25-hydroxyvitamin D levels and juvenile idiopathic arthritis: is there an association with disease activity?

The aims of this study were to examine the association between serum levels of 25-hydroxyvitamin D [25(OH)D] and disease activity in juvenile idiopathic arthritis (JIA), to determine the prevalence of vitamin D (VD) deficiency [25(OH)D ≤ 19 ng/ml] and insufficiency [25(OH)D 20-29 ng/ml], and to determine factors associated with lower serum levels of 25(OH)D in this population. In this cross-sectional study, disease activity was measured using JADAS-27, as well as its individual components (physician global assessment of disease activity, parent global assessment of child's well-being, count of joints with active disease, and erythrocyte sedimentation rate). Linear regression models were developed to analyze the association between serum 25(OH)D levels and JADAS-27 and to determine variables associated with serum 25(OH)D levels. A total of 154 patients (61% girls, 88% whites) were included. Mean age was 10.6. VD deficiency was detected in 13% and insufficiency in 42%. In univariate and multivariate analyses, 25(OH)D levels were not associated with JADAS-27, neither with its individual components. However, in a subset analysis including all new-onset JIA patients (n = 27), there was a nonsignificant negative correlation between serum 25(OH)D levels and JADAS-27 (r = -0.29, P = 0.14). In the univariate and multivariate analyses, age, ethnicity, BMI, and season were significantly associated with serum 25(OH)D levels, but not total VD intake. More than 1/2 of JIA patients had serum 25(OH)D levels below 29 ng/ml; however, there was no association between serum 25(OH)D levels and disease activity. Future larger, long-term studies with new-onset JIA patients are needed to further explore the association between serum 25(OH)D levels and disease activity.