This study was undertaken to investigate whether exposure to the sun in the near or distant past and the level of vitamin D in blood are linked to “first demyelinating events” (FDE), in different regions of Australia. First demyelinating events are generally the warning signs of development of the severely debilitating nerve disease, Multiple Sclerosis (MS). The results of the study revealed that high exposure to the sun in the distant as well as in the recent past can reduce the risk of FDE. High blood levels of vitamin D are also associated with lowering FDE risk.
There have been studies that link high blood levels of vitamin D and high intake of the same to a lower risk of MS. However, none of the previous studies has quantitatively linked the amount of sun exposure to risk of MS and also qualified the effects of living in different latitudes (predicting sun exposure) on the risk of MS. This study was a large observation over different areas of Australia, which looked into personal sun exposure in the last latitudinal area of residence and the risk of FDEs.
* For this study, 216 patients with FDEs, between ages 18 and 59, were included. Matching control healthy volunteers (395 in number) were also selected. Both cases and controls were similar in age, gender and area of residence.
* The study was conducted at four regions in Australia, which lay between latitudes 27°S and 43°S.
* All the participants were asked questions regarding their previous sun exposure. Their skin type was examined and blood was tested for vitamin D levels.
* Higher sun exposure translated to a higher blood level of vitamin D and lower risk of FDE. However, FDE risk was not associated with history of sunburn.
* Those with FDE had lower blood levels of vitamin D.
* In 34.3 percent of FDE patients who took vitamin D supplements, vitamin D levels in the blood remained low.
* The incidence of FDE at 27°S was 2.1 per 100,000 per year, during November 1, 2003 to December 31, 2006; whereas, it was 8.7 per 100,000 at 43°S. This rise over latitudes is four-times greater.
The authors agree that there may be errors in the self-reports of sun exposure. Another limitation was the fact that sun exposure before the age of 6 years was not taken into consideration. Also, vitamin D levels were measured only at one point. Long-term measurement and status of vitamin D levels might have given more insight into the link between raised risk of FDEs and vitamin D levels in an individual.
This study showed that exposure to the sun in the near or distant past raises the levels of vitamin D and reduces the risk of FDEs, and thus MS, in individuals. The incidence of FDE also varies to a great extent with a shift in latitudes. Since an FDE is thought to be a precursor of MS, this study is crucial for research in MS. Another important finding of this study is the fact about the lack of benefit to the blood vitamin D level with supplements alone. The authors thus conclude, “Advocating vitamin D supplementation alone may be a less effective preventive intervention than has been suggested by previous epidemiologic studies” and exposure to sun may be a better answer to MS prevention.
For More Information:
Sun Exposure and Vitamin D are Independent Risk Factors for CNS Demyelination
Publication Journal: Neurology, February 2011
By R M Lucas, PhD; A-L Ponsonby, PhD; Australian National University, Canberra, Australia; Murdoch Children’s Research Institute, Melbourne, Australia
*FYI Living Lab Reports Are Summaries of the Original Research.