Established risk factors for ALS include:

  • Heredity. Five to 10 percent of the people with ALS inherited it (familial ALS). In most people with familial ALS, their children have a 50-50 chance of developing the disease.
  • Age. ALS most commonly occurs in people between the ages of 40 and 60.
  • Sex. Before the age of 65, slightly more men than women develop ALS. This sex difference disappears after age 70.

It may be that in some people ALS, is triggered by certain environmental factors.

Also, some studies examining the entire human genome (genome-wide association studies) found numerous genetic variations that people with familial ALS and some people with noninherited ALS had in common. These genetic variations might make people more susceptible to ALS.

Environmental factors under study that may modify a person's individual risk of ALS include:

  • Smoking. Smoking cigarettes appears to increase a person's risk of ALS to almost twice that of a nonsmoker. The more years spent smoking, the greater the risk. However, quitting smoking can eventually lower the increased risk.
  • Lead exposure. Some evidence suggests that exposure to lead in the workplace may be associated with the development of ALS.

Military service. Recent studies indicate that people who have served in the military are at higher risk of ALS. Exactly what about military service may trigger the development of ALS is uncertain, but it may include exposure to certain metals or chemicals, traumatic injuries, viral infections and intense exertion.

Apr. 09, 2014