Multiple sclerosis

This chapter describes the incidence and prevalence of multiple sclerosis (MS) and shows the uneven distribution across the world. Despite differences in diagnostic criteria over time and considerable variation in methodology the prevalence is higher in northern Europe, the northern part of North America, Australia, and New Zealand compared to the rest of the world. There is an unexplained increase in both incidence and prevalence across the world. The increased life expectancy correlates with the general increase in life expectancy and is so far neither explained by better diagnostics nor new treatments. Epidemiological studies are essential for our understanding of disease susceptibility and progression, and essential for planning of healthcare. Future studies should be large, methodologically sound, and comparable to enable comparisons across countries and regions.