Does Sun Exposure in Early Years Delay MS Onset?

Exposure to sunlight may delay the development of multiple sclerosis (MS), according to a new study from researchers in Denmark. The work, titled “Association between age at onset of multiple sclerosis and vitamin D level–related factors,” appeared October 7, 2015 in the journal Neurology. The report also indicated that being overweight at age 20 may hasten the onset of the degenerative neurological condition.

MS develops due to an autoimmune attack on the body’s own myelin, a fatty substance that surrounds nerve cells and helps them to communicate. This immune system’s self-attack occurs for reasons that are not currently understood. When myelin is damaged, symptoms of MS can result, including loss of movement, pain, loss of vision and sensory problems. Lifestyle choices that impact the immune system may potentially affect when a person develops MS.

In the current study, led by Julie Hejgaard Laursen, MD, PhD, of Copenhagen University Hospital in Denmark, researchers included 1,161 people with MS. The study participants filled out questionnaires and donated blood samples. The scientists established two groups of individuals, based on whether or not they reported spending time in the sun every day or not, and also collected information on the use of vitamin D supplements and the consumption of fatty fish. Overall, 88 percent of the study participants spent time in the sun each day.

People who spent sun time each day had an average 1.9 year delay in the onset of MS compared to the group who did not spend time in the sun. The average age of MS onset for the sun-group was 32.9 years, versus 31 for the group that did not spend time in the sun each day. The scientists did not find any association between using vitamin D or other supplements and the delay of MS onset. However, naturally produced vitamin D could still play a role.

“It appears that both UVB rays from sunlight and vitamin D could be associated with a delayed onset of MS,” Laursen noted. “However, it’s possible that other outdoor factors play a role, and these still have to be identified.”

Being overweight also had an impact on the onset of MS. A total of eighteen percent of study subjects were overweight. People who were overweight at age 20 developed MS 1.6 years earlier than people who were of average weight and 3.1 years earlier when compared to people who were underweight at 20.

“A limitation of the study is the risk of recall bias because participants were asked to remember their sun, eating and supplement habits from years before,” Laursen said. “In particular, someone with a long history of MS and onset of the disease at an early age, may wrongly recall a poor sun exposure. Additionally, only Danish patients were included into the study, so there should be caution when extending the results to different ethnic groups living in different geographic locations.”