Regional variation in multiple sclerosis prevalence in Australia and its association with ambient ultraviolet radiation

The aim of this study was to conduct an ecological analysis of the extent t o which ultraviolet radiation (UVR) levels might explain the regional varia tion of multiple sclerosis (MS) in Australia. MS prevalence data for six Au stralian regions were compared with UVR levels of the largest city in each region, with some other climatic variables and with the melanoma incidence in the same regions. A close association was found between the theoretical MS prevalence predicted from UVR levels and the actual prevalence. Furtherm ore,the negative correlation between UVR and MS prevalence (r = -0.91, p = 0.01) was higher than the positive correlation observed for UVR and maligna nt melanoma incidence (r = 0.75, p = 0.15 for males and r = 0.80, p = 0.10 for females). This study demonstrated that the regional variation in MS pre valence in the continent of Australia could be closely predicted by regiona l UVR levels. It is consistent with the hypothesis that UVR exposure may re duce the risk of MS possibly via T-lymphocyte-mediated immunosuppression. A nalytical epidemiology studies are required to investigate this specific hy pothesis. Copyright (C) 2001 S. Karger AG, Basel.