Late-Onset Multiple Sclerosis

Uncommon Form of MS Linked to Poor Outcomes

Late-onset multiple sclerosis (MS) is commonly defined as the occurrence of the first symptoms after age 50. The way the disease manifests can be far different from what one would expect with adult-onset MS, the most common form affecting people in their mid-20s and 30s.

Understanding Multiple Sclerosis

MS is a chronic disease of the central nervous system (CNS), which includes your brain, spinal cord, and optic (eye) nerves. In MS, your immune system attacks nerve cells and the fatty myelin sheath surrounding them, causing scarring.

The myelin scar tissue “jams” communication between your brain and your body. The resulting distortion and blocking of messages between the brain and spinal cord lead to the symptoms and disability that we recognize with MS.

It’s not yet known what “turns on” the immune system response in a person with MS. However, this appears to occur in people with an inherited (genetic) susceptibility to the disease who are exposed to one or more environmental triggers, including smoking, stress, and vitamin D deficiency.

Diagnostic Challenges

People over the age of 50 are diagnosed with MS in about 3 percent to 4 percent of cases, according to a study in Multiple Sclerosis and Related Disorders. Unfortunately, MS may be harder to diagnose in people over 50 for a variety of reasons.

One of the main barriers is that MS has not been studied in the older adult population as much as in younger adults. This is important because the disease may vary between younger and older people, including the range of symptoms experienced.

Because of this, late-onset MS is often missed by doctors who are more familiar with the disease in younger adults.

Symptoms of late-onset MS are often mistaken for signs of normal aging. These include fatigue, balance problems, vision changes, and cognitive impairment that doctors may presume are aging-related.

Even some diagnostic tests may be incorrectly interpreted if steps are not taken to explore immune-mediated diseases. For example, magnetic resonance imaging (MRI) commonly used to diagnose MS may show the white-matter brain damage consistent with MS but be interpreted as damage caused by any one of several vascular diseases common in older people.

In late-onset MS, symptoms can easily mimic those of other disorders including:

Delayed diagnosis and treatment are among the main reasons why people with late-onset MS tend to fare worse.

Late-Onset Disease Progression

While the initial symptoms of late-onset MS develop later in life, research suggests that physical disability and loss of motor function occur faster and more frequently.

Studies have shown that motor impairment is far more common in people with late-onset MS. Moreover, older adults tended to have more severe progressive forms of MS compared to younger adults who usually had relapsing-remitting MS.

On the other hand, optic neuritis, and dysarthria (speech problems) were more common in younger people. The onset of sensory symptoms, ataxia, cognitive function, and fatigue did not differ between the two age groups. 

In terms of radiological findings, spinal cord lesions were more common in people with late-onset MS, and lesions in the cerebellum were more common in people with younger-onset MS. Because of delays in diagnosis, age, concurrent illness, and other factors, late-onset MS portend to poorer outcomes.

A 2016 study published in the journal PLoS One concluded that people with late-onset MS reached a higher disability level faster—a median time of 6.5 years—compared to a median of 12.8 years for people with adult-onset MS.

A Word From Verywell

In the end, the course of late-onset MS and how different it is from young-onset MS is still not entirely clear. 

That being said, a prompt and accurate diagnosis is as critically important in late-onset MS as it is at any age. This is because promptly starting treatment with disease-modifying medications can reduce MS attacks and new lesions, as well as slow the progression of the disease. 

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