# Vitamin D as a Modifiable Risk Factor for Juvenile Idiopathic Arthritis: A Systematic Review and Meta-analysis of Observational Studies Comparing Baseline Vitamin D in Children with JIA to Individuals Without

## TL;DR

This study finds that children with juvenile idiopathic arthritis have lower vitamin D levels than healthy children, suggesting vitamin D may play a role in the disease.

## Contribution

The study provides a meta-analysis showing a significant association between lower vitamin D levels and juvenile idiopathic arthritis in children.

## Key findings

- Children with JIA had significantly lower vitamin D levels compared to controls.
- A random-effects model confirmed a standardized mean difference of -0.49 in vitamin D levels between JIA patients and controls.

## Abstract

The varying interactions contributing to the development of juvenile idiopathic arthritis (JIA) drive the struggle to understand its etiology. Among the environmental risk factors, vitamin D has been posited to have a component in disease progression, acting as an inflammatory mediator.

To investigate the correlation between serum 25-hydroxyvitamin D [25(OH)D] levels, indicative of vitamin D, among patients diagnosed with JIA compared with control participants. The aim was to elucidate potential therapeutic implications of vitamin D in the management of JIA.

A systematic search of 6 electronic databases (MEDLINE, Embase, Scopus, CINAHL, Web of Science, and Cochrane Library) was performed until February 2023. Inclusion criteria required participants to be <16 years old (either clinically diagnosed with JIA or a matched control participant), with vitamin D levels measured through serum laboratory methods. Exclusion criteria omitted studies in which participants used vitamin D supplementation or medications affecting vitamin D levels without corresponding statistical analyses on their association with vitamin D levels.

Each article was reviewed by at least 2 independent reviewers to assess eligibility for analysis.

Data were qualitatively analyzed to compare means of serum 25(OH)D levels (ng/mL) between patients with JIA and control participants, followed by a meta-analysis to obtain effect size.

Ten eligible studies were included qualitatively, and eight were included in the meta-analysis. Seven studies found a statistically significant difference in vitamin D levels between control participants and patients with JIA, with five of these reporting a lower mean vitamin D level in patients with JIA. A random-effects model using standardized mean difference found a statistically significant difference in vitamin D levels between control participants and patients with JIA (–0.49; 95% CI, –0.92 to –0.06).

The findings from the analysis indicate vitamin D levels were lower in patients with JIA as compared with healthy control participants at baseline. It is recommended that research into vitamin D supplementation and JIA should be conducted.