People with systemic lupus erythematosus (SLE) have vitamin D deficiency — and living in Asia, South America, or Africa are among the risk factors, according to a review study.
Not receiving vitamin D supplements also is a risk factor increasing this deficiency, the findings showed.
The research, “Vitamin D status in patients with systemic lupus erythematosus (SLE): A systematic review and meta-analysis,” appeared in the journal Autoimmunity Reviews.
Vitamin D has been increasingly reported to have immunomodulatory effects. Similar to other autoimmune diseases, vitamin D deficiency has been associated with SLE, possibly the result of patients avoiding sunlight exposure due to their photosensitivity. However, existing evidence is still contradictory.
Aiming to better understand this link, a team from Malaysia, Bangladesh, and Poland conducted a systematic review of four online databases — up through March 2 — and a meta-analysis. A meta-analysis is a statistical assessment combining the results of several studies.
The researchers included 34 studies from 14 countries across six continents, published between 1999 and 2018. This represented a total of 2,265 adults with SLE — mean age 27.8 to 49.2 years — and 1,846 healthy people (controls). Mean disease duration ranged from 2 to 15.5 years.
The results showed that serum levels of vitamin D were significantly lower in patients with SLE than in the controls (20.7 vs. 31.4 ng/mL), regardless of body mass index.
The researchers noted that reduced vitamin D levels specifically were found in patients from Asia, South America, and Africa, as well as in people with SLE living below the 37-degree latitude line. Countries with evidence of vitamin D deficiency in SLE included Brazil, Egypt, Indonesia, and China — all places with significant monthly sunshine.
Use of sunscreens, taking sun protective measures, and using Islamic veils are among potential reasons for lower vitamin D levels in such countries, the scientists said.
The data also showed that these levels were lower during the summer, but not during winter, “possibly due to the tendency of avoiding sun during the summer season,” the team said.
Other factors increasing the likelihood of vitamin D deficiency were not receiving supplements of the vitamin, and treatment with hydroxychloroquine, corticosteroids, or immunosuppressants without such Vitamin D supplements.
The researchers noted that the analysis found that the vast majority (91.2%) of the included studies were of high methodological quality.
“Inadequate levels of serum vitamin D is significantly high in patients with SLE compared to healthy subjects,” the scientists said. Given those results, for people with SLE, “vitamin D supplementation with regular monitoring should be considered as part of their health management plans.”