Many things about amyotrophic lateral sclerosis (ALS), also known as Lou Gehrig’s disease, remain unclear. Without knowing exactly what causes ALS, it’s hard to tell why some people get the disease while others don’t. Researchers do have some possible ideas, however.
ALS disrupts your motor neurons. These are nerve cells that control important muscle activities, including breathing, talking, swallowing, and walking. Over time, the loss of muscle control becomes worse.
There is no cure for ALS, although research is ongoing. There are no preventive steps either.
It’s rare, affecting about 3.9 people per 100,000 in the U.S. population, according to the National ALS Registry. Because of the seemingly random nature of the condition, it’s hard for researchers to pinpoint who might have a greater chance of getting it.
ALS by Sex, Race, Age, Family
Doctors have learned some things from people who have this condition:
● Sex: About 60% of people with ALS are male.
● Race: 93% of people with it are white.
● Aging: An ALS diagnosis usually happens between the ages of 40 and 60. Most people get a diagnosis in their mid-50s. You can get it earlier, though having it before 30 is very rare.
● Family history: A small percentage of ALS cases are passed down from family.
Types of ALS
There are two main kinds, depending on whether the disease runs in your family.
● Sporadic: This makes up 90% to 95% of all ALS cases, as it occurs in people who have no known family history of the disease nor any clear things that would make them more likely to get it. Other family members are not expected to be at risk for inheriting ALS in sporadic cases.
● Familial: In about 5% to 10% of cases, ALS runs in the family. If you have familial ALS, there is a 50% chance that your children will get it as well.
The Role of Genes
Scientists are looking into whether genetics, things in the environment, or a combination of both cause ALS.
Some theories suggest people who might already be genetically at risk for ALS get the disease after some kind of contact with an outside “trigger” in their environment, such as being around a toxin.
Scientists have found over a dozen mutations in genes that have ties to ALS, but the two major ones are C9orf72 and SOD1 genes.
C9orf72 gene: Mutations in the gene known as C9orf72 have been found in about a third of all familial cases and a small percentage of sporadic ones. Scientists have also found that this defect on the C9orf72 gene is tied to what’s called “frontotemporal dementia (FTD),” an uncommon form of dementia. Some researchers think that ALS and some forms of FTD are related.
SOD1 gene: Mutations on this gene appear in about 20% of familial cases and 1% to 5% of sporadic ones. It’s unclear how the mutations lead to ALS. Research has found that the proteins from a mutated SOD1 gene can become toxic.
Scientists are also looking at whether things in the environment such as chemicals and other agents can raise your chances of getting ALS. But it’s been hard for them to prove anything specific so far. Some things they are looking into:
Smoking: Smoking is believed to be the only probable factor that may raise your chances for ALS. But this may be true mainly for women, especially those after menopause. This link is controversial among doctors.
Contact with toxins: Lead and other chemicals may be linked to ALS, but no single agent has been consistently found to be a cause.
Military service: Studies have found that military veterans, especially those deployed during the Gulf War in 1991, have a greater chance of ALS. The exact causes remain unclear, but may include contact with chemicals or metals, injuries, infections, or the intense physical activity needed to serve. Those who were in the Gulf War are more likely to get ALS compared with other veterans.
Intense activity: The most famous person to have ALS was Lou Gehrig, the baseball player who died from it. Studies have shown a higher chance among athletes, who are very active. But the studies have been small, so it’s too early to say that being an athlete means you have a greater chance of getting the condition.
Your work: Several lines of work -- including sports, cockpit, construction, farm, hairdressing, lab, veterinary, and welding, among many others -- have been reported to carry a higher chance of ALS. These jobs often involve some kind of contact with pesticides, metals, and chemicals. But the common, underlying risk has not been found.
Where you live: Clusters of ALS cases have been reported on the Pacific island of Guam and in the Kii Peninsula in Japan, which have rates 50 to 100 times higher than other parts of the world. Such clusters have also been reported in South Dakota and Italy.