ALS Age of Onset, Risk Factors, and Early Signs

With amyotrophic lateral sclerosis (ALS), your voluntary muscles may begin to cause you problems. The early signs may be so minor you may overlook them. The age of onset for ALS is most often between 55 and 75.

Initial signs of ALS can vary from muscle twitches or stiffness to difficulty swallowing. But this is a progressive neurological disease that ultimately makes movement impossible. It is also known as Lou Gehrig’s disease.

ALS Age of Onset

ALS can occur at any age, but it most commonly affects individuals between 55 and 75. A genetic form of ALS, caused by the SPTLC1 gene, can affect children as young as 4. This gene impacts the body’s fat production.

Early Signs and Symptoms of ALS

Early symptoms of ALS can be subtle and easy to overlook. These may include:

• Muscle cramps
• Muscle stiffness or tightness
• Muscle twitching or contractions
• Difficulty chewing or swallowing
• Ongoing difficulty speaking clearly, such as unexpected slurring of words

You may suddenly have trouble buttoning your coat or signing your name. Problems can start in different parts of the body.

Bulbar onset is a type of ALS that causes problems with swallowing or speech. Frequently tripping or running awkwardly are signs of limb onset ALS.

Causes and Risk Factors

Unfortunately, most of the time, ALS occurs spontaneously without any apparent links to family history or genetic factors to explain it. This is called sporadic ALS.

In about 10% of ALS cases, a family history is present. For familial ALS, each child has a 50% chance of inheriting the gene mutation that could cause the disease.

People who served in the military are somewhat more likely to develop ALS than those who haven’t served. The Department of Veterans Affairs recognizes ALS as a service-related condition.

This may be due to the exposure to toxins released during warfare, environmental factors, or continually participating in highly strenuous activities. The latter may explain why professional athletes like National Football League players may be predisposed to this condition. ALS is commonly called Lou Gehrig’s disease after the professional baseball player.

Genetics

Genetics may play a role in ALS. In about two-thirds of cases in which ALS runs in families, a gene mutation can be identified. In fact, more than 25 genes may contribute to ALS.

Some of the key genes that may be implicated include the following:

• The SOD1 gene mutation was the first detected (in 1993). It is thought to account for up to 20% of familial ALS cases and up to 2% of cases of sporadic ALS. Only one copy of the gene (from one parent) is enough to cause ALS when inherited. While the exact mechanism remains unclear, researchers think that the mutation causes the protein it produces to form clumps in motor neurons and astrocytes, leading to the death of these cells and ALS.
• C9orf72, first discovered in 2011, is the most common genetic source of ALS, responsible for up to 40% of ALS cases that run in families and 7% of sporadic ones (cases that occur without a family history). Just one copy of the gene is needed to cause ALS.
• NEK1 is a genetic mutation that accounts for 3% of all ALS cases. This is present in both instances that run in families as well as those that occur spontaneously.
• TDP43 is found in 4% of familial cases and 1% of sporadic ones. Mutations in the TDP43 gene can cause the protein it produces to clump in motor neurons.
• FUS (fused in sarcoma) was discovered in 2008. Just one copy of this dominant gene is needed to cause ALS. This causes 5% of familial cases and 1% of sporadic ones. This resembles TDP43, and likely plays a similar role in causing ALS.
• KIF5A (kinesin family member 5A) was first detected in 2018. Just one copy of this gene is needed to cause ALS. Those with this mutation tend to survive longer than others with ALS, living on average for about 10 years after diagnosis.

Demographic Factors

ALS can affect anyone, but some groups have a higher risk, such as:

• White males over 60 without a family history of ALS
• In the United States, Black individuals are less frequently diagnosed than White individuals
• Approximately 5% to 10% of patients with ALS have a family history of the condition

Higher concentrations of ALS appear in the U.S. Midwest and Northeast, areas where there is a high proportion of Whites. The Western region of the United States has the lowest proportion of ALS cases, possibly due to the diversity of the population.

The slightly higher proportion of men vs. women wanes as people age.

Note that Verywell Health prefers to use inclusive terminology. But when citing health authorities and research, the terms relating to gender and sex from those sources are used.

Environmental Triggers

The environment that you live in also plays an important role. Here are some factors that are suspected to potentially trigger ALS:

• Smoking
• Beta-methylamino-l-alanine (BMAA), a naturally produced neurotoxin
• Exposure to metals, radiation, solvents, and other toxins
• Pesticides
• Viruses (but none yet identified)
• Military service
• Intense exercise as part of your occupation

How ALS Progresses

ALS may start with minor issues such as difficulty fastening buttons or turning on the ignition in your car. This may seem perplexing at first. As the disease worsens, so do problems such as speaking, swallowing, moving, or breathing.

With time, weight loss may also become a problem. This occurs because those with ALS tend to burn calories more rapidly and they may also have difficulty eating.

ALS mainly affects physical functions. Most people with ALS maintain their reasoning abilities and understanding of how the condition affects them. A small percentage of people with ALS may also have difficulties with language or making decisions.

When to Seek Care

No test can quickly identify whether you have ALS. It takes nine months to two years for most people to be diagnosed with the condition. That’s because it’s easy to write off early mishaps as a product of aging.

Consult your healthcare provider as soon as you notice any signs of ALS. If your healthcare provider suspects ALS, they will likely refer you to a neurologist (a specialist in conditions affecting the central nervous system comprising the brain and spinal cord).