Jan. 20, 2012

Vitamin D Indicates Lupus Disease Activity But Not Organ Damage

Vitamin D deficiency as marker for disease activity and damage in systemic lupus erythematosus: a comparison with anti-dsDNA and anti-C1q.
Mok C, Birmingham DJ, Ho LY, Hebert LA, Song H, and Rovin BH. Lupus. 2011 Oct 12. [epub ahead of print]

What is the topic?

Vitamin D exerts a wide range of influences on immune functions. Low levels of vitamin D are associated with autoimmune diseases, especially lupus. Vitamin D is activated by a chemical reaction made possible by exposure to the sun’s ultraviolet B rays. Since people with lupus may need to avoid sun exposure, this can increase the risk for vitamin D insufficiency, as can kidney failure, and treatment with steroids. Interestingly, many of vitamin D’s actions are opposite to the immunological abnormalities observed in people with lupus.

What did the researchers hope to learn?

The researchers hoped to learn about the relationship among vitamin D levels in the blood and lupus disease activity and organ damage, as well as other indicators of lupus activity such as antibodies to C1q (part of the complement system) and double-stranded DNA.

Who was studied?

209 people with lupus seen at the rheumatology outpatient clinic or hospital at the Ohio State University Medical Center between April and June 2008 were included in the study.

How was the study conducted?

Blood levels of vitamin D, as well as antibodies to C1q (anti-C1q) and double-stranded-DNA (anti-dsDNA) were measured in each lupus patient. Lupus disease activity was assessed by use of the Safety of Estrogens in Lupus Erythematosus National Assessment-SLE Disease Activity Index (SELENA-SELDAI). Organ damage was assessed by the Systemic Lupus International Collaborating Clinics Damage Index (SLICC-SDI).

Associations among levels of vitamin D and anti-C1q, anti-dsDNA, lupus disease activity, or lupus-mediated organ damage were evaluated.

What did the researchers find?

Most of the people included in the study were women who were an average age of 40 years old, and had lupus for an average of eight years. The patients had a variety of clinical features of lupus, the most prevalent of which were kidney and skin involvement. Most of the patients were taking steroids, about half were taking hydroxychloroquine, and about a third were taking azathioprine. Interestingly, over half were taking calcium supplements and about a quarter were taking vitamin D supplements. In spite of this vitamin D supplementation, about 96% of the people with lupus included in the study had vitamin D insufficiency (sub-optimal levels), while about 27% had the more serious vitamin D deficiency (much lower than normal levels).

Levels of the biologically active form of vitamin D (hereafter referred to as “vitamin D”) in the blood were negatively correlated with increased lupus disease activity (as indicated by the SLEDAI score). This pattern was also evident when relating levels of vitamin D with specific manifestations of lupus, such as disease activity involving the kidney, skin, or brain.

In addition, there was a negative correlation between levels of vitamin D and autoantibodies. These trends persisted even after adjustment for the duration of sun exposure during the month when the blood was taken from the patients.

Organ damage (as indicated by SDI score) was present in almost half of the patients, the most frequent of which included neuropsychiatric, musculoskeletal, and skin-related organ damage. In spite of this, levels of vitamin D did not correlate significantly with organ damage in the people with lupus. In addition, there were no observed correlations between levels of vitamin D and levels of complement proteins (C3 or C4).

What were the limitations of the study?

The people with lupus who participated in the study were not broken down by race/ethnicity, making it difficult to conclude about which population of women with lupus the results are most applicable to. In addition, vitamin D levels in the lupus patients were not compared to those in healthy people or to people with other immune system or rheumatic diseases. It remains unclear how levels of vitamin D in the lupus patients compare to levels seen in other people of their same age. Lastly, there are many variables that can affect vitamin D levels and the results merely demonstrate a correlation rather than a cause-effect relationship.

What do the results means for you?

The results of this study support a role for vitamin D in lupus disease activity. Specifically, this study found that most of the people with lupus included in the study had vitamin D insufficiency (sub-optimal levels), most likely due to avoidance of the sun, or perhaps to chronic use of steroids or hydroxycholoroquine, or to the low proportion of lupus patients taking vitamin D supplements.

Vitamin D levels were negatively correlated with lupus disease activity. In other words, the more vitamin D in the blood, the lower the lupus disease activity, and vice versa. Thus, levels of vitamin D in the blood may contribute to lupus disease activity, but this needs to be further investigated in larger studies.

The authors recommend that all people with lupus continue to use sunscreen and consult with their physician about adequate intake of vitamin D.

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