New research suggests that having higher circulating levels of vitamin D is associated with a reduced risk for multiple sclerosis, although this relationship was not seen for black and Hispanic individuals, according to a study in the December 20 issue of JAMA.
Multiple sclerosis (MS) is among the most common neurological diseases in young adults, affecting 350,000 individuals in the United States and 2 million worldwide, according to background information in the article. Previous research has indicated that vitamin D may provide a protective effect, but evidence has been inconclusive.
Kassandra L. Munger, M.Sc., of the Harvard School of Public Health, Boston, and colleagues examined whether high blood levels of 25-hydroxyvitamin D is linked with a lower risk of MS. The study included more than 7 million U.S. military personnel who have serum samples stored in the Department of Defense Serum Repository. Multiple sclerosis cases were identified through Army and Navy physical disability databases and diagnoses were confirmed by medical record review. Each case (n = 257) was matched to two controls by age, sex, race/ethnicity, and dates of blood collection.
The researchers found that among whites, there was a 41 percent decrease in MS risk for every 50-nmol/L (nanomoles per liter) increase in 25-hydroxyvitamin D. In analysis by quintiles, MS risk was highest among individuals in the bottom quintile and lowest among those in the top quintile of 25-hydroxyvitamin D levels. Those in the top quintile had a 62 percent lower risk of MS compared to those in the bottom quintile. The inverse relation with multiple sclerosis risk was particularly strong for 25-hydroxyvitamin D levels measured before age 20 years. Among blacks and Hispanics, who had lower 25-hydroxyvitamin D levels than whites, no significant associations between vitamin D and multiple sclerosis risk were found.
"Although this association was not seen among blacks, their smaller sample size and substantially lower 25-hydroxyvitamin D levels may have reduced the power to detect an association in this group," the authors write.
"A broad recommendation for a several fold increase in vitamin D intake among adolescents and young adults requires stronger evidence than that provided by observational studies alone. First-degree relatives of individuals with MS are at a higher risk of developing MS, and a prevention trial among this population would be possible and timely. Meanwhile, use of vitamin D supplements for MS prevention should not be undertaken until efficacy is proven," the researchers conclude.
(JAMA. 2006;296:2832-2838. Available pre-embargo to the media at www.jamamedia.org)
Editor's Note: This work was supported by grants from the National Institute of Neurological Diseases and Stroke and by a pilot grant from the National Multiple Sclerosis Society. Co-author Dr. Bruce Hollis is a consultant for Diasorin. No other disclosures were reported. Please see the article for additional information, including other authors, author contributions and affiliations, financial disclosures, funding and support, etc.
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