Multiple sclerosis (MS) is among the most common neurological diseases in young adults, affecting 350,000 individuals in the United States and two 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 seven 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.

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.

According to the article, fatigue is the most frequent symptom of multiple sclerosis (MS) and is often difficult to treat. Fatigue is experienced by 76 percent to 92 percent of MS patients and is often profoundly debilitating, the article states.

Hrayr P. Attarian, M.D., of the University of Vermont, Burlington, and colleagues investigated whether circadian rhythm abnormalities or sleep disturbances exist in patients with MS and if they correlate with fatigue and daytime sleepiness. Circadian rhythms are the cycles of sleep and wakefulness, controlled by part of the brain.

The researchers studied 15 patients with MS and fatigue compared with 15 patients with MS without fatigue and 15 healthy people without MS.

The researchers found that of the 15 patients with MS, two had delayed sleep phase, ten had disrupted sleep, and three had normal sleep. One of the 15 non-fatigued MS patients had irregular sleep cycles, two others had disrupted sleep and 12 had normal sleep. All 15 participants without MS had normal sleep. Nine patients with MS and fatigue scored high on a sleep scale test, indicating excessive daytime sleepiness. Only two patients with MS without fatigue scored high on this test. None of the participants without MS were fatigued.

The researchers found a relationship between fatigue and abnormal sleep cycles or disrupted sleep, and between excessive daytime sleepiness and fatigue in MS patients.