A recent study published by the journal Lupus Science & Medicine found an inverse relationship between vitamin D status and disease activity in Australian patients with systemic lupus erythematosus.
Systemic lupus erythematosus (SLE) is an autoimmune condition, in which the immune system cannot differentiate between healthy tissue and foreign matter. This results in the body attacking healthy tissue, causing pain and inflammation.
Symptoms of SLE include but are not limited to skin rash, fatigue, photosensitivity, joint pain and fevers. The etiology behind SLE development is not fully understood. However, research indicates a combination of genetics, hormonal and environmental factors likely play a role.
Current research has shown a link between vitamin D status and SLE. However, there are no published studies that have evaluated the relationship between low vitamin D status and SLE disease activity in the Southern hemisphere.
A recent cohort study conducted in Melbourne, Australia aimed to determine if low vitamin D status is associated with higher SLE disease activity. They also wanted to see whether vitamin D supplementation is linked to reduced disease activity in SLE patients.
The researchers prospectively gathered data from 119 consecutive SLE patients who attended the Monash Medical Center Lupus Clinic between January 2007-2013.
All participants in the study met the American College of Rheumatology (ACR) criteria for SLE. The ACR criteria is a tool consisting of 11 common measures to assist physicians in diagnosing SLE. Serum vitamin D levels and SLE Disease Activity Index (SLEAI-2K) were measured at the time of the participant’s initial clinical visit and throughout a 12-month follow up. The SLEDAI-2K is a global index that assesses SLE disease severity, with a higher score indicating increased disease activity. Several other immune markers were measured, including erythrocyte sedimentation rate (ESR), which measures inflammation associated with autoimmune conditions.
The researchers analyzed the participants’ baseline serum vitamin D levels, vitamin D supplement use and disease activity index to the data obtained from the 12-month follow-up.
Here is what the researchers found:
- At baseline, 27.7% of patients were vitamin D deficient (< 16ng/ml).
- Over 44% of participants were supplementing with vitamin D.
- There was a mild but significant inverse relationship between vitamin D status and ESR levels (p = 0.04) at baseline.
- Baseline vitamin D levels were significantly and inversely associated with SLEDAI-2K (p = 0.01).
- There was a significant association between a rise in SLEDAI-2K levels by at least 1 point at follow up and previous vitamin D deficiency (p = 0.005).
- Those who were previously vitamin D deficient had 3.3 times the odds of an increase in SLEDAI-2K levels by greater than 10 points (p = 0.004).
- The relationship between vitamin D deficiency and SLEDAI-2k were no longer significant after adjusting for vitamin D supplementation, glucocorticoid and immunosuppressive use during the intervening time period.
The researchers concluded,
“This is the first longitudinal study of vitamin D and SLE in the Southern Hemisphere. We describe an inverse association between serum vitamin D level and SLE disease activity.”
They go on to state,
“After adjustments for covariates, namely vitamin D supplementation, glucocorticoid and immunosuppressive use during the intervening time interval, suggesting that vitamin D supplementation and treatment of SLE may modify the relationship between serum vitamin D and subsequent disease activity.”
The main strengths of the study include its prospective design and unique demographic. Also, there was no differential loss in participants at follow up, decreasing the risk of bias.
There are also some important limitations to keep in mind. Information regarding dosage of vitamin D supplementation was not present, decreasing the strength of correlation between vitamin D supplementation and decreased SLE disease activity. Furthermore, this study lacked controls to compare to the cases.
The researchers called for randomized controlled trials to determine the clinical significance of vitamin D supplementation in treating SLE.