Multiple Sclerosis (MS) is a chronic disease that affects the central nervous system (brain and spinal cord). It is characterized by the immune system mistakenly attacking the protective layer around nerve fibers, a process called demyelination, which disrupts communication throughout the body. Diagnosis of MS can occur in a person’s 70s, although it is an exceptionally rare occurrence. This late diagnosis falls into a distinct category of the disease and presents unique challenges for both patients and physicians.
The Standard Age Range for MS
Multiple Sclerosis is primarily a disease of young adulthood, with the majority of diagnoses occurring between the ages of 20 and 50 years. The average age of onset is around 34 years old. This typical age range is why MS is the most common cause of non-traumatic neurological disability in this population.
The prevalence of MS generally peaks in the age groups between 55 and 65 years, but this reflects people who were diagnosed years earlier living longer with the condition. The disease affects women more often than men, with an estimated three-to-one ratio in adult-onset cases. An onset outside of the 20 to 50 age window is unusual.
Late-Onset Multiple Sclerosis
The diagnosis of MS after the age of 50 is formally defined as Late-Onset Multiple Sclerosis (LOMS). While LOMS itself is uncommon, accounting for approximately 5 to 10% of all MS cases, diagnosis in the 70s is considered very late-onset MS (VLOMS) and is exceedingly rare. Diagnosis after age 60 accounts for only about 1% of total MS cases.
The average age of symptom onset for LOMS ranges between 53 and 67 years. The increasing incidence of LOMS in recent years is partly attributed to improved diagnostic tools and greater awareness, which may be capturing cases that were previously missed or misdiagnosed.
Distinguishing MS from Other Conditions
The process of diagnosing MS in a person in their 70s is complex, primarily due to the need for a rigorous differential diagnosis. Neurological symptoms in older adults can be caused by various other age-related conditions that closely mimic the presentation of MS. These conditions must be definitively ruled out before a diagnosis of MS can be confirmed.
Symptoms like balance issues, gait disturbance, and cognitive changes can be mistakenly attributed to the normal aging process, or to conditions like small vessel ischemic disease, which involves changes in the brain’s blood vessels. Stroke sequelae, B12 deficiency, and other causes of myelopathy, such as cervical myopathy, also need to be excluded.
Physicians must rigorously apply the McDonald criteria, the international standards for MS diagnosis, which often requires extensive testing such as magnetic resonance imaging (MRI) scans and spinal fluid analysis. The challenge is that MRI findings in older adults, such as white matter lesions, can be caused by common vascular changes, making it difficult to distinguish them from MS-specific lesions.
Disease Course When Onset is Late
When MS is diagnosed in later life, the disease course and prognosis tend to be different compared to those diagnosed in young adulthood. Late-onset MS is more likely to present as Primary Progressive MS (PPMS), a form characterized by a steady, gradual worsening of neurological function from the beginning, without distinct relapses and remissions.
The progressive nature of LOMS often leads to a more rapid accumulation of disability, with physical milestones such as needing a cane or wheelchair reached in a shorter time frame than in younger-onset patients. Motor deficits, including muscle weakness, severe balance issues, and significant gait disturbance, are often the most prominent and disabling initial symptoms.
Sensory changes and visual problems, which are common initial symptoms in younger adults, are less frequently reported at the onset of LOMS. Treatment considerations are also more complicated in older patients, given the potential for existing comorbidities and the need to carefully manage potential drug interactions with disease-modifying therapies.