Can sunshine help prevent MS in children?

While too much sun exposure can damage skin cells and increase the risk of skin cancer, sunlight can have health benefits as well. A study published online December 8 by Neurology, the journal of the American Academy of Neurology, showed that for children and young adults, spending more time outside reduced their odds of developing multiple sclerosis (MS).

Low sun exposure, low ultraviolet radiation (UVR) exposure, and low vitamin D levels already have been well-established as environmental risk factors for adult-onset MS. Signs of the disease typically appear when a person is between age 20 and 50. But 3 to 5 percent of some one million MS patients in the United States began experiencing symptoms before age 16, according to the National Multiple Sclerosis Society. For children with the disease, symptoms are highly inflammatory, with more frequent relapses than adults experience.

For this investigation, scientists at the University of California in San Francisco (UCSF) and the Australian National University wanted to see if the connection between sun exposure and MS held true among this smaller population of young people diagnosed with MS.

The researchers compared data from 332 participants ranging in age from 3 to 22, who had had MS for an average of seven months, and included data from 534 young participants without MS. Children with MS were matched to the controls on the basis of age and sex.

In questionnaires completed by subjects with MS or their parents, about one in five indicated that they spent less than 30 minutes daily outdoors during the previous summer. On the other hand, only about 6 percent of those without MS said they spent less than 30 minutes outdoors a day.

After adjusting for other MS risks, the study authors calculated that those who spent an average of 30 minutes to one hour outdoors daily had a 52 percent lower chance of developing MS than those who spent an average of less than 30 minutes outdoors daily.

“Sun exposure is known to boost vitamin D levels,” said the co-senior author, Emmanuelle Waubant, MD, PhD, a professor in the department of neurology at UCSF in a statement. “It also stimulates immune cells in the skin that have a protective role in diseases such as MS. Vitamin D may also change the biological function of the immune cells and, as such, play a role in protecting against autoimmune diseases.”

Dr. Waubant and her collaborators also highlighted how geography can make a difference. They estimated that residents of Florida (where sunlight is more intense) would be 21 percent less likely to have MS than residents of New York.