Vitamin D and rheumatoid arthritis

Abstract

Objectives: Vitamin D deficiency has been implicated in the pathogenesis of autoimmune diseases, such as diabetes mellitus type 1 and multiple sclerosis. Reduced vitamin D intake has been linked to increased susceptibility to the development of rheumatoid arthritis (RA) and vitamin D deficiency has been found to be associated with disease activity in patients with RA. The objective was to evaluate vitamin D status in patients with RA and to assess the relationship between vitamin D levels and disease activity. Methods: In a cohort of 44 patients with RA, 25-hydroxyvitamin D3 [25(OH)D3] levels, parathyroid hormone levels, C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) were measured. Disease activity was evaluated by calculating the 28-joint Disease Activity Score (DAS28). A control group ( n = 44), matched for age and sex, was evaluated as well. Results: In the cohort of 44 patients with RA 25(OH)D3 levels were found to be low compared with the control group, 25(OH)D3 being 15.26 ± 1.07 ng/ml [mean ± standard error of the mean (SEM)] and 25.8 ± 1.6 ng/ml in the patient and control group respectively (Student’s t test, p < 0.001). Parathyroid hormone levels were 71.08 ± 7.02 pg/ml (mean ± SEM) (normal values 10.0–65.0 pg/ml), CRP 7.6 ± 1.57 mg/litre (mean ± SEM) (normal values < 3 mg/litre) and ESR was 38.0 ± 4.6 mm/h (mean ± SEM) in the group of patients with RA. Levels of 25(OH)D3 were found to be negatively correlated to the DAS28, the correlation coefficient being −0.084. Levels of 25(OH)D3 were also found to be negatively correlated to CRP and ESR, the correlation coefficient being –0.115 and −0.18, respectively. Conclusion: It appears that vitamin D deficiency is highly prevalent in patients with RA, and that vitamin D deficiency may be linked to disease severity in RA. As vitamin D deficiency has been linked to diffuse musculoskeletal pain, these results have therapeutic implications. Vitamin D supplementation may be needed both for the prevention of osteoporosis as well as for pain relief in patients with RA.