Summary Aim: This study aims to determine the contributions of sun exposure and ultraviolet radiation (UVR) exposure to the risk of pediatric-onset multiple sclerosis (MS). Methods: Children with MS and controls recruited at multiple centers in the US were matched for sex and age. Multivariable conditional logistic regression was used to investigate the association of time spent outdoors daily in summer, sun protection use, and summer ambient UVR dose in the year before birth and the year before diagnosis, with the risk of MS, adjusting for sex and age, race, season of birth, child’s skin color, mother’s education, exposure to tobacco smoke, overweight, and Epstein-Barr virus infection. Results: 332 children with MS (median disease duration: 7.3 months) and 534 controls were included after comparison by sex and age. In a fully adjusted model, compared with spending <30 minutes outdoors per day during the most recent summer, increased time outdoors was associated with a marked reduction in the odds of developing MS, with evidence of dose response (30 minutes to 1 hour: adjusted odds ratio (AOR) = 0.48, 95% confidence interval [95% CI] 0.23-0.99, p = 0.05; 1-2 hours: AOR = 0.19, 95% CI 0.09-0.40, p < 0.001). The highest dose of summer ambient UVR was also protective for MS (AOR = 0.76 per kJ/m2, 95% CI: 0.62-0.94, p = 0.01). Conclusions: If this is a causal association, spending more time in the sun during the summer may be highly protective against the development of pediatric MS, in addition to residing in a sunnier location. |
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A new study suggests that children, teenagers and young adults who spend more time outdoors during the summer months and live in areas of the country that expose them to higher amounts of ultraviolet light have a lower risk of developing multiple sclerosis (MS). in childhood.
Although rare, MS can develop in children, although most people begin to have symptoms of the disease between the ages of 20 and 50. The research appears in Neurology , the medical journal of the American Academy of Neurology.
The study also found that those who had more sun exposure during their first year of life were also less likely to develop MS.
“Providing guidance on the best amounts of sunlight exposure and weighing the benefits against the risks is challenging,” said study author Emmanuelle Waubant, MD, PhD, of the University of California, San Francisco and a member of the American Academy of Neurology. "We found that spending one to two hours outdoors per day provided the greatest benefit, but spending as little as 30 minutes outdoors per day can reduce the risk of MS by approximately half."
The study involved 332 people with MS who had the disease for an average of seven months. They were matched with 534 people of similar age and sex who did not have MS. The participants ranged in age from three to 22 years old.
Sun exposure was measured as time spent outdoors, use of sun protection such as a hat, clothing, and sunscreen, plus the amount of UV light exposure based on where participants lived at birth and at time. of the study. Children or their parents or guardians answered a questionnaire about how much time they spent outdoors each day at different ages and over the past year.
In the summer before the study, 19% of participants with MS said they spent less than 30 minutes outdoors, compared to 6% of those without MS. And 18% of participants with MS spent one to two hours outdoors, compared to 25% of those without MS.
After adjusting for smoke exposure, sex and other factors that could affect MS risk, the researchers found that people who spent an average of 30 minutes to an hour outdoors during the summer before the study had a 52% less likely to develop MS compared to those who spent an average of less than 30 minutes outdoors a day.
Those who averaged even more time outdoors each day, between one and two hours, were 81% less likely to get MS than those who spent an average of less than 30 minutes outdoors per day.
"It’s important to note that excessive unprotected sun exposure also has risks, and our study found that spending two hours or more outdoors every day did not further reduce the risk of MS compared to one to two hours," Waubant said.
Spending more time outdoors during the first year of life was associated with lower odds of MS. The researchers found that location mattered, too. Brighter sunlight where a participant lives was associated with lower odds of MS. For example, researchers estimate that someone who lives in Florida is 21% less likely to have MS compared to someone who lives in New York.
The study does not prove that sun exposure prevents MS, but it does show an association.
One limitation of the study is that children and their parents or guardians had to remember sun exposure and sun protection use from years before, and that memory may not be accurate.
The study was supported by the National Institutes of Health and the National MS Society.
