Higher vitamin D levels are associated with slightly less disability and greater preservation of gray matter in patients with multiple sclerosis, according to a 5-year observational study.

The researchers assessed 25-hydroxyvitamin D levels, clinical disability, and MRI brain volumes annually in 469 patients with relapsing-remitting multiple sclerosis (MS) or clinically isolated syndrome, all members of a longitudinal MS cohort study at the University of California, San Francisco.

Dr. Ellen Mowry
They found that for every 10-ng/mL increase in 25-hydroxyvitamin D levels, subsequent EDSS (Expanded Disability Status Scale) scores were 0.05 points lower (95% confidence interval –0.091 to –0.003; P = .037), and subsequent normalized gray matter volume was 7 cc higher (95% CI 2.4, 11.5; P = .003). The results were adjusted for age, sex, ethnicity, smoking status, body mass index, and use of MS treatments.

Based on the results and a growing body of literature suggesting a role for vitamin D in MS, lead investigator Dr. Ellen Mowry, an assistant professor of neuroimmunology at Johns Hopkins University, Baltimore, often supplements her patients to a vitamin D level of 40-60 ng/mL, which usually takes 2,000-4,000 international units a day.

“The preponderance of the observational evidence is in favor of supplementing, and I think those levels are the most strongly supported by the data. Above 60 ng/mL, there are very few data to say whether or not the effect remains the same,” she said at the annual meeting of the American Academy of Neurology.

Dr. Mowry said she is careful to tell her MS patients that although observational studies suggest vitamin D is safe and helpful, ongoing randomized trials may prove otherwise.

The average age of patients in her study was 42 years; their median disease duration was 5 years, and about two-thirds were women. Their baseline vitamin D levels were low at around 28 ng/mL.

Mean EDSS scores were about 1.5 at the start of the study, and about 2 at its end. Mean normalized gray matter volumes were 985 cc at baseline and 964 cc at the end of 4 years. Only 9% of the subjects took vitamin D supplements at the start of the study, but almost half (43%) took them at its end.

Trends were favorable for an association between vitamin D levels and preservation of brain parenchymal volume, but the results were not statistically significant.

The results are in line with a 2006 study that found an inverse association between vitamin D levels and the risk for developing MS (JAMA 2006;296:2832-8).

Previously, Dr. Mowry and other researchers have demonstrated that vitamin D levels are inversely associated with MS relapse risk in both children and adults (Ann. Neurol. 2010;67:618-24; Ann. Neurol. 2010;68:193-203).

Dr. Mowry is the principal investigator in a randomized treatment trial that will assess the impact of high- and low-dose vitamin D supplementation on attack rates, numbers of new lesions, and changes in brain volume in relapsing-remitting MS.

The study was funded by a grant from the National Institutes of Health and by GlaxoSmithKline and Biogen Idec. Dr. Mowry reported receiving research support from Teva Pharmaceuticals.