Migration and multiple sclerosis: The French West Indies experience

The French West Indies (FWI), i.e., the islands of Martinique and Guadeloupe, have recently experienced the emergence of multiple sclerosis (MS). This epidemiological upheaval followed a return migration of the FWI population that had previously migrated to continental France. The prevalence MS was 14.8/10(5) (95% CI: 11.9-17.7) on Dec. 31, 1999 and its mean annual incidence was 1.4/10(5) (95% CI: 1.0-1.8) for the period July 1997 to June 2002. The prevalence of MS in Martinique, that received more return migration, is higher than that of Guadeloupe (21.0/10(5) VS. 8.5/10(5)). This emergence of MS has been accompanied also by an inversion of its clinical spectrum, with recurrent neuromyelitis optica accounting for only 17.8% of cases. The standardized ratio of the incidence of MS among migrants is 1.71 (95% CI: 1.19-2.38;P<0.01) and if migration to continental France occurred before the age of 15 it is 4.05 (95% CI: 2.17-6.83;P<0.0001). According to recent data, a drastic reduction in exposure to sunlight and to intestinal parasites during childhood, found preferentially among migrants, are possible environmental factors responsible for this emergence. (c) 2007 Elsevier B.V. All rights reserved.