ALS is one of the most common neuromuscular diseases worldwide, and people of all races and ethnic backgrounds are affected. One or two out of 100,000 people develop ALS each year. ALS most commonly strikes people between 40 and 60 years of age, but younger and older people can also develop the disease. Men are affected slightly more often than women.
Although the incidence of ALS is thought to be regionally uniform, there are three regions in the West Pacific where there has in the past been an elevated occurrence of ALS. This seems to be declining in recent decades. The largest is the area of Guam inhabited by the Chamorro people, who have historically had a high incidence (as much as 143 cases per 100,000 people per year) of a condition called Lytico-Bodig disease which is a combination of symptoms similar to ALS, parkinsonism, and dementia. Lytico-Bodig disease has been linked to the consumption of cycad seeds and in particular, the chemical found in cycad seeds, β-methylamino-L-alanine (BMAA). Two more areas of increased incidence are West Papua and the Kii Peninsula of Japan.
Although there have been reports of several "clusters" including three American football players from the San Francisco 49ers, more than fifty football players in Italy, three football-playing friends in the south of England, and reports of conjugal (husband and wife) cases in the south of France, these are statistically plausible chance events. Although many authors consider ALS to be caused by a combination of genetic and environmental risk factors, so far the latter have not been firmly identified, other than a higher risk with increasing age.
Read more about this topic: Amyotrophic Lateral Sclerosis