Sun Exposure May Reduce MS Risk

Multiple Sclerosis Linked to Lack of UV Radiation, Vitamin D

From the WebMD Archives

Aug. 7, 2003 -- A new study shows that lots of sun exposure -- particularly when you're young -- may lower your risk for multiple sclerosis.

No one is recommending that you let your kids bake in the sun for hours on end. But previous studies have shown that multiple sclerosis is more common in areas of the world with less sun exposure -- areas further from the equator. So in the furious search for a multiple sclerosis cause, researchers looked at the lack of sunlight as one possibility.

Multiple sclerosis (MS) is a disease of the nerves that can cause a variety of problems, such as lack of muscle control and strength, blurry vision, trouble with balance, and numbness.

Researchers compared 136 people under age 60 with multiple sclerosis to nearly 300 people without it. The volunteers were all natives of Tasmania, an area that gets little sunlight in the winter and has a high prevalence of multiple sclerosis. The new study appears in the August issue of the British Medical Journal.

Researchers asked volunteers questions about their sun exposure, including how they protect themselves against the sun. They were also asked about their use of vitamin D supplements between ages 10 and 15 since previous studies have suggested that vitamin D may help protect against multiple sclerosis. In addition, vitamin D is produced in the body when the skin is exposed to the sun.

Higher sun exposure from ages 6 to 15 -- an average of two or three hours or more a day in the summer during weekends and holidays -- was associated with a 70% drop in multiple sclerosis risk.

Fairer-Skinned People at Higher Risk

Researchers also looked at skin damage and skin color. It turned out that fairer-skinned people were at a greater risk of developing multiple sclerosis earlier in life.

People with higher sun exposure between ages 6 and 15 and those with greater skin damage from the sun had a decreased risk.

The season of the year also played a role. Higher exposure in the winter seemed to decrease risk more than higher exposure in the summer. This may explain why the number of multiple sclerosis cases in Tasmania is high.

Researchers say the findings suggest there may be a link between multiple sclerosis and insufficient ultraviolet radiation or vitamin D -- or both.

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SOURCES: British Medical Journal, August 2003. News Release, British Medical Journal. WebMD Medical Reference provided in collaboration with The Cleveland Clinic: What Causes MS?
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