Higher Concentrations of Vitamin D in Canadian Children with Juvenile Idiopathic Arthritis Compared to Healthy Controls Are Associated with More Frequent Use of Vitamin D Supplements and Season of Birth.

A number of studies have demonstrated that patients with autoimmune disease have lower levels of vitamin D prompting speculation that vitamin D might suppress inflammation and immune responses in children with juvenile idiopathic arthritis (JIA). The objective of this study was to compare vitamin D levels in children with JIA at disease onset with healthy children. We hypothesized that children and adolescents with JIA have lower vitamin D levels than healthy children and adolescents. Data from a Canadian cohort of children with new-onset JIA ( n = 164, data collection 2007-2012) were compared to Canadian Health Measures Survey (CHMS) data ( n = 4027, data collection 2007-2011). We compared 25-hydroxy vitamin D (25(OH)D) concentrations with measures of inflammation, vitamin D supplement use, milk intake, and season of birth. Mean 25(OH)D level was significantly higher in patients with JIA (79 +/- 3.1 nmol/L) than in healthy controls (68 +/- 1.8 nmol/L P < .05). Patients with JIA more often used vitamin D containing supplements (50% vs. 7%; P < .05). The prevalence of 25(OH)D deficiency ( < 30 nmol/L) was 6% for both groups. Children with JIA with 25(OH)D deficiency or insufficiency ( < 50 nmol/L) had higher C-reactive protein levels. Children with JIA were more often born in the fall and winter compared to healthy children. In contrast to earlier studies, we found vitamin D levels in Canadian children with JIA were higher compared to healthy children and associated with more frequent use of vitamin D supplements. Among children with JIA, low vitamin D levels were associated with indicators of greater inflammation. (c) 2021 Elsevier Inc. All rights reserved.