Vitamina D e artrite reumatoide

Emerging evidence suggests that vitamin D plays an important role in immune regulation. Vitamin D receptors are found on several immune cells and in vitro studies have shown that vitamin D metabolites modulate T cell proliferation and dendritic cell function. Epidemiological data also imply that vitamin D deficiency may be a risk for development of autoimmune and other chronic diseases. Preliminary studies suggest that low levels of vitamin D may be common in rheumatoid arthritis (RA).It was reported an inverse relationship between vitamin D levels and disease activity and disability in patients with early inflammatory polyarthritis. Vitamin D deficiency is quite common among elderly individuals and it is associated with musculoskeletal symptoms. In rheumatoid arthritis (RA), its deficiency may be associated with increased disease activity and disability. We studied 1191 consecutive RA patients (85% women) from 22 Italian rheumatology centres. Together with parameters of disease activity, functional impairment, and mean time spent outdoor during summer months (sun exposure time), all patients had serum 25-hydroxyvitamin D [25(OH)D] and serum parathyroid hormone (PTH) levels measured in a centralized laboratory. Fifty five % of patients were not taking vitamin D supplements; the proportion of these patients with 25(OH)D level <20 ng/ml was 52%, and one third of those supplemented. In non-supplemented patients 25(OH)D levels were significantly correlated with Health Assessment Questionnaire Disability Index (HAQ), Mobility Activities of daily living score (ADL) , number of swollen joints. Significantly lower 25(OH)D values were found in patients not on disease remission or poorly responding to treatment, with the highest Steinbrocker functional state, and treated with disease-modifying antirheumatic drugs (DMARD). Body mass index (BMI) and sun exposure time were good predictors of 25(OH)D values (p>0.000). The patients with the worse indices of disease activity were spending significantly less time at sunshine. The association between disease activity scores or functional sores and 25(OH)D levels remained statistically significant even adjusting 25(OH)D levels for both sun exposure time and BMI. In conclusion, in RA patients disease activity and disability scores are inversely related with 25(OH)D levels. The causality of these associations must be confirmed by longitudinal studies aimed at evaluating the clinical response of disease activity to large vitamin D supplementations.