It’s rare, affecting about 5.2 people per 100,000 in the U.S. population, according to the National ALS Registry. https://www.webmd.com/brain/who-gets-als
On average, people with ALS (PALS) die due to respiratory failure 2 to 4 years after the onset of symptoms. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8380909/
About 10% of those with the condition will live 10 years, and 5% will live for 20 or more years. https://www.verywellhealth.com/als-lou-gehrigs-disease-life-expectancy-2223973
Unfortunately, the prognosis for ALS is poor. ALS is a progressive condition that is terminal within five years for 80% of the people impacted by it. https://www.verywellhealth.com/als-lou-gehrigs-disease-life-expectancy-2223973
Generally, ALS is categorized in one of two ways: Upper motor neuron disease affects nerves in the brain, while lower motor neuron disease affects nerves coming from the spinal cord or brainstem. In both cases, motor neurons are damaged and eventually die. ALS is fatal. The average life expectancy after diagnosis is two to five years, but some patients may live for years or even decades. (The famous physicist Stephen Hawking, for example, lived for more than 50 years after he was diagnosed.) There is no known cure to stop or reverse ALS.
Each person with ALS experiences a different proportion of upper and lower motor neurons that die. This results in symptoms that vary from person to person. https://www.hss.edu/condition-list_amyotrophic-lateral-sclerosis.asp
2-Minute Neuroscience: Amyotrophic Lateral Sclerosis (ALS) 2017/03/14 Neuroscientifically Challenged