In a surprise finding, researchers out of Finland have found that active juvenile idiopathic arthritis is associated with higher vitamin D levels compared to inactive juvenile idiopathic arthritis.
Juvenile idiopathic arthritis (JIA) is characterized by inflammation in the joints, usually in the hands, feet, and knees. JIA is thought to be an autoimmune disease and is prevalent in about 50,000 children in the United States.
Few studies have looked at vitamin D and JIA. There is, however, lots of research to date on the relationship between vitamin D and other autoimmune diseases, with researchers finding an association between vitamin D deficiency and higher risk of multiple sclerosis, lupus, Crohn’s and type I diabetes. So researchers wanted to know if vitamin D deficiency might also be linked with JIA somehow.
In the present study, researchers looked at vitamin D levels of JIA patients. Each patient had either oligoarthritis or polyarticular arthritis. Oligoarthritis affects four or fewer joints and commonly occurs in the knee and wrist joints. Polyarticular arthritis affects five or more joints and is found in the hands, knees, hips, ankles, feet, and neck. Additionally, polyarticular arthritis is more common in girls than boys.
The researchers looked at the vitamin D levels of the JIA patients and looked at what type of JIA they had and whether or not their JIA was currently active or inactive. They wanted to know, was there a correlation between vitamin D levels and whether or not their condition was active? Inactive JIA was classified as a previous diagnosis of JIA but with no current active arthritis, fever, or rash.
So they looked at blood samples from 1997-2001 of 136 Finnish JIA patients under the age of 18. The researchers found:
- The difference in average vitamin D levels for those with polyarticular JIA and oligoarticular JIA was not significant, with respective levels of 24.5 ng/ml and 25.8 ng/ml (p=0.33).
- After adjusting for confounding factors, females with polyarticular JIA had significantly lower vitamin D levels than males with polyarticular JIA (p= 0.02).
- Those with active JIA had an average vitamin D level of 26 ng/ml compared with inactive JIA, who had an average level of 22.8 ng/ml (p=0.03).
These results were particularly surprising because patients with active JIA take glucocorticoids as treatment. Glucocorticoid use is associated with lower vitamin D levels, as opposed to the higher levels found in the study.
One explanation for the surprise finding may be that the patients receiving glucocorticoids were also receiving vitamin D supplementation, leading to higher levels. However, since no data was collected on vitamin D supplement use, the researchers weren’t able to say for sure if this was the case.
The researchers call for future studies that include a larger sample size looking at new-onset JIA with more information on vitamin D intake and disease activity.