Sun exposure reduces risk of multiple sclerosis: Study

Sun exposure reduces risk of multiple sclerosis: Study

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By Dr. Ananya Mandal, MDFeb 8 2011

A new Australian study has found that increased sun exposure and higher vitamin D levels may help to protect against the risk of developing multiple sclerosis (MS).

MS is a severely debilitating autoimmune disease whose symptoms include loss of balance, slurred speech, muscle spasms, and difficulty walking or moving the legs or arms. This study shows that MS occurs more among people who live in less sunny regions farther from the equator.

According to research co-author Anne-Louise Ponsonby, a professor, epidemiologist and public health physician with the Murdoch Children’s Research Institute at Royal Children’s Hospital in Melbourne, the exact mechanism by which sun exposure and vitamin D may help protect against a “multi-factorial disease” like MS is not yet clear. However vitamin D is an important agent that helps modify immune system functioning. She explained that “laboratory studies have shown higher vitamin D levels can dampen down some of the adverse immune overactivity that occurs in autoimmune diseases such as MS.” Associate Professor Robyn Lucas from the ANU college of medicine who led the study said, “The risk of having a first event (symptoms of MS) was lower in people with more sun exposure.”

The study was conducted with the support of the National Multiple Sclerosis Society of the United States of America, the National Health and Medical Research Council of Australia, the ANZ William Buckland Foundation, and Multiple Sclerosis Research Australia. The observations are published in the Feb. 8 issue of the journal Neurology.

Authors write that although past research has uncovered a similar association between sun exposure and MS risk protection, this is the first study to examine the impact of sun exposure among individuals who are just experiencing precursor signs of MS, but have not yet actually been diagnosed as having the disease. They involved 216 patients between the ages of 18 and 59 who had early pre-diagnosis signs of MS between 2003 and 2006. The patients were located in one of four different locations in Australia, with latitudes ranging from 27 degrees South to 43 degrees South. They also compared these results with nearly 400 other study participants without any disease indications.

The participants were asked to report how much time they had spent in the sun over weekends and holidays during both summer and wintertime over the course of four different time-frames: between the ages of 6 and 10; 11 and 15; 16 and 20; and during the three years leading up to the study. In addition, skin exams were conducted, and blood samples taken to measure vitamin D levels.

Results showed that higher the amount of both past and recent sun exposure meant lower risk for developing early signs of MS. Specifically noting that sun exposure ranged from 500 to 6,000 kilojoules per meter squared, the authors found that for every additional 1,000 kilojoules of exposure, the risk of developing the first signs of MS dropped by 30 percent. In addition, having a higher vitamin D level was also independently linked to a lower risk for developing MS. Also as expected those living in the study regions furthest away from the equator faced a 32 percent greater risk for signs of MS than study participants who lived closest to the equator. The results also revealed that those with the most signs of skin damage faced a 60 percent lower risk for developing initial indications of MS compared with those with the least amount of skin damage caused by the sun.

Ponsonby however added a word of caution regarding “excessive exposure” to sun that can give rise to a number of adverse health consequences, including possible skin cancer. Dr. Moses Rodriguez, a professor of neurology and immunology at the Mayo Clinic in Rochester, Minn., said, “it’s all about not overdoing it”. “Dermatologists can get up in arms with these sorts of studies because they’re saying that the amount of sun exposure that you would need to get protection against something like MS would be the amount that would increase your risk for melanoma and skin cancer dramatically,” Rodriguez said. He added, “But in truth, it appears that your mother’s idea to go out and play in the sun was not necessarily a bad idea…It’s just that everything has to be tempered. You don’t, for example, want someone to go take 10,000 units of vitamin D. Yes, you need some sun exposure, and you need some vitamin D. Both appear to have some protective effect in terms of MS. But neither is the whole answer, and neither is going to cure MS.”

According to Nicholas G. LaRocca, vice president of health care delivery and policy research at the National Multiple Sclerosis Society in New York City, “I do think this is a very important study… It really moves this field forward in terms of refining our understanding of what puts people at risk for developing MS, and what might reduce this risk.” However he cautioned, “Reading this [study], one might be tempted to say ‘well, I should move to a sunnier climate’ or ‘I should dose myself with tons and tons of vitamin D,’…But I don’t think we know enough to really understand what the full and most appropriate implications are. There are many contributions to MS risk, so we will need a lot more research before it becomes clear what’s really going on.”


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