The relation of ultraviolet radiation and multiple sclerosis in Newfoundland

Background. It has been thought that the occurrence of multiple sclerosis (MS) could be associated with daily ultraviolet exposure. In this study we investigated the geospatial association between average daily ultraviolet B (UVB) irradiance and MS prevalence in Newfoundland and Labrador (NL), Canada. Methods: A complete list of patients diagnosed with MS in the province of NL was constructed. Places of habitation from birth to diagnosis were ascertained by mailout survey. Results: A 74% rate of return on the survey results was obtained. A plot of the average daily erythemal UV over the available five years (1998-2002) shows that the distribution of MS follow a north-south gradient. Average daily UVB measurements are lower in the higher latitudes. A statistically significant negative correlation of MS incidence with erythemal UVB was found that is stronger than the correlation using latitude. This correlation appears to be strongest in the first year of life and declines when subsequent years are examined up to age ten. No significant correlation was found for the subjects' locale of habitation at the time of their first MS attack. Conclusions: This study suggests that UVB radiation may contribute to the pathogenesis of MS.