Studies Say Vitamin D Deficiency Doesn't Increase Odds of RA, But May Worsen OA Symptoms

OCTOBER 28, 2013
Katie Eder
In light of the growing evidence on immunoregulatory properties of vitamin D in suppressing autoimmunity, previous reports have described a link between vitamin D deficiency and an increased risk of rheumatoid arthritis (RA) development. However, a trio of studies presented at the American College of Rheumatology 2013 Annual Meeting in San Diego, CA, has now offered clinical support to the contrary belief.
In the first study, which was presented during a poster session on the human etiology and pathogenesis of RA, Jonida Cote, DO, and colleagues from the Division of Rheumatology at Geisinger Health System in Danville, PA, matched 270 incident RA patients to 1,341 control subjects by age and gender using electronic health records (EHR) in order to evaluate the association of vitamin D levels with RA.
According to the researchers, “vitamin D levels were treated both as continuous and categorical; we used <30 IU as the primary cutoff, but also used <20 IU to investigate the RA association with severe vitamin D deficiency.” Among all RA patients and matched controls, the median age was 62.4 years old and the median vitamin D level was 31 IU. 
At the conclusion of their analysis — which adjusted for obesity and current smoking status and was powered at 82% to detect an odds ratio (OR) of 1.5 — Cote and her co-authors determined that “low vitamin D level was not associated with increased odds for incident RA,” as both rheumatoid factor-positive patients and rheumatoid factor-negative patients with vitamin D levels below 30 IU were not at an increased risk of developing RA (Table 1). 

However, Cote said during the poster session that she was puzzled by the fact that male patients with vitamin D levels below 20 IU were less likely to develop RA compared to their male counterparts with higher vitamin D levels of up to 30 IU, though she attributed those peculiar results to the small size of the male RA case cohort (n= 45).

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