Although ALS is considered to be a rare disease, it is in fact one of the most common neuromuscular diseases worldwide.
The prevalence of ALS (i.e. the number of patients with ALS at any given point in time is relatively low (6-8/100000 of the population) compared to other neurodegenerative disorders, which is a reflection of the relative short duration of disease in ALS. This translates into a patient population of approximately 6000-8000 patients at any given time in a country like France (> 60 million people).
However, the relatively low prevalence ALS does not reflect the actual incidence of the disease (i.e. the number of people that are diagnosed with ALS each year). Thus, the incidence of ALS in now estimated at 2.5/100000 of the population per year.
The incidence of 2.5/100000/year for ALS is therefore comparable with that of Multiple Sclerosis in most European countries. Thus taking the French population as an example, the lifetime risk of developing ALS is 1:700.
The onset of ALS is most commonly between the ages of 40 and 60 years of age, and is slightly more common in men than women.