Amyotrophic Lateral Sclerosis Prevalence Projection in 2040: A Less Rare Disease

Objective: To project ALS prevalence across multiple countries through 2040, accounting for both population aging and increased survival. Methods: Data from the Piemonte and Valle d'Aosta ALS register (PARALS) was used to estimate the trends in incidence and prevalence from 2005 to 2019. Survival trends over this period were also assessed. The observed annual increase was then projected into future years up to 2040. Concurrently, the incidence for each future year was calculated using population projections. Finally, the prevalence rate for each year was estimated as the product of the projected incidence and the projected survival. We also estimated survival for fifteen countries by dividing prevalence by incidence, based on available data, and applied the same increase observed in PARALS to project prevalence in these countries up to 2040. Results: Using data from 3294 patients, we determined that ALS survival increased by 0.06 years annually from 2005 to 2019 in Piemonte and Valle d'Aosta. Considering changes in incidence due to population aging, the prevalence is projected to reach 15.72 per 100,000 population by 2040 in this area, while rising by a median of 24.9% across multiple countries worldwide. If a new drug could provide a 6-month increase in survival starting in 2025, disease prevalence would rise by 37.8% by 2040. We provided a web interface so users can model different data and assumptions. Interpretation: ALS prevalence is projected to increase significantly over the next decades. This underscores the need for careful planning and allocation of public health resources.