Epidemiology of Amyotrophic Lateral Sclerosis in the Pays de la Loire, France: A 20-Year Study from a Centralized Diagnostic Center

INTRODUCTION: Amyotrophic lateral sclerosis (ALS) is a fatal motor neurons disease with multifactorial etiology. The epidemiology of ALS in France is mainly documented through the Limousin regional registry (FRALim). We aimed to determine the incidence and clinical characteristics of ALS cases over a 20-year period in another French region, the Pays de la Loire, served by a single centralized diagnostic center. METHODS: All patients diagnosed with ALS at the Angers University Hospital reference center between 2003 and 2023 were retrospectively included. Demographic and clinical data were extracted from medical records, and incidence rates were calculated using annual population estimates from the National Institute of Statistics and Economic Studies. Spatial analyses were performed to identify over-incidence areas and potential environmental or occupational determinants. RESULTS: A total of 1,316 patients were diagnosed with ALS during the study period, corresponding to a crude incidence rate of 1.88 cases per 100,000 person-years (95% CI: 1.78-1.98), with no significant variation over time. The standardized incidence rate was 1.73 (95% CI: 1.63-1.83). The mean age at symptom onset was 63.6 ± 11.2 years, 58.7% of patients were male. The mean disease duration was 3.7 ± 3.5 years. ALS onset was spinal in 70.3%, bulbar in 27.9%, and respiratory in 1.7% of cases. Familial or genetic forms accounted for 6% of patients. Four geographical over-incidence areas were identified, with no correlation found with pesticide use, air pollution, or other environmental indicators. One occupational cluster was observed among farmers in a specific commune, prompting a dedicated investigation. CONCLUSION: This 20-year retrospective study provides the first epidemiological data on ALS in western France. The incidence and clinical features are consistent with national and European data. The identification of spatial and occupational clusters underlines the importance of continued regional surveillance and of prospective, registry-based studies to clarify environmental and occupational risk factors for ALS.