To do so, they tracked the histories of about 150 women diagnosed with multiple sclerosis around age 40 and about 230 women around age 40 without multiple sclerosis. They then asked the participants to complete a questionnaire that asked about their sunlight exposure during the summer and winter from adolescence to adulthood.
After analyzing the results, they found that women who lived in sunnier climates with the highest exposure to UV-B rays were 45 percent less likely to develop multiple sclerosis.
The number was even higher for those exposed to sunlight as children. Women who spent lots of time in the sun between ages 5 and 15 were 51 percent less likely to get multiple sclerosis, compared to those who lived in shadier areas during the same time span.
“Our findings suggest that a higher exposure to the sun’s UV-B rays, higher summer outdoor exposure and lower risk of MS can occur not just in childhood, but into early adulthood as well,” co-author Helen Tremlett said in a statement.
“While previous studies have shown that more sun exposure may contribute to a lower risk of MS, our study went further, looking at exposure over a person’s life span. We found that where a person lives and the ages at which they are exposed to the sun’s UV-B rays may play important roles in reducing the risk of MS,” Tremlett said. “The methods we applied to measure sun exposure could also be used in future studies.”