State of the art: According to the available previous studies, France is considered a zone of medium to high risk of multiple sclerosis (MS) with an estimated overall prevalence of at least 50/100,000 inhabitants, incidence rates were stable in some areas but increased over time in others and a strong ethnic effect on the incidence, clinical presentation, and course of MS is reported.
Results: Based on two health insurance survey the prevalence has been deduced. At January 1, 2003 from the data of agricultural health insurance the prevalence is evaluated at 65.5/100,000 inhabitants (95p.cent CI=62.5-67.5) with a gradient of North East towards South-West. The data from the national health insurance were very near. During the period 2000-2004, recent studies in Auvergne and Brittany demonstrated an annual incidence comprising between 4.2 and 5.1 per 100,000 inhabitants. In Lorraine, in a large population-based study, in December 31, 2004 the prevalence rate was 120/100,000 (95p.cent CI: 119 to 121). During the period 1990-2002, the average age- and sex-adjusted annual incidence rate was 5.5/100,000 (95p.cent CI: 4.4-6.6). In Lorraine, we found that the age-adjusted incidence rate increased during the period 1990-2002. The incidence of MS in women increased, whereas that in men did not change significantly during this period. Similarly, in Norway, North Ireland and Denmark, the incidence among women increased the most. The clinical features of MS were compared in 211 North Africans patients and 2 945 Europeans patients in two French MS centres (Lorraine and Nice) with definite MS according to McDonald's criteria. The course of MS appears more aggressive in North Africans than in Europeans patients. For example, we demonstrated a shorter time to reach the Expanded Disability Status Scale score of 4.0 (p=0.001) or 6.0 (p<0.0001) in North Africans patients.
Perspectives and conclusions: The incidence rates found in these studies were comparable to those reported in several European populations. This undoubtedly places France in the category of regions with a high risk zone of MS. The incidence of MS in women increased; thus, exogenous (or epigenetic) factors vary over time and may affect men and women differently. The course of MS appears more aggressive in North Africans than in Europeans patients.