What is ALS?

ALS is a progressive nervous system disease that affects nerve cells in the brain and spinal cord, causing the cells to deteriorate and eventually die.

The disease specifically affects motor neurons, which control muscles that govern voluntary movements. When motor neurons die, the brain is no longer able to activate those muscles.

This can cause specific muscles to become weak and leads to paralysis. As a result, people may lose the ability to move, eat, speak and breathe.

In 2017, there were an estimated 18,000 to 32,000 cases of ALS in the United States, according to the Centers for Disease Control and Prevention.

How does ALS affect people?

The most common initial symptom of ALS is muscle weakness — which is usually painless.

Dr. Stephen Goutman, director of the Pranger ALS Clinic and associate director of the ALS Center of Excellence at Michigan Medicine in Ann Arbor, said muscle weakness typically starts in one region of the body and then spreads to other areas.

Symptoms of ALS generally start gradually, but can vary among people, depending on which motor neurons are affected. Symptoms include:

• weakness or fatigue in the legs, feet, arms or hands
• tripping and falling
• dropping objects or other hand clumsiness
• muscle cramps or twitches
• slurred speech
• swallowing difficulty
• uncontrollable crying or laughing

Goutman said ALS doesn’t just affect the motor neurons. Many people with the disease also experience cognitive changes such as decision-making difficulties, personality changes or irritability.

Due to the degeneration of the motor neurons, ALS eventually affects chewing, swallowing, speaking, and breathing.

“Because of the progressive nature of the disease, it is unfortunately fatal, mostly because of the difficulties with breathing,” said Goutman.

On average, people with ALS live from 3 to 5 years after they develop symptoms, although some people live longer.

ALS doesn’t usually affect bladder control, vision or other senses because these are controlled by different types of neurons.

Who is most at risk from ALS?

Certain factors increase the risk of developing ALS, including:

• Heredity. About 5-10% of ALS cases occur within families and are caused by genes known to be linked to ALS.
• Age. ALS typically occurs in people between 55 and 75 years of age, although cases can occur in younger people.
• Sex. Men have a slightly higher risk than women of developing ALS. Familial ALS occurs equally often in men and women.
• Genetics. Some studies suggest that 60% of the risk of non-inherited ALS is due to genetic factors. People who have these gene variations may be more likely to develop ALS.

In addition, research has found a possible link between ALS and certain environmental factors. More research is needed to fully understand these connections.

• Smoking. Some studies indicate that smokers have a higher risk of developing ALS than people who never smoked.
• Environmental exposures. Research suggests a possible link between ALS risk and exposure to heavy metals (such as lead and mercury), chemical solvents, radiation, pesticides and other toxins.
• Military service. Studies indicate that people who served in the military have a higher risk of developing ALS compared to those who did not serve in the military.
• Occupation. Research suggests that the ALS risk is higher among people with certain jobs, such as construction, manufacturing, mechanical or painting.
• Contact sports. Studies have found a higher risk of ALS among people who play competitive contact sports that involve repetitive head and neck trauma, such as hockey, football and soccer.