Clustering of multiple sclerosis, age of onset and gender in Sardinia

In diseases with unpredictably long latent period, such as multiple sclerosis (MS), cluster studies, and the analysis of disease distribution by gender and age of onset, can provide clues to disease etiopathogenesis. Sardinia, insular Italy, is among the regions at highest risk for MS worldwide. Multiple epidemiological evidences favour the role of exogenous factors in modulating MS incidence in Sardinians. Its steady increase over time is the main determinant for the observed increased prevalence of MS. Incidence is especially increasing for MS with RR initial course, in individuals with older age and in the female population. More women that will develop MS are believed to being born now. Early childhood is likely the age of susceptibility to MS, and especially in women, in most recent cases, and in individuals developing MS at earlier age and with RR initial clinical course. These evidences suggest that specific exogenous (gender-related? perinatal?) factors have recently been exerting as determinants of the MS increase in Sardinians and the change of its phenotype. Such factors are unlikely agents with fixed latency incubation period, but they could rather be the result of recent lifestyle changes and/or of their interplay with a highly susceptible genetic background.