Why do people develop ALS?

A small number (10 per cent or less) of people with ALS have familial (or hereditary) ALS. The rest (90% or more) of ALS cases are random (or sporadic). As the name “random” implies, anyone can develop ALS, including young adults and the elderly.

On average, the first symptoms of ALS begin to show up in the mid- to early senior years. It is most commonly diagnosed between the ages  of 40 and 70. ALS is diagnosed in both men and women of all ethnic and socio-economic groups.

Risk factors

Most of the risk factors for ALS are things that you can’t do anything about:

  • Genetics: There are several genetic mutations linked to ALS. These include SOD1, C9ORF72, TDP-43 and FUS.
  • Age: The risk of developing ALS increases with age.
  • Heredity: Most people with the familial form of ALS have a 50 per cent chance of passing the disease to each child.
  • Smoking: Smoking is the only environmental factor to be recognized as having a direct influence on increasing the risk of developing ALS.

Content adapted from the ALS Guide, which was published in 2019 as a joint project of ALS Societies across Canada.