Geographical Clues About Multiple Sclerosis

Multiple sclerosis (MS) is a progressive neurological disease of unknown cause. Investigators are attempting to discover its cause through laboratory investigation and through population-based epidemiologic analysis. Much of the most intriguing evidence comes from an analysis of the geography of MS. Its incidence, prevalence, and mortality rates are lowest at the equator and increase regularly with latitude. Moreover, people who migrate from high to low incidence areas at an early age assume the risk of developing MS of their destination region, while those migrating in adulthood retain the risk of their countries of origin, implicating an agent or agents, in childhood. Cultural and economic factors may be important as well. Despite these clues, identification of the cause of MS remains elusive.