Growing up in a place where there’s lot of sun may guard you from multiple sclerosis decades later.
So say Canadian researchers, who theorize that the protective factor is from exposure to UV-B rays that help the body to produce vitamin D.
The new findings from the University of British Columbia in Vancouver support previous studies that have linked low levels of the sunshine vitamin with an increased risk of MS — an unpredictable, often disabling disease of the central nervous system.
“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,” said epidemiology professor Helen Tremlett, lead author of the study in the journal Neurology.
Tremlett’s team tracked the histories of 151 women with MS who were diagnosed around age 40, and 235 women of similar age without MS. The women lived across the United States and nearly all were white.
Subjects completed questionnaires about their sun exposure in summer, winter and across their lifetime, including youth and teenage years. High sun exposure during summer was defined as more than 10 hours per week, and more than four hours per week in the winter.
Results showed that women who lived in sunnier regions and had the highest exposure to UV-B rays were 45% less likely to develop MS than those who lived in regions with the lowest UV-B exposure.
Childhood sun exposure also played a significant role. Women who lived in the sunniest regions between ages of 5 and 15 were 51% less apt to develop MS than who lived in the least sunny areas during the same age span.
“Our research showed that those who did develop MS also had reduced sun or outdoor exposure later in life, in both summer and winter, which may have health consequences,” Tremlett noted.
A limitation of the study is that 98% of the participants were white. More research is needed to see if a more diverse study yields the same results. Moreover, UV-B rays are also linked to skin cancer.