Learn The BasicsThe prognosis of Duchenne muscular dystrophy (DMD) is generally poor, with patients affected by the disease typically needing a wheelchair for mobility by the time they are 12 years old.
As the disease progresses, respiratory and heart complications develop and are the primary cause of death in most cases. Other causes of death include aspiration, airway obstruction and pneumonia.
Survival rates
Survival rates are highly age-dependent in patients with DMD.
Mortality is very low among those up to 10 years old and increases thereafter.
According to a 2021 study, it is estimated that 86 per 1,000 patients with DMD ages 20 to 25 die each year. This number increases to 336 per 1,000 patients above age 40 each year.
Importantly, mortality rates were higher among patients born before 1970.
A total of 265 per 1,000 patients born before 1970, ages 25 to 30 died each year compared to 27.6 per 1000 patients born after 1990.
These suggest that survival rates are improving.
Life expectancy
The overall median life expectancy of patients with DMD is 22 years.
When patients are stratified by their birth date, the median life expectancy also seems to improve.
More precisely, the median life expectancy of patients born before 1970 was 18.1 years, that of those born between 1970 and 1990 was 22.9 years and that of those born after 1990 was 28.1 years.
Complications
The main complications associated with DMD are respiratory complications and cardiomyopathy, or enlargement of the heart muscle tissue.
Respiratory complications are caused by the weakness of the muscles of the ribcage and the diaphragm and can lead to difficulty coughing, pneumonia and life-threatening respiratory failure.
Cardiomyopathy can lead to irregular heartbeats, the inability of the heart to pump blood around the body and heart failure that can also be life-threatening.
Another complication of DMD is scoliosis or the sideway curvature of the spine caused by the weakness of the muscles supporting the spine having a negative effect on respiratory function.
Factors affecting prognosis
There are several factors affecting disease prognosis in DMD.
A systematic review and meta-analysis of 59 studies published on the subject found that the use of corticosteroids was associated with a delay in loss of the ability to walk in patients with DMD as well as better lung function tests, reduced need for assisted ventilation and delayed cardiomyopathy.
The analysis also found that longer treatment with corticosteroids was associated with later loss of walking ability but it also found that an early start of corticosteroid treatment may be associated with early cardiomyopathy and higher risk of fractures.
Some studies found a possible link between the type of genetic mutation and the time when the ability to walk is lost.
Patients who performed better at the six-minute walk test tended to lose the ability to walk later.
The dysfunction of the left ventricle of the heart and a forced vital capacity (the maximum amount of air that can be forcibly exhaled from the lungs after a full inhalation) of less than one liter increased the risk of heart failure and death while the use of angiotensin‐converting enzyme inhibitors reduced this risk.
Finally, fusion surgery for scoliosis had the potential to preserve lung function for longer.