Know Your Risk: ALS

Learn more about amyotrophic lateral sclerosis (ALS), a rare but devastating disease.

child in wheelchair on beach

Updated on March 31, 2022.

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease. It slowly kills the body’s nerve cells responsible for movement, which leads to gradually worsening muscle weakness, paralysis, and eventually death. ALS is also commonly called Lou Gehrig’s disease, named after the Yankees baseball player who retired after he was diagnosed with the disease in 1939.

Most people diagnosed with ALS die roughly two to five years after diagnosis. But some live 10 years or longer, including, famously, physicist Stephen Hawking, who lived with ALS over 50 years after being diagnosed in his twenties. There are drugs to help manage ALS symptoms and prevent complications, but there is no cure.

A rare disease with unknown origins

ALS affects about 6 out of every 100,000 people. Why those six are affected remains mysterious. When it comes to ALS, there are still more questions than answers. Doctors aren’t sure exactly what causes ALS, but there are more than a dozen genetic mutations that may contribute to the disease. In most cases, however, a genetic risk factor isn’t clear, suggesting that other external forces may be involved, according to Terryn Davis, occupational therapist and a care manager in Hawaii for the ALS Association. Davis works with about 70 ALS patients around Hawaii.

“For 10 percent of people with ALS, it's familial, genetic and 90 percent is sporadic,” Davis says. This means most cases do not have a clear genetic cause. Some research indicates environmental factors may play a role in the development of the disease and how quickly it progresses.

“We have about 30 genes that are linked to ALS,” explains Davis. “So, one theory is that many people have the genes, but when something happens, an event or an exposure—that kicks off the gene that starts the ALS.”

Environmental factors linked to ALS

Although more research is needed, some suspected environmental factors for ALS include persistent organic pollutants, smoking, beta-methylamino-l-alanine (a neurotoxin), warfare, pesticides, viruses, and toxins such as heavy metals, radiation, electromagnetic fields, solvents, and, possibly, some types of professional athletics, including soccer and American football. Smoking has been tied to a higher risk, especially in post-menopausal women.

Also on the list are polychlorinated biphenyls, or PCBs—chemicals that were used industrially in the United States until they were banned by the U.S. Environmental Protection Agency (EPA) in 1979.

Being exposed to PCBs is associated with a higher ALS risk. A 2019 study published in Journal of Neurology, Neurosurgery & Psychiatry found that ALS patients with higher levels of PCBs and other environmental pollutants had a faster progression of the disease. The researchers tested the blood of 167 people with ALS for these pollutants. They found that the participants with the highest blood levels of certain persistent organic pollutants, including two types of PCBs, lived for an average of 1 year and 11 months, while those with the lowest levels survived for an average of 2 years and 6 months.

Heavy metals are also tied to ALS risk. Airborne lead appears to be a potential offender, according to a 2022 study published in Science of the Total Environment in which the researchers looked at the zip codes of 26,000 ALS patients around the U.S. These patients were more likely than people without ALS to live in a location where they were exposed to airborne lead, such as emissions from small airplanes. 

Mercury, another heavy metal, has been tied to higher ALS risk in some research, but other studies have found no connection. Scientists are still working to understand the relationship between exposure to environmental toxins and the risk of ALS.

ALS in military service members

One group of people suspected to be at particular risk of developing ALS are military service members. A number of studies have detected higher rates in military personnel, including a 2019 paper published in Military Medicine that clocked a rate of 19.7 cases per 100,000 among post-9/11 veterans deployed in support of conflicts. About 2.4 million people are currently serving on active or reserve duty in the U.S. armed forces.

Researchers don’t know why military service members seem to have higher ALS rates, though the science still isn’t entirely conclusive on the risk difference, if any. Some reasons may include chemical exposure and physical exertion from training. It’s unclear if these apparent increased risks also apply to civilians working for the armed services.

Putting ALS patients in the lead

ALS is an incurable disease, but there are resources available for patients and their families. The ALS Association’s nationwide network of local chapters offers a variety of resources and types of support, including information about ALS support groups, clinics, trials, home care, and even voice banking—a ways for patients whose voices are weakening to create a custom, synthesized voice based on their speech samples.

Davis says that having the highest level of care could extend the lives of those with ALS by as much as nine months. Talk to your healthcare provider (HCP) and work with the ALS Association to learn about the best treatment options and medical facilities in your area.

Davis also advises patients and their families to be proactive. “The way to go is to educate the patients, so that they can go and advocate for themselves,” she says.

People with ALS can do more than they might expect, according to Davis. “The really important thing is to teach people that they don't have to be bedridden. We can get them into wheelchairs,” she says. “There is also that shame factor. And they're scared. It's really scary for them because they are totally dependent on a machine and another human being, and to get out in the community is very scary.”

Above all, Davis says, people with ALS shouldn’t stop living after their diagnosis. She notes that many people with the disease—even those who are not able to walk or stand—can often still attend concerts, go to picnics, travel, and do other things that they enjoy.

Article sources open article sources

Mayo Clinic. Amyotrophic lateral sclerosis (ALS). February 22, 2022.
ALS Association. Understanding ALS. Accessed March 24, 2022.
Westeneng HJ, Al-Chalabi A, Hardiman O, Debray TP, van den Berg LH. The life expectancy of Stephen Hawking, according to the ENCALS model. Lancet Neurol. 2018;17(8):662-663.
Talbott EO, Malek AM, Lacomis D. The epidemiology of amyotrophic lateral sclerosis. Handb Clin Neurol. 2016;138:225-238.
Goutman SA, Boss J, Patterson A, Mukherjee B, Batterman S, Feldman EL. High plasma concentrations of organic pollutants negatively impact survival in amyotrophic lateral sclerosis. J Neurol Neurosurg Psychiatry. 2019;90(8):907-912.
Andrew A, Zhou J, Gui J, et al. Airborne lead and polychlorinated biphenyls (PCBs) are associated with amyotrophic lateral sclerosis (ALS) risk in the U.S. Sci Total Environ. 2022;819:153096.
Hoffman HI, Bradley WG, Chen CY, Pioro EP, Stommel EW, Andrew AS. Amyotrophic Lateral Sclerosis Risk, Family Income, and Fish Consumption Estimates of Mercury and Omega-3 PUFAs in the United States. Int J Environ Res Public Health. 2021;18(9):4528. Published 2021 Apr 24.
Parkin Kullmann JA, Pamphlett R. A Comparison of Mercury Exposure from Seafood Consumption and Dental Amalgam Fillings in People with and without Amyotrophic Lateral Sclerosis (ALS): An International Online Case-Control Study. Int J Environ Res Public Health. 2018;15(12):2874.
Andrew AS, O'Brien KM, Jackson BP, et al. Keratinous biomarker of mercury exposure associated with amyotrophic lateral sclerosis risk in a nationwide U.S. study. Amyotroph Lateral Scler Frontotemporal Degener. 2020;21(5-6):420-427.
Beard JD, Kamel F. Military service, deployments, and exposures in relation to amyotrophic lateral sclerosis etiology and survival. Epidemiol Rev. 2015;37(1):55-70.
Sagiraju HKR, Živković S, VanCott AC, et al. Amyotrophic Lateral Sclerosis Among Veterans Deployed in Support of Post-9/11 U.S. Conflicts. Mil Med. 2020;185(3-4):e501-e509.
McKay KA, Smith KA, Smertinaite L, Fang F, Ingre C, Taube F. Military service and related risk factors for amyotrophic lateral sclerosis. Acta Neurol Scand. 2021;143(1):39-50.
ALS Association. Resources for Learning About ALS. Accessed March 25, 2022.
Lacorte E, Ferrigno L, Leoncini E, Corbo M, Boccia S, Vanacore N. Physical activity, and physical activity related to sports, leisure and occupational activity as risk factors for ALS: A systematic review. Neurosci Biobehav Rev. 2016;66:61-79.
Luna J, Logroscino G, Couratier P, Marin B. Current issues in ALS epidemiology: Variation of ALS occurrence between populations and physical activity as a risk factor. Rev Neurol (Paris). 2017;173(5):244-253.
United States Environmental Protection Agency. Learn about Polychlorinated Biphenyls (PCBs). Accessed March 29, 2022.


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