Low vitamin D levels found in NMOSD patients, per study review

Meta-analysis covers data on more than 900 people in Asia

Margarida Maia, PhD avatar

by Margarida Maia, PhD |

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People with neuromyelitis optica spectrum disorder (NMOSD) have significantly lower vitamin D levels in their blood than do healthy individuals, according to a meta-analysis of data from studies covering more than 900 people in Asia.

While the findings don’t prove that vitamin D deficiency causes NMOSD, they call attention to the importance of regular monitoring vitamin D levels in the blood and prescribing supplementation when those levels are lower than normal.

The meta-analysis study, “Vitamin D status and neuromyelitis optica spectrum disease: A systematic review and meta-analysis,” was published in Clinical Neurology and Neurosurgery.

Vitamin D, found in certain foods and made by the skin when exposed to sunlight, is best known for its role in bone health. But there’s growing evidence that vitamin D plays additional roles, and may help in taming inflammation and keeping the immune response in check.

Increasing research also suggests that people with lower levels of vitamin D are more likely to develop autoimmune diseases, such as multiple sclerosis (MS). Like MS, NMOSD is marked by abnormal immune attacks on healthy cells of the central nervous system (brain and spinal cord).

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Contradictory research on low vitamin D levels

Previous studies on a potential link between vitamin D and NMOSD have yielded contradictory results. Some reports showed lower vitamin D levels or higher rates of vitamin D deficiency in people with NMOSD, while others found no such differences.

To shed light on the matter, a team of researchers in China systematically analyzed published studies up to November 2022 describing blood vitamin D levels in NMOSD patients compared with healthy people.

A total of six studies, involving 319 people with NMOSD and 595 healthy controls, were included in the meta-analysis. All were conducted in Asia: four in China, one in Korea, and one in Thailand. The mean ages for both groups ranged from 36 to 45.

Results showed that compared with healthy controls, people with NMOSD had significantly lower blood levels of vitamin D.

Those levels were consistently lower in NMOSD patients regardless of their mean age (studies involving people younger than 40 vs. those covering people 40 and older), the proportion of women (groups that covered up to 88% women vs. those in which the percentage of women was below 88%), and the year each study was published (studies published before 2015 vs. later studies).

Three studies measured 25(OH)D, the major circulating form of vitamin D, while the other three measured 25(OH)D3, a form of vitamin D that is made by the skin or absorbed from animal foods. People with NMOSD had significantly lower levels of the vitamin regardless of which of its forms was measured.

However, studies involving fewer than 100 people and those of moderate quality — assessed based on their design and content — showed no significant differences in vitamin D levels between NMOSD patients and healthy controls.

In two studies, people with NMOSD were on oral prednisolone and/or azathioprine, two immunosuppressants commonly used to manage the disease. In these two studies, but not in those in which patients were not on immunosuppressants or the use of medications wasn’t mentioned, vitamin D levels were significantly lower in the NMOSD group.

“Therefore, there was still unexplained [variability] between groups,” the researchers wrote, adding that “race, country, age, gender, different latitudes in which participants live, blood sampling season, different [height-weight ratio], medications that affect vitamin D levels, vitamin D testing indicators, vitamin D measurement methods and more” may have contributed to this variability.

The researchers said that to their knowledge, the study “is the first meta-analysis demonstrating the association between NMOSD and vitamin D levels.”

“Modern lifestyles,” associated with more time spent in buildings and less sun exposure, “even in sunny countries,” and “avoiding sun exposure, using sunscreen, taking sun protection measures or even foundation may be some of the reasons for low [blood] vitamin D in patients with NMOSD,” the researchers wrote. “Further prospective studies are needed to clarify whether reduced vitamin D level is a causal factor in the [development] of NMOSD or a consequence of this,” they concluded, urging doctors to monitor and supplement vitamin D as needed.