The incidence of MND is approximately 1–5 out of 100,000 people. Men have a slightly higher incidence rate than women. Approximately 5,600 cases are diagnosed in the U.S. every year. By far the greatest risk factor is age, with symptoms typically presenting between the ages of 50-70. Cases under the age of 50 years are called "young onset MND", whilst incidence rates appear to tail off after the age of 85.

There are three "hot spots" of MND in the world. One is in the Kii peninsula of Japan, one amongst a tribal population inPapua New Guinea. Chamorro inhabitants from the island of Guam in the Pacific Ocean have an increased risk of developing a form of MND known as Guamanian ALS-PD-dementia complex or "lytico bodig", although the incidence rate has declined over the last 50 years and the average age of onset has increased.[10]Putative theories involve neurotoxins in the traditional diet including cycad nut flour and bats that have eaten cycad nuts.[11][12]