Sun exposure reduces risk for pediatric-onset MS

Spending more time in sunlight was associated with a significantly reduced risk for pediatric-onset MS, according to findings presented at the ACTRIMS virtual meeting.

The relationship between sun exposure and MS has already been characterized in adults. Not only has a lack of sun exposure been established as an MS risk factor, but data recently published in PNAS USA provided evidence that time spent in the sun reduces the severity of the disease in adults as well.

“MS etiology is complex and probably involves multiple risk factors,” Prince Sebastian, a third-year medical student at the Australian National University, said during a presentation. “In particular, low sun exposure, low ultraviolet radiation — or UVR — exposure and low vitamin D have all been well-established as modifiable environmental risk factors for the disease.”

However, Sebastian said the involvement of sunlight in pediatric-onset MS is unclear.

In their analysis, Sebastian and colleagues matched 322 children with MS in the U.S. and 534 controls based on sex and age. After adjusting for covariates like race, overweight and infection with Epstein-Barr virus — among several other factors — the researchers found that spending 30 minutes to 1 hour in the sunlight each day during the summer was associated with a 2.6-fold reduced risk for MS (OR = 0.39; 95% CI, 0.17-0.86), compared with spending less than 30 minutes outside. Spending 1 to 2 hours in the sun each day — as opposed to only 30 minutes — was associated with a 7.4-fold reduced risk for MS (OR = 0.13; 95% CI, 0.06-0.31).

Additionally, higher summer ambient UVR levels were protective against MS in children (OR = 0.8 per kJ/m²; 95% CI, 0.64-1). Based on their findings, the researchers estimated that a child living in Florida would have a 20% reduced likelihood of developing MS compared with a child living in New York (OR = 0.83; 95% CI, 0.69-1).

However, the researchers found that the use of sun protection was not associated with MS risk (OR = 0.95; 95% CI, 0.88-1.03), contrary to their hypothesis that its use would limit sun exposure.

“That’s probably because people who tend use sun protection also tend to get more sun exposure anyway,” Sebastian said.

Another surprising finding was that greater serum 25-hydroxyvitamin D levels were associated with greater risk for MS (OR = 1.07; 95 CI, 1.05-1.09).

“We think this is because children with MS have been taking vitamin D supplementation following their diagnosis,” he said. “Unfortunately, we didn’t have complete data on vitamin D supplementation, so we couldn’t investigate this further.”

Nonetheless, Sebastian said the findings support the concept of using regular sun exposure as an intervention to prevent the development or progression of pediatric-onset MS.

Ostkamp P, et al. Proc Natl Acad Sci U S A. 2021;doi:10.1073/pnas.2018457118.

Sebastian P, et al. Abstract S1.3. ACTRIMS Forum; Feb. 25-27, 2020 (virtual meeting).