Solar rays incidence on the prevalence of multiple sclerosis and its correlation with Brazil's macroregions: A systematic review and metanalysis

Multiple sclerosis (MS) is a chronic neurodegenerative disease of inflammatory and demyelinating nature, whose global distribution presents marked heterogeneity. International studies indicate a higher prevalence of MS in regions with lower incidence of solar radiation, which has been associated with reduced synthesis of vitamin D. In Brazil, however, there are few studies correlating the prevalence of the disease with geographic and environmental variables. To assess the prevalence of multiple sclerosis in Brazilian macroregions and to verify possible correlations with latitude, longitude, and mean annual solar radiation levels. A systematic search was conducted in the PubMed, Scopus, Web of Science, LILACS and SciELO databases, using the descriptors "multiple sclerosis", "prevalence" and "Brazil". Observational studies that reported prevalence data in Brazilian regions were included. The information was quantitatively synthesized and submitted to correlation analysis and meta-analysis based on geographic coordinates and solar radiation data. Thirty-four studies were included, covering the five macroregions of the country. The prevalence of MS showed wide regional variation, with higher values in the South and Southeast regions. However, no statistically significant correlations were observed between the prevalence of MS and the geographic parameters analyzed, including solar incidence. The findings reveal that in Brazil there is no relationship between the latitudinal gradient and the prevalence of MS, suggesting the influence of sociocultural, genetic and environmental factors specific to the country. Thus, the need for more comprehensive epidemiological studies in areas that are still little investigated is evident.