ALS risk factors: who is more likely to get it

What ALS is

ALS affects motor neurons, the nerve cells in the brain and spinal cord that control voluntary muscle movement and breathing. As these neurons die, they stop sending messages to the muscles, which weaken, twitch and waste away (NINDS). ALS is progressive, meaning symptoms get worse over time (MedlinePlus).

Who is more likely to get ALS

NINDS notes that having a risk factor does not mean a person will develop ALS, and not having one does not mean they won't (NINDS). The risk factors the sources name are:

• Age. ALS can happen at any age, but symptoms most often begin between ages 55 and 75 (NINDS) (MedlinePlus).
• Sex. Men are slightly more likely than women to develop ALS, but at older ages men and women are about equally likely to be diagnosed (NINDS).
• Race and ethnicity. White people, particularly non-Hispanic White people, are most likely to develop ALS, but it affects people of all races and ethnicities (NINDS).
• Family history. Having a family member with ALS raises the risk (MedlinePlus), although NINDS says the overall risk for family members is still very low and most will not develop ALS (NINDS).
• Military service. Some studies suggest military veterans are about 1.5 to 2 times more likely to develop ALS. The reason is unclear; possible factors include exposure to lead, pesticides and other environmental toxins (NINDS).
• Head injury. Some studies have linked head injury with a higher risk of ALS, but NINDS says more research is needed to understand the connection (NINDS).

Sporadic and familial (genetic) ALS

Nearly all cases are sporadic: the disorder seems to happen at random, with no clear risk factor and no family history (NINDS). Researchers do not know what causes sporadic ALS, but it may be a combination of genetics and environmental factors (MedlinePlus).

About 10% of ALS cases are familial (also called inherited or genetic). Changes in more than a dozen genes have been found to cause familial ALS (NINDS):

• C9orf72 changes cause about 25% to 40% of familial cases, and a small share of sporadic cases.
• SOD1 changes cause another 12% to 20% of familial cases.
• SPTLC1 is linked to a rare childhood form of genetic ALS, found in 2021 by a team led by NIH, that can affect children as young as 4.

If ALS runs in your family, MedlinePlus suggests talking with your provider about whether genetic counseling and testing may be right for you (MedlinePlus).

Early symptoms

Early symptoms are often mild and may begin in one arm or leg, or in the muscles used for speaking and swallowing (MedlinePlus). NINDS lists these early symptoms (NINDS):

• muscle twitches in the arm, leg, shoulder or tongue
• muscle cramps
• tight and stiff muscles (spasticity)
• muscle weakness affecting an arm, a leg or the neck
• slurred and nasal speech
• difficulty chewing or swallowing

Over time, weakness spreads to other parts of the body (MedlinePlus). Many of these early signs, such as muscle twitches or cramps, have other, more common causes.

How ALS is diagnosed and treated

There is no single test for ALS. A doctor does a physical and neurological exam and may order tests such as electromyography (EMG), nerve conduction studies, an MRI, blood and urine tests or a spinal tap to rule out other conditions (NINDS) (MedlinePlus). NINDS says treatments may work best soon after symptoms start, and a neurologist familiar with ALS can help with an early diagnosis (NINDS).

There is no treatment that reverses the damage or cures ALS at this time. FDA-approved medicines may slow progression, help manage symptoms or extend survival, and a team of professionals, including physical, occupational, speech and respiratory therapists, can help people stay mobile and independent for as long as possible (NINDS).

Common questions

Is ALS genetic?

Usually not. About 10% of cases are familial, and the rest are sporadic, with no family history (NINDS). A family member with ALS raises your risk, but most relatives of people with ALS never develop it (NINDS) (MedlinePlus).

Can ALS be prevented?

MedlinePlus says there is no known way to prevent ALS (MedlinePlus). The main risk factors the sources name, such as age, sex, race and family history, cannot be changed.

Does ALS affect thinking and memory?

Most people with ALS can still reason, remember and understand, but some have changes in language, thinking or behavior, and some develop a form of frontotemporal dementia (FTD-ALS) (MedlinePlus) (NINDS). See dementia risk factors.

How is ALS different from Parkinson's disease?

Both are nervous system disorders that get worse over time. ALS damages the motor neurons that carry messages to the muscles, which leads to weakness and muscle wasting (NINDS). For Parkinson's, see Parkinson's disease risk factors.

Is there an ALS risk calculator?

No. The sources on this page do not offer a validated score for the general public, so we do not provide one.

Also see multiple sclerosis risk factors.