Around half of people with ALS die within 30 months of their symptoms beginning, and about 20% of people with ALS live between five and ten years after symptoms begin. Guitarist Jason Becker has lived since 1989 with the disorder, while cosmologist Stephen Hawking lived for 55 more years following his diagnosis, but they are considered unusual cases. Cause
Though the exact cause of ALS is unknown, genetic and environmental factors are thought to be of roughly equal importance. The genetic factors are better understood than the environmental factors; no specific environmental factor has been definitively shown to cause ALS. A liability threshold model for ALS proposes that cellular damage accumulates over time due to genetic factors present at birth and exposure to environmental risks throughout life. Genetics
ALS can be classified as familial or sporadic, depending on whether or not there is a family history of the disease. There is no consensus among neurologists on the exact definition of familial ALS. The strictest definition is that a person with ALS must have two or more first-degree relatives (children, siblings, or parents) who also have ALS. A less strict definition is that a person with ALS must have at least one first-degree or second-degree relative (grandparents, grandchildren, aunts, uncles, nephews, nieces or half-siblings) who also has ALS. Familial ALS is usually said to account for 10% of all cases of ALS, though estimates range from 5% to 20%.
Men have a higher risk mainly because spinal-onset ALS is more common in men than women. The number of those with ALS in the United States in 2015 was 5.2 people per 100,000, and was higher in whites, males, and people over 60 years old. The number of new cases is about 0.8 people per 100,000 per year in east Asia and about 0.7 people per 100,000 per year in south Asia. About 80% of ALS epidemiology studies have been conducted in Europe and the United States, mostly in people of northern European descent. There is not enough information to determine the rates of ALS in much of the world, including Africa, parts of Asia, India, Russia, and South America. There are several geographic clusters in the Western Pacific where the prevalence of ALS was reported to be 50–100 times higher than the rest of the world, including Guam, the Kii Peninsula of Japan, and Western New Guinea. The incidence in these areas has decreased since the 1960s; the cause remains unknown.People of all races and ethnic backgrounds may be affected by ALS, but it is more common in whites than in Africans, Asians, or Hispanics. In the United States in 2015, the prevalence of ALS in whites was 5.4 people per 100,000, while the prevalence in blacks was 2.3 people per 100,000. The Midwest had the highest prevalence of the four US Census regions with 5.5 people per 100,000, followed by the Northeast (5.1), the South (4.7), and the West (4.4).