[Epidemiology of amyotrophic lateral sclerosis]

Epidemiology of amyotrophic lateral sclerosis. Amyotrophic lateral sclerosis (ALS) is the most common motorneuron disease. The incidence of ALS in France is 2.5/100 000 persons-years of follow-up, or 1,500 cases per year. The peak incidence is between 65 and 75 years. The prevalence of ALS is 8/100 000, or 6 000 cases in France with a sex ratio close to 1. The average survival time is close to 36 months after the onset of symptoms, with a large variation between patients. The main prognostic factors are the age of onset, initial site of involvement, the time to diagnosis, respiratory status and nutritional status. 5 to 10% of cases are family related to a mutation of the four major genes SOD1, FUS, TARDP and C9ORF72. In sporadic forms an interaction between a genetic susceptibility factor and an environmental factor is suspected. There is to date no association between exogenous risk factor for sporadic ALS occurrence of which could be demonstrated reproducibly with the notable exception of smoking.