Why Thinking Speed Slows in MS: Age of Onset Matters

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Key Takeaway

Thinking speed problems in MS come from different brain changes depending on whether the disease started before or after age 45.

What They Found

The study looked at people whose MS started before age 45 (adult-onset) and at or after 45 (late-onset) and tested thinking speed using the Symbol Digit Modalities Test (SDMT). About the same share of both groups had slowed thinking (around 38–39%), so the amount of difficulty was similar. In adult-onset MS, problems on the thinking test were linked mostly to breaks in the brain's communication network (like damaged phone lines inside one half of the brain). In late-onset MS, thinking problems were tied more to brain tissue loss (gray matter atrophy) and damage to connections between the two halves of the brain (like a weakened bridge between two neighborhoods). Overall, younger-start MS had network wiring problems as the main issue, while older-start MS showed more tissue loss and loss of cross-brain connections as the main issue.

Who Should Care and Why

People with MS and their caregivers should care because the reason for slowed thinking can be different depending on when MS began; this can change which strategies might help. For someone whose MS began younger, therapies or exercises that aim to improve brain network efficiency (like cognitive training or maintaining social and mental activity) might be most useful — like tuning up a radio so stations come in clearer. For someone whose MS began later, protecting brain tissue and general brain health (healthy lifestyle, close monitoring, and treatments that slow tissue loss) may be more important — like preventing erosion of a bridge rather than just fixing the wiring under it. Doctors and therapists can use this information to tailor monitoring and care plans — for example, choosing different tests or imaging to track the likely problems. Caregivers can focus support on the practical side: cognitive training and daily routines that keep the brain engaged for younger-onset, and activities supporting overall brain health and safety for later-onset.

Important Considerations

This study looked at people within six years of MS symptom start, so findings may not apply the same way after many more years of disease. The research shows associations (things that go together) but does not prove one thing causes the other, so treatments should be discussed with your doctor. Imaging measures can be complex and are not always available everywhere, so check with your care team about what tests make sense for you.

Categories:

Specific Symptoms MS Diagnostics MS Progression

Article Topics:

Multiple sclerosiscognitive impairmentlate-onset multiple sclerosisstructural connectivity

Whether you’ve recently been diagnosed with Multiple Sclerosis (MS) or are seeking to broaden your understanding of this complex, neurodegenerative disease, navigating the latest research can feel overwhelming. Studies published in respected medical journals like Multiple sclerosis (Houndmills, Basingstoke, England) often range from early-stage, exploratory work to advanced clinical trials. These evidence-based findings help shape new disease-modifying therapies, guide symptom management techniques, and deepen our knowledge of MS progression.

However, not all research is created equal. Some clinical research studies may have smaller sample sizes, evolving methodologies, or limitations that warrant careful interpretation. For a more comprehensive, accurate understanding, we recommend reviewing the original source material—accessible via the More Details section above—and consulting with healthcare professionals who specialize in MS care.

By presenting a wide range of MS-focused studies—spanning cutting-edge treatments, emerging therapies, and established best practices—we aim to empower patients, caregivers, and clinicians to stay informed and make well-informed decisions when managing Multiple Sclerosis.

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