Multiple Sclerosis (MS) is a chronic autoimmune disease where the immune system attacks the central nervous system (CNS). This attack targets the myelin sheath, the protective covering around nerve fibers in the brain and spinal cord, causing inflammation and damage. The resulting scar tissue, or sclerosis, disrupts the flow of electrical signals between the brain and the rest of the body. This neurological damage leads to symptoms including issues with movement, sensation, and cognitive function.
Impact of Multiple Sclerosis on Life Expectancy
MS is not a directly fatal disease, but it significantly increases the risk of developing life-threatening complications. Studies indicate that, on average, a person with MS has a life expectancy that is moderately reduced compared to the general population. This reduction is estimated to be between six and ten years.
The overall impact on lifespan is influenced by the severity and course of the disease. Individuals with progressive forms of MS, such as primary or secondary progressive MS, often face a greater reduction in life expectancy than those with the relapsing-remitting form. This is due to the faster accumulation of disability and complications arising from advanced physical impairment. Improved treatments and comprehensive care have worked to narrow this gap in life expectancy.
Primary Cause of Mortality in MS Patients
The most common causes of death in people with MS are complications stemming from advanced disability, rather than the neurological lesions themselves. The leading categories of death are infectious diseases and respiratory compromise. Specifically, respiratory infections like pneumonia, and systemic infections such as sepsis, are disproportionately responsible for mortality.
Studies show that the rate of death from infectious diseases in MS patients is substantially higher, sometimes more than six times greater, than in the non-MS population. Respiratory infections, particularly pneumonia, are cited as the most common immediate cause of death. Physical deterioration caused by MS progression creates an environment where common infections quickly become overwhelming and fatal.
Underlying Physiological Factors Driving Mortality Risk
The heightened mortality risk from infection and respiratory failure can be traced back to the specific neurological damage caused by the disease. One primary mechanism is the weakening of muscles involved in breathing and coughing, often caused by lesions in the brainstem and spinal cord. This muscle weakness leads to a reduced ability to clear secretions from the lungs, making individuals highly susceptible to developing pneumonia. Chronic respiratory failure is compounded in the later stages of the disease, often leading to a fatal outcome.
Swallowing difficulties, known as dysphagia, represent another significant physiological factor leading to fatal respiratory issues. Dysphagia results from lesions in the corticobulbar tracts, cerebellum, and brainstem, which control the complex process of swallowing. When swallowing is impaired, food or liquids can be accidentally inhaled into the lungs, a process called aspiration, which commonly results in aspiration pneumonia. This form of pneumonia is particularly dangerous because it introduces foreign material and bacteria directly into the lung tissue.
Bladder dysfunction is a common consequence of MS that creates a pathway for systemic infection. MS lesions frequently cause a neurogenic bladder, leading to incomplete bladder emptying and urinary stasis. This creates an ideal breeding ground for bacteria, resulting in frequent urinary tract infections (UTIs). If recurrent UTIs are not treated, the infection can ascend to the kidneys, causing pyelonephritis, and eventually spread into the bloodstream, leading to urosepsis.
Non-Disease Related Mortality Risks
Beyond the direct physiological consequences of MS progression, patients face an increased risk from causes of death not directly related to the physical disease. One concerning risk is the elevated rate of death by suicide. Living with a chronic, disabling condition, compounded by frequent depression, contributes to a much higher rate of suicide compared to the general population.
Accidental death is another heightened risk, largely due to the mobility and balance issues inherent in the disease. Due to gait disturbances, muscle weakness, and fatigue, the incidence of falls in people with MS is similar to that of adults over 80 years old. These falls can lead to serious injuries, such as hip fractures or head trauma, and the risk of a fall-related injury is approximately twice as high as in healthy individuals.
Cardiovascular disease (CVD), the leading cause of death in the general population, is also an increased risk in MS patients. This is true even when accounting for traditional risk factors like smoking or hypertension. Reduced physical activity and immobility contribute to a poorer cardiovascular profile. Chronic inflammation and a higher prevalence of depression, which is independently linked to vascular risk, further complicate the overall mortality picture.