Vitamin D deficiency implicated in functional disability in RA
Vitamin D deficiency in patients with rheumatoid arthritis (RA) may contribute to functional disability but exerts no effect on disease activity or inflammatory markers, a recent study from Malaysia has found.
The study population comprised 100 RA patients (mean age, 48.2 years; 92 percent female) and 50 matched healthy controls (mean age, 45.2 years; 90 percent female). Researchers measured baseline serum 25(OH)D3 and interleukin (IL)-6 levels, as well as assessed Disease Activity Score of 28 joints and Health Assessment Questionnaire (HAQ) scores.
Sixty-three percent of RA patients and 76 percent of controls were vitamin D deficient (25[OH]D <50 nmol/L). In the RA group, significantly more Chinese patients had sufficient 25(OH)D3 levels than Malay and Indian patients (p<0.001 for both).
Serum 25(OH)D3 level inversely correlated with body mass index in RA patients (p=0.002) but not in controls (p=0.419).
All participants with vitamin D deficiency received loading doses of vitamin D3. There was no significant association observed between 25(OH)D3 levels and disease activity or serum IL-6 levels both at baseline and after treatment.
On the other hand, low serum 25(OH)D3 concentration was associated with functional disability at baseline, and vitamin D treatment yielded a 33-percent improvement in mean HAQ score (from 0.30 to 0.20).
The results suggest that vitamin D deficiency is prevalent in Malaysian RA patients and plays a role in functional disability. However, researchers admitted that the HAQ score reflects a subjective rather than an objective outcome measure and therefore could have been related to generalized musculoskeletal pain or chronic pain.
Additional studies are needed to confirm the role of vitamin D in mediating cytokines such as IL‐6 in the pathomechanism of RA, researchers added.