Muscular dystrophy is a group of inherited genetic diseases defined by progressive muscle weakness. The mortality rate and life expectancy are not a single figure but vary dramatically based on the specific type of muscular dystrophy and its severity. This variation is a result of the different ways each type affects the body’s muscles over time.
Mortality Rates by Type of Muscular Dystrophy
The outlook for individuals with muscular dystrophy is deeply connected to the specific form of the disease they have. For Duchenne muscular dystrophy (DMD), the most common and severe form, historical life expectancy was limited to the teenage years. Thanks to significant medical progress, the median survival age has steadily increased. For those born after 1990, the median life expectancy is now approximately 28 years, with some individuals living into their 30s and 40s. This improvement highlights a substantial shift in the disease’s prognosis.
Becker muscular dystrophy (BMD) is a milder form of dystrophinopathy that progresses more slowly than DMD. This slower progression means life expectancy is often longer, with many individuals living into middle or late adulthood. The average life expectancy for those with BMD is into the 40s or 50s, but the prognosis is variable, largely dependent on the severity of cardiac involvement.
Myotonic dystrophy, the most common adult-onset form, presents a wide spectrum of severity and a broad range of life expectancies. The condition is divided into two main types, DM1 and DM2. DM1 is more severe, and for those with the classic adult-onset form, life expectancy is reduced. The most severe congenital-onset form of DM1 sees a significant number of deaths before age two. Milder forms of DM1 and the less severe DM2 may not significantly impact a person’s normal lifespan.
Facioscapulohumeral muscular dystrophy (FSHD) is characterized by a slow progression of muscle weakness, starting in the face, shoulder blades, and upper arms. For a majority of individuals with FSHD, the disease does not shorten their life expectancy. While the condition can lead to significant disability, with about 20% of affected individuals eventually needing a wheelchair, its impact is rarely on the heart or respiratory systems.
Limb-girdle muscular dystrophy (LGMD) is a diverse group of more than 30 genetic disorders, which leads to a wide range of outcomes. The prognosis varies widely depending on the specific subtype, with some forms progressing rapidly and others following a slower course. For many, life expectancy can be close to normal, but in subtypes where cardiac and respiratory muscles are involved, life expectancy can be shortened.
Primary Causes of Mortality
The shortened life expectancy in certain types of muscular dystrophy is a direct result of the progressive weakening of muscles. Two systems are particularly vulnerable: the respiratory system and the cardiovascular system. The failure of these systems accounts for the majority of deaths in individuals with severe forms of the disease.
Weakness of the respiratory muscles, including the diaphragm and chest wall, is a primary cause of mortality. As these muscles deteriorate, breathing becomes increasingly difficult, leading to chronic respiratory insufficiency. This weakness also impairs the ability to cough effectively, making it difficult to clear secretions from the lungs. Consequently, individuals become highly susceptible to severe respiratory infections like pneumonia.
The heart is also a muscle and is frequently affected in many types of muscular dystrophy. The progressive muscle weakness leads to cardiomyopathy, where the heart muscle becomes weak and unable to pump blood effectively, leading to heart failure. Another serious complication is the development of arrhythmias, or irregular heartbeats, which can disrupt the heart’s normal rhythm. As respiratory care has improved, cardiac complications have become a leading cause of death.
Factors Influencing Modern Survival Rates
Significant strides in medical management have changed the course of muscular dystrophy, extending and improving quality of life. These changes are due to proactive care that addresses complications before they become life-threatening. A multidisciplinary approach involving a team of specialists is the standard of care.
Advancements in respiratory care have been a major factor in increasing survival. The use of non-invasive ventilation (NIV), often with a BiPAP machine, helps support breathing, especially during sleep. Cough-assist devices are mechanical tools that help patients clear their lungs of mucus, significantly reducing the risk of serious lung infections that were once a common cause of death.
Proactive cardiac management has also had a profound impact. Regular cardiac screening with echocardiograms allows doctors to monitor heart function closely from a young age. The early use of medications, such as ACE inhibitors and beta-blockers, is often initiated before symptoms appear. This strategy protects the heart muscle from progressive damage, delaying the onset of heart failure.
For Duchenne muscular dystrophy specifically, corticosteroid therapies are a foundational treatment. Medications like prednisone and deflazacort slow the rate of muscle degeneration. This helps preserve muscle strength, prolongs the ability to walk, and also delays the progression of both respiratory and cardiac complications.