No connection found between vitamin D levels and MS severity
African Americans with MS have significantly lower levels of vitamin D than African Americans who do not have MS, says a new study, but these levels are not linked to disease severity. The authors conclude that larger studies of diverse populations are necessary to fully understand the relationship of MS and vitamin D. Jeffrey Gelfand, MD, Ari Green, MD, and colleagues (University of California, San Francisco) report their findings in Neurology (2011;76:1824–1830). The study was funded by a National MS Society/American Academy of Neurologist Clinician Scientist Award to Dr. Green, and a research grant funding genetic studies in ethnically distinct populations to Jorge Oksenberg, PhD.
Background: A number of genetic and environmental factors influence whether a person will get MS. These factors may also impact the severity of the disease. Research is increasingly pointing to a reduced level of vitamin D in the blood as a risk factor for developing MS. In lab mice, vitamin D can reduce the effects of EAE, an MS-like disease. The National MS Society is funding several projects in this area, including a new clinical trial getting underway to test whether vitamin D can reduce disease activity in people who have MS.
African Americans are at increased risk for having low vitamin D levels, possibly because melanin, which determines the level of pigment in the skin, acts as a filter of ultraviolet (UV) light, limiting the amount of vitamin D that can be produced by the body in response to sunlight. Generally, the risk of MS in African Americans is around half that of Caucasian Americans. This team previously reported that African Americans tended to have a more aggressive course of disease than Caucasian Americans, were at higher risk for developing mobility impairments, were more likely to develop MS later in life, and were at higher risk for having symptoms restricted to the optic nerve and spinal cord (Neurology 2004;63:2039-45). For this study they examined vitamin D levels in African Americans with MS to determine any connection between these levels and disease severity in this population.
The Study: The team studied 339 African Americans with MS and 342 African American controls without MS, recruited through the African American MS Genetics Project led by Drs. Oksenberg and Dr. Bruce Cree MD, PhD. Detailed clinical and genetic information was available for the participants, as well as blood samples. Researchers looked at vitamin D levels in the blood, the severity of the disease, the amount of ultraviolet exposure for participants based on where they lived, and the proportion who had European genetic ancestry.
Of the group with MS, 77% were deficient in vitamin D, compared to 71% of those without MS. There was no association between vitamin D levels and disease severity. People with MS were exposed to less UV radiation than those without MS and lived about one degree of latitude farther north. People with a higher proportion of European genetic ancestry were less likely to have low vitamin D levels than people with a lower proportion of European ancestry. The link between low vitamin D levels and MS was weaker, but still existed after adjusting for these differences.
This study adds accumulating data of a link between MS risk and lower levels of vitamin D. The authors conclude that larger studies of diverse populations are necessary to fully understand the relationship of MS and vitamin D.
Read more about vitamin D research funded by the National MS Society.
Read more about the National MS Society’s African American Advisory Council and resources for African Americans with MS.