Low Vitamin D Levels May Increase Risk of Developing MS
Abstract & Commentary
By Brian R. Apatoff, MD, PhD, Associate Professor of Neurology and Neuroscience; Director, Multiple Sclerosis Clinical Care and Research Center. Dr. Apatoff reports no financial relationship relevant to this field of study.
Synopsis: Vitamin D supplementation may lower the risk of developing multiple sclerosis.
Source: Munger KL, et al. Serum 25-Hydroxyvitamin D Levels and Risk of Multiple Sclerosis. JAMA. 2006; 296:2832-2838.
The investigators performed a prospective, case-control study of more than 7 million U.S. military personnel who had serum samples stored in the Department of Defense Serum Repository. Multiple sclerosis (MS) cases were identified through military disability databases from 1992 to 2004, and the diagnosis of definite or probable MS was confirmed by independent review of the medical records. Each established case of MS (n = 257) was matched to 2 control cases by age, sex, race/ethnicity, and dates of blood testing. Vitamin D status was determined by averaging 25-hydroxyvitamin D levels in 2 or more serum samples collected prior to the onset of initial MS symptoms.
Among the white military personnel diagnosed with MS (n = 148; 296 controls), the risk of developing MS was significantly decreased with increasing levels of 25-hydroxyvitamin D. Among whites, there was a 41% decrease in MS risk for every 50 nmol/L increase in 25-hydroxyvitamin D (odds ratio 0.59; 95% confidence interval 0.36-0.97; P = 0.04). There was no significant difference between male and female groups. In analysis by quintiles, MS risk was highest in the individuals in the bottom quintile, and risk for MS was lowest among those in the top quintile of 25-hydroxyvitamin D levels. The overall association between MS risk and 25-hydroxyvitamin D levels was not statistically significant among blacks and Hispanics, but none of the black patients or their controls had high levels of vitamin D.
Commentary
The incidence of MS worldwide is higher in northern latitudes and lower in the equatorial regions. In addition to recognized genetic and environmental/infectious factors, one protective variable of southern climates might be increased vitamin D production from sunlight exposure. Previous epidemiological analyses of large nursing databases from the Harvard School of Public Health have demonstrated that women whose vitamin D intake was approximately 400 IU/day had a 40% lower risk of developing MS than women who did not take supplements (Neurology Alert. 2004).
Vitamin D is also commonly added to multivitamins and combined with calcium, usually for postmenopausal women at increased risk for osteoporosis. While the current study does suggest a preventative role for vitamin D in reducing the risk of acquiring MS, it does not address whether vitamin D supplements can alter the course of existing MS. Since first degree family members of persons with MS have approximately a 20-fold increased risk of developing MS, is it reasonable for this "at-risk" group to be take vitamin D supplements?
In general, MS patients may have reduced sun and UV light exposure because of avoidance of heat. They may also be at higher risk of osteopenia from treatment with corticosteroids and a more sedentary lifestyle. It is reasonable to have patients on a vitamin D supplement for this health benefit alone. More study is needed of the immune mechanisms of MS and the immunomodulatory effects of vitamin D, before we can make broader recommendations regarding vitamin D supplementation.
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