Although multiple sclerosis onset usually occurs between 20 and 50 years old, 3-5% of individuals may experience onset before reaching 18. Low sun exposure, low ultraviolet radiation (UVR) exposure, or low vitamin D status have been linked to a higher risk of developing MS in both adults and children.
In the current study, researchers investigated the associations between sun exposure at various periods of life and relapse risk in pediatric-inset MS. To do so, they recruited 334 patients aged between 4 and 21 years old who had MS onset prior to 18 years old. Time spent in the sun at various periods of life was assessed via an environmental questionnaire completed by participants' parents or guardians, while ambient UVR exposure was determined using zip codes.
Relapses were defined as new or returning symptoms lasting at least 24 hours following a remission of at least 30 days from the previous MS attack without a fever or infection. Altogether, 62% of the participants experienced at least one relapse from disease onset until the follow-up period's end.
The researchers found that 30 minutes or more of daily sun exposure during the first summer of life was linked to a 33% lower risk of relapse compared to less than 30 minutes of exposure.
They further found that 30 minutes or more of daily sun exposure in the second trimester of pregnancy was also linked to a 32% reduced relapse risk. UVR doses and time spent in the sun later in life were not significantly linked to relapse risk.
"Our findings suggest that sun exposure in early childhood may have long-lasting benefits on the progression of childhood-onset MS. Future studies should look at how time in the sun at other time periods before and after MS diagnosis affects disease course, to better guide sun exposure recommendations for children with MS and to help design potential clinical trials," said study author Gina Chang, MD, MPH, of The Children's Hospital of Philadelphia and member of the American Academy of Neurology, in a press release.
Sources: Science Daily, Neurology Neuroimmunology and Neuroinflammation
