ALS vs. MS: Similarities and Differences

Multiple sclerosis (MS) and amyotrophic lateral sclerosis (ALS, also called Lou Gehrig’s disease) are both diseases that affect your central nervous system. While they have some overlapping symptoms, like muscle stiffness and loss of balance, they may be more different than alike.

ALS destroys the specific parts of your brain and spinal cord responsible for voluntary muscle movements, like walking, eating, and talking. MS damages the protective coverings around the nerves of your brain, spinal cord, and eyes, and may cause a broader range of symptoms.

ALS and multiple sclerosis both attack the nervous system, but the damage ALS causes is more targeted, mainly affecting physical movement. People with MS often have more varied symptoms, such as vision changes, cognitive changes, and bladder problems.

Despite having similar symptoms, MS and ALS are very different diseases—here’s why.

They Attack Different Parts of the Nervous System

MS damages many nerve cells and their myelin, the protective covering that surrounds these nerves. The attack on myelin can cause scar tissue or lesions, which interfere with proper nerve signaling and function.

ALS also causes nerve damage, but only to a type of nerve called motor neurons. Motor neurons control voluntary movements by sending messages to your muscles. ALS kills off motor neurons, so your brain can’t send messages to your muscles anymore. The muscles weaken and eventually waste away. 

They Have Different Causes

MS and ALS are not in the same disease category. ALS is a neurodegenerative disease, a condition where your body’s nervous system cells weaken and die over time. MS is likely an autoimmune disease, a condition where your immune system mistakenly attacks healthy cells.

MS Is More Prevalent 

In the United States, multiple sclerosis is more common than ALS. In 2022, the number of people with ALS was estimated to be around 33,000. In 2020, more than 900,000 people had MS.

They Affect Different Demographics

ALS and MS are more common in certain people depending on their biological sex and age. 

• Sex: MS is more common in women—about 75% of people with the disease are female. ALS is 20% more common among younger men than younger women, but there is a less noticeable difference among people of older age.
• Age: Most people are diagnosed with MS between the ages of 20 and 40.ALS is more commonly diagnosed between the ages of 55 and 75.

ALS Has a Shorter Life Expectancy 

ALS is fatal, with a life expectancy of three to five years after diagnosis, but many factors may influence your lifespan, including your age and how quickly your illness progresses. About 10% of people with ALS live for 10 years after diagnosis, and 5% live for 20 years or more.

The average life expectancy for a person with multiple sclerosis is 30-35 years after diagnosis. MS itself isn’t fatal, but complications of the disease may affect how long you live. For some people, MS doesn’t shorten their lifespan at all. For others, it lowers it by around seven years. 

Although ALS and MS are different diseases, they both affect the nervous system and have several things in common.

They Are Difficult To Diagnose

People with MS and ALS often wait a long time for an accurate diagnosis. Both conditions are complex, and the symptoms often overlap with those of other nervous system disorders.

There is no single test for either condition. Doctors rely on a combination of blood work, physical exams, and diagnostic tests like spinal fluid testing and magnetic resonance imaging (MRI) to rule out other causes and find evidence of MS or ALS. 

On average, it takes about 18 months to be diagnosed with MS and 10-16 months for an ALS diagnosis after symptoms appear.

Smoking Is a Risk Factor for Both    

Smoking increases your risk for MS, speeds up the progression of the disease, and makes symptoms worse. The role of smoking in ALS is somewhat less clear, but current smoking is a risk factor for many people, especially older women.

There’s No Cure for Either 

There is no way to cure MS or ALS, but there are treatment options for both conditions that can help you manage your symptoms and slow down disease progression.

For ALS, getting treatment means you may be able to extend your life expectancy and live with less disability for longer.

For MS, treatment may lead to fewer or milder symptoms, fewer flares, and fewer complications as your illness progresses.

It’s possible but extremely rare to have both ALS and MS. There are only a few documented cases of people who have both.

It’s important to contact a healthcare provider if you have any noticeable changes to your neurological health, especially if any of those changes are typical symptoms of MS or ALS. Make an appointment if your symptoms are new, persistent, or worsening.

A primary care provider may be able to identify or rule out more common causes. If your primary care provider thinks you need further evaluation, they may refer you to a neurologist, a doctor who treats disorders of the nervous system such as MS and ALS.

ALS and MS are both disorders of the nervous system that damage nerve cells and cause mobility difficulties. MS is more common, and both conditions affect people at different stages of adulthood.

Though there is no cure for either, MS can be managed. ALS is ultimately fatal, making it important to understand the differences between the two disorders and get the right diagnosis as soon as possible.