Researchers demonstrate a potential association between monthly ambient sunlight, infections and relapse rates in Multiple Sclerosis (Neuroepidemiology 2008, 31: 271-279)
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Medical Update Memo
November 13, 2008
Summary
Monthly variation in multiple sclerosis (MS) relapses has been found. However, the relationship between seasonal environmental factors, infections, serum vitamin D [25(OH)D] and MS relapses is undetermined. Dr. Helen Tremlett from the University of British Columbia and colleagues studied a group of people with relapsing-remitting (RR) MS patients in Southern Tasmania for approximately 2 years. Their objective was to determine if monthly ambient environmental factors, estimated serum 25(OH)D, upper respiratory tract (URT) infections and relapse rates were associated. This work was funded in part by the MS Society of Canada.
Details
Over the course of 2 years, researchers measured the total ultraviolet radiation modulated by human skin, (erythemal ultraviolet radiation or EUV), the occurrence of relapses,and infections monthly. They also tracked the total amount of serum 25(OH)D .. The body produces 25(OH)D with exposure of bare skin to ultraviolet radiation, which is then ultimately converted into vitamin D3..
It was determined that the lowest relapse rate occurred in February (mid-late summer in Tasmania) versus March-January (Tasmainian winter). Monthly relapse rates correlated with: (1) prior exposure to ultraviolet light, (lag time 1.5 months); (2) Upper respiratory tract (URT) infection rates (no lag); (3) 25(OH)D (no lag). The association between URT infections and relapses was reduced after adjustment for monthly EUV.
This study demonstrates that relapse rates are inversely associated with EUV and serum 25(OH)D levels and positively associated with URT infections. The lag time observed between EUV but not 25(OH)D and relapse rates is consistent with a role for EUV-generated 25(OH)D in the alteration of relapse rates. This study suggests that low exposure to ambient sunlight and low serum 25(OH)D are associated with relapses in MS. Future work should consider the observed association and the complex interrelationship between UV, vitamin D, infections and relapse rates.
National Research and Programs
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Disclaimer
The Multiple Sclerosis Society of Canada is an independent, voluntary health
agency and does not approve, endorse or recommend any specific product or therapy,
but provides information to assist individuals in making their own decisions.
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