Multiple Sclerosis (MS) is a chronic disease of the central nervous system where the immune system mistakenly attacks the protective myelin sheath surrounding nerve fibers in the brain and spinal cord. This damage disrupts communication between the brain and the rest of the body, leading to a wide array of unpredictable symptoms. While MS is a chronic condition that generally leads to accumulating disability over time, the rate and manner of progression vary significantly between individuals. Age is one of the strongest factors influencing how MS progresses, often correlating with a shift in the underlying disease process.
Tracking Disease Progression Over Time
The long-term course of Multiple Sclerosis is understood by distinguishing between two types of activity: relapses and progression. Relapses, or flares, are episodes of new or suddenly worsening neurological symptoms, typically followed by partial or full recovery. These relapses are considered “disease activity” and are often linked to new inflammatory lesions visible on an MRI scan.
Progression refers to the slow, cumulative accumulation of irreversible disability that occurs over many years, independent of acute relapses. This gradual worsening is often measured using the Expanded Disability Status Scale (EDSS), which assesses functional systems, focusing heavily on walking ability. Progression is thought to be driven by neurodegeneration, or the slow loss of nerve cells, which continues even as inflammatory disease activity slows down. This accumulation of damage is often what leads people to feel their disease is steadily worsening over time.
How Different MS Types Affect the Long-Term Course
The way MS progresses is highly dependent on the disease course initially diagnosed. The majority of people are first diagnosed with Relapsing-Remitting MS (RRMS), characterized by distinct relapses followed by periods of remission. Over time, many people with RRMS transition to Secondary Progressive MS (SPMS), which is a major driver of perceived “worsening with age.”
The transition to SPMS typically occurs between 10 and 25 years after the initial diagnosis, often when a person is in their 40s or 50s. SPMS is characterized by the gradual worsening and accumulation of neurological symptoms and disability, with or without occasional relapses. The underlying mechanism shifts from primarily inflammatory attacks to one dominated by neurodegeneration and chronic, low-level inflammation within the central nervous system. Improved use of disease-modifying therapies (DMTs) has helped reduce the frequency of this transition in recent years.
A smaller group of people is diagnosed with Primary Progressive MS (PPMS), characterized by a steady, gradual worsening of neurological function from the onset. Unlike RRMS and SPMS, PPMS does not include initial relapses and remissions, though the rate of progression is variable. PPMS is often diagnosed later, with the average age of onset being about 10 years older than that of relapsing forms. This form of MS tends to involve more difficulty with walking and fewer inflammatory lesions in the brain, making the gradual accumulation of disability its defining characteristic.
The Impact of Normal Aging on Existing Symptoms
The physical decline associated with normal aging can compound the effects of existing MS damage. As people age, their brain’s ability to compensate for nerve damage, known as neurological reserve, naturally diminishes. This reduction in reserve capacity means that pre-existing MS lesions become more symptomatic, making old damage feel more noticeable or severe.
Age-related changes in the immune system, often called immunosenescence, also play a role in MS progression. While this process can lead to fewer acute relapses, it is associated with chronic, low-grade inflammation that contributes to neurodegeneration. Furthermore, the risk of developing other health conditions, or comorbidities, increases significantly with age, and these can directly exacerbate MS symptoms. Conditions such as arthritis, cardiovascular issues, or diabetes can worsen fatigue, mobility problems, and pain, making it difficult to determine whether a change in function is due to MS progression or the effects of aging and other illnesses.
Strategies for Managing Long-Term MS
Managing MS over the long term requires a comprehensive approach that targets both the disease and the effects of aging. Adherence to prescribed disease-modifying therapies (DMTs) is important, as these treatments reduce disease activity and slow the accumulation of disability. For older patients, treatment decisions involve balancing the benefit of DMTs with the increased risk of infections and side effects from an aging immune system.
Symptom management is equally important and is often addressed through rehabilitation therapies. Physical therapy and occupational therapy are used to maintain muscle strength, improve balance, and adapt to functional changes, helping to maximize physical reserve. Lifestyle factors also contribute to long-term well-being, including regular exercise, a healthy diet, and stress management, which help counteract the effects of age-related decline and comorbidities.