Mom's Story, A Child Learns About MS

Mom's Story, A Child Learns About MS
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Tuesday, March 1, 2011

MS and sunlight

Higher levels of sun exposure and higher blood levels of vitamin D were both associated with decreased risk of having a first demyelinating event that can be the first indicator of multiple sclerosis, in a comprehensive study undertaken in Australia, called the Ausimmune Study. (A first demyelinating event, in this study called FDE, is also known as clinically isolated syndrome (CIS), a first neurologic episode caused by inflammation/demyelination in the brain or spinal cord.) Some of these individuals developed MS during the study and others did not, however findings were similar in either case. Robyn Lucas, PhD, Anthony McMichael, PhD (The Australian National University, Canberra) and colleagues across Australia report their findings in Neurology (2011;76:540-548). This study was supported by the National MS Society, the National Health and Medical Research Council of Australia, the ANZ William Buckland Foundation, and MS Research Australia.

The findings provide additional support for previous suggestions that sun exposure and vitamin D may help protect against developing MS. It remains to be seen whether safe and effective strategies can be developed that utilize this potential protection without the risks involved in overexposure to the sun or overdoses of vitamin D supplements, and whether these findings have relevance for individuals who already have MS.

Background: In all parts of the world, MS is more common at latitudes that are farther from the equator and less common in areas closer to the equator. This latitude effect has been under investigation for many years. Previous studies have found evidence suggesting that higher lifetime exopsure to sunlight (through which the skin makes vitamin D) and higher blood levels of vitamin D may reduce a person’s risk of developing MS. This is an active area of continued research.

The Ausimmune study was undertaken to investigate whether increased exposure to sunlight in those living closer to the equator and the vitamin D that is produced in part by sunlight may be protective against MS. Rather than studying people who had already been diagnosed with definite MS, which could alter a person’s lifestyle and recollection of past events, the team investigated sun exposure and vitamin D levels in people who had not yet been diagnosed with MS, but who had experienced a CIS. A CIS often, but not always, leads to a diagnosis of MS.

The Study: The investigators recruited participants who were aged 18–59 years and lived in four geographic regions of Australia between November 1, 2003, and December 31, 2006. The four regions were characterized by differing distance from the equator. A total of 216 people were enrolled who had experienced a CIS. A total of 395 controls were randomly selected from the Australian Electoral Roll and matched to the CIS cases in age, gender, and study region.

Sun exposure was measured in several ways, including by participant reports on how much time they spent in the sun during different periods of life starting from age 6, and also by more objective means, such as examination of the skin for sun damage (actinic skin damage) and measurements of skin pigment (melanin). The latitude and longitude of participants’ residence were also recorded as an indicator of ambient ultraviolet (UV) light. Vitamin D levels were measured by a blood sample taken at entry into the study.

The results show that higher recent or lifetime sun exposure and higher blood levels of vitamin D at study entry were independently linked with a reduced risk of CIS. The investigators reported that people with most evidence of skin damage from sun exposure were 60% less likely to develop a CIS than those with the least damage. People with the highest levels of vitamin D at entry also were less likely to have a CIS than those with the lowest levels. As reported in other parts of the world, this study confirmed a latitude effect in Australia. Taken together, differences in sun exposure, vitamin D levels, and skin type accounted for a 32.4% increase in CIS incidence from the low to high latitude regions of Australia.

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