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On the geoepidemiology of Multiple Sclerosis and environmental and infectious determinants of its clinical course

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Simpson Jr,, S (2011) On the geoepidemiology of Multiple Sclerosis and environmental and infectious determinants of its clinical course. PhD thesis, University of Tasmania.

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Abstract

Multiple sclerosis (MS) is a chronic, demyelinating condition of the central nervous system, manifesting in alteration or loss of motor, sensory and cognitive function. The causes of MS are unclear but include genetic and environmental factors. This thesis presents several epidemiologic analyses, examining MS geoepidemiology, locally and globally, as well as evaluating key environmental and infectious determinants of clinical course. The first analysis chapter examines MS epidemiology in the Greater Hobart region of Tasmania over the interval 1951 to 2009. This analysis found a significant increase in prevalence, this mediated by a significantly decreased mortality and increased longevity, as well as evidence of an increasing female/male sex ratio. Next is a meta-analysis of MS prevalence and its association with latitude. This work, utilising the largest collection of MS prevalence studies, found a significant positive association between MS prevalence and latitude. This provides evidence in favour of the latitudinal gradient hypothesis and for environmental factors underlying the gradient, most particularly personal ultraviolet radiation (UVR) exposure and vitamin D. The association between serum 25-hydroxyvitamin D (25(OH)D) and relapse was examined in a prospective cohort with clinically-definite MS followed for 2.3 years. This analysis found a significant inverse association between higher levels of 25(OH)D and subsequent hazard of relapse. This study provides key evidence that is needed to justify conducting randomised clinical trials of vitamin D supplementation in reducing relapse frequency in MS. In this MS cohort, it was also found that persons on interferon-β (IFN-β) therapy had significantly higher 25(OH)D levels and that the association between personal sun exposure and 25(OH)D was stronger compared to those not on IFN-β. Importantly, the above association between 25(OH)D and relapse was only observed for those on IFN-β therapy.

Item Type: Thesis (PhD)
Keywords: multiple sclerosis, epidemiology, vitamin D, human herpesvirus
Additional Information: Copyright the Author
Date Deposited: 13 Dec 2011 23:42
Last Modified: 18 Nov 2014 04:26
URI: http://eprints.utas.edu.au/id/eprint/12508
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