ORLANDO, Fla. (Ivanhoe Newswire) -- Spending time in the sun may help prevent multiple sclerosis (MS), according to the results of a recent twin study.

Because they share the same genes, experts say identical twins stand an equal chance of contracting certain diseases like multiple sclerosis. But what happens when one twin contracts MS and the other does not? This question drove researchers at the University of Southern California in Los Angeles to study 79 pairs of twins who were predisposed to MS. In each pair, only one of the twins successfully contracted MS, leading researchers to believe there may be environmental differences between the two. After analyzing data that showed how much sun exposure each twin got as a child, researchers found twins who spent a great deal of time indoors were more likely to get MS than twins who spent a great deal of time outdoors. In fact, a twin who spent time tanning in the sun as a child was 49 percent less likely to get MS than his or her identical sibling.

"Sun exposure appears to have a protective effect against MS," Talat Islam, MBBS, PhD, and Thomas Mack, MD, MPH, of the Keck School of Medicine of the University of Southern California, are quoted as saying. "Exposure to ultra violet rays may induce protection against MS by alternative mechanisms, either by directly altering the cellular immune response or indirectly by producing immunoactive vitamin D."

Douglas Feinstein, Ph.D., a neuroscientist at the University of Illinois in Chicago, told Ivanhoe some scientists believe MS is partially caused by early exposure to an unknown virus. Because the disease is largely hereditary, he said there are no real preventive patients can take. "If you know one of your family members has it, there's nothing you would do to reduce your chances [of getting MS]," he said.

SOURCE: Ivanhoe interview with Douglas Feinstein, Ph.D., Neurology, published online July 24, 2007