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Abstract
Objectives: To examine whether past and recent sun exposure and vitamin D status (serum 25-hydroxyvitamin D [25(OH)D] levels) are associated with risk of first demyelinating events (FDEs) and to evaluate the contribution of these factors to the latitudinal gradient in FDE incidence in Australia.
Methods: This was a multicenter incident case-control study. Cases (n = 216) were aged 18–59 years with a FDE and resident within one of 4 Australian centers (from latitudes 27°S to 43°S), from November 1, 2003, to December 31, 2006. Controls (n = 395) were matched to cases on age, sex, and study region, without CNS demyelination. Exposures measured included self-reported sun exposure by life stage, objective measures of skin phenotype and actinic damage, and vitamin D status.
Results: Higher levels of past, recent, and accumulated leisure-time sun exposure were each associated with reduced risk of FDE, e.g., accumulated leisure-time sun exposure (age 6 years to current), adjusted odds ratio (AOR) = 0.70 (95% confidence interval [CI] 0.53–0.94) for each ultraviolet (UV) dose increment of 1,000 kJ/m2 (range 508–6,397 kJ/m2). Higher actinic skin damage (AOR = 0.39 [95% CI 0.17–0.92], highest grade vs the lowest) and higher serum vitamin D status (AOR = 0.93 [95% CI 0.86–1.00] per 10 nmol/L increase in 25(OH)D) were independently associated with decreased FDE risk. Differences in leisure-time sun exposure, serum 25(OH)D level, and skin type additively accounted for a 32.4% increase in FDE incidence from the low to high latitude regions.
Conclusions: Sun exposure and vitamin D status may have independent roles in the risk of CNS demyelination. Both will need to be evaluated in clinical trials for multiple sclerosis prevention.
Footnotes
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Study funding: Supported by 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.
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- AOR
- adjusted odds ratio
- CI
- confidence interval
- EAE
- experimental allergic encephalomyelitis
- FCD
- first clinical diagnosis of CNS demyelination
- FDE
- first demyelinating event
- MS
- multiple sclerosis
- OR
- odds ratio
- PPMS
- primary progressive multiple sclerosis
- UV
- ultraviolet
- Received August 2, 2010.
- Accepted October 7, 2010.
- Copyright © 2011 by AAN Enterprises, Inc.
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