Observational studies have shown that levels are inversely associated with disease activity, but population-based studies remain inconsistent

Methods: Information was collected from studies measuring visual analog scale (VAS) pain, disease activity score 28 (DAS28), serum vitamin D levels, tender joint count (TJC), swollen joint count (SJC), erythrocyte sedimentation rate (ESR), C-reactive protein (CRP).

Results: Six studies (n = 120) were included in the meta-analysis. Vitamin D supplementation resulted in significant improvements in DAS28 (95% weighted mean difference (p < 0.001), ESR 95% (p = 0.04), and painful joint count 95% (p = 0.03), but not in other outcomes. Subgroup analysis showed that VAS and serum vitamin D were improved across subgroups. TJC and serum vitamin D levels were improved in subgroups with treatment duration ≤ 12 days, while VAS and DAS28 in the subgroup with treatment duration > 12 days differed from those in the control group. At a vitamin D dose ≤50,000 IU, only serum vitamin D and TJC improved, while at a vitamin D dose > 50,000 IU, VAS and DAS28 improved.

Vitamin D, rheumatoid arthritis, C-reactive protein

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