August 8, 2003
Source: British Medical Journal (BMJ)
By Joene Hendry
Higher levels of sun exposure during childhood and early adolescence and greater actinic damage are associated with a reduced risk of developing multiple sclerosis, according to results from the study of a population from Tasmania.
A. F. van der Mei, a PhD student from the University of Tasmania, Hobart, Australia, and colleagues examined past sun exposure in 136 residents of Tasmania, younger than 60 years of age, with confirmed multiple sclerosis. They compared these data with past sun exposure levels in 272 age and gender matched controls. Overall, 68% of the cases were female and 95% of the study participants were born in Tasmania and lived there at age 10.
Participants answered questions regarding life-long sun exposures, sun exposure protective measures and vitamin D supplements used, as well as medical history. The researchers correlated these data with past calendar measures of sunshine at Tasmania's latitude.
The researchers found that greater levels of actinic damage, measured from the skin surface of participant's hands, were associated with a reduced risk for developing multiple sclerosis - adjusted odds ratios of 0.32, 0.33, and 0.17 for grade 4, 5, and 6, respectively, when compared with grade 3 multiple sclerosis.
Additionally, higher sun exposure, consisting of 2 to 3 hours or more on average per day during the summer weekends and holidays while study participants were 6 to 15 years old, was associated with a decreased risk of developing multiple sclerosis (adjusted odds ratio of 0.31). Conversely, high levels of sun exposure obtained during the 1, 5, and 10 year period prior to developing multiple sclerosis did not show any evidence of a protective effect.
The authors conclude, "The finding of no association between sun exposure in the decade before onset of multiple sclerosis may indicate that the timing of low exposure may relate more to age related immunological development than to onset of disease."
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