional impairment are controversial. This study aims to assess whether vitamin D deficiency is associated with increased disease activity and functional impairment in patients with SpA.

Methods: Our cross-sectional study included patients with SpA according to Assessment of Spondyloarthritis International Society classification criteria. All study patients were treated with biologic disease-modifying antirheumatic drug (bDMARD). Disease activity was assessed using Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) and Ankylosing Spondylitis Disease Activity Score (ASDAS) and functional impairment using Bath Ankylosing Spondylitis Functional Index (BASFI). Serum 25-hydroxyvitamin D [25(OH)D] levels were measured in SpA patients after 6 months of bDMARD therapy. Vitamin D deficiency was defined as 25(OH)D< 30ng/mL. Vitamin D deficient patients were compared with non-deficient patients using Student’s t-test for Gaussian.

Results: We included 190 patients with axial and peripheral SpA, 98 were females (51.6%) and 41 current smokers (21.6%). Mean age was 42.7±12.1 and mean disease duration 8.0±9.1 years. Non-steroidal anti-inflammatory drugs were used by 102 patients (53.7%). Seventy patients (36.8%) were treated with conventional syntheticDMARDs and all patients were on bDMARD therapy (189 patients with tumor necrosis factor inhibitors and one with interleukin-17 inhibitor. The mean concentration of 25(OH)D was 27.2±13.4 ng/ml and 118 patients (62.1%) had 25(OH)D levels below the recommended threshold (< 30 ng/ml). Vitamin D supplementation was used by 75 patients (39.5%). Subgroups analysis of SpA patients with low 25(OH)D concentration (< 30ng/ml) compared to higher 25(OH)D concentration show that mean BASDAI (4.28 vs 3.16), ASDAS (2.48 vs 2.09) and BASFI (4.82 vs 3.41) were all significantly higher in patients deficient for vitamin D (p< 0,05).

Conclusion: The group of patients with vitamin D deficiency has significantly higher levels of activity and functional impairment than the group of patients with normal vitamin D concentration. According to these data vitamin D can therefore play an immunomodulating and anti-inflammatory role and can be considered a co-adjuvant in the treatment of these patients.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/vitamin-d-deficiency-and-disease-activity-in-patients-with-spondyloarthritis/