Comparisons
Part 5

A comparison of HD to Alzheimer's and Parkinson's diseases

Prognosis

As discussed elsewhere in this website, HD is a progressively debilitating disease with no known cure. The person with Huntington’s disease may be able to maintain a job for several years after diagnosis, despite the increase in disability. Loss of cognitive functions and increase in motor and behavioral symptoms eventually prevent the person with HD from continuing employment. Ultimately, severe motor symptoms prevent mobility. HD is usually fatal within15 to 20 years. Progressive weakness of respiratory and swallowing muscles leads to increased respiratory infection and choking, the most common causes of death. (For more information about the complications of HD, click here.) However, not all patients with Huntington’s disease progress at the same pace and are equally affected. The number of repeats may determine severity. There are people with a low number of repeats that have mild abnormal movements later in life and progression is slow whereas others with a large repeat length who are severely affected at a young age.

Although different in many ways, Alzheimer’s disease is also an incurable and progressively debilitating disease that can vary widely in its progression. Some people have a very precipitous course and go downhill rapidly, while others remain stable for a long time. For some, the disease only for the last 5 years of life; others may have it for as many as 20 years. A study of the prognosis of AD at the University of Massachusetts Medical School suggests that initial degree of severity (“how far”) rather than the variation in the rate of progression (“how fast”) best predicts prognosis in the early to intermediate stages of Alzheimer’s disease. Total disability is common in people with Alzheimers, and the most common cause of death is infection or a failure of other body systems.

Predicting disease progression for Parkinson’s disease is difficult because of the wide spectrum of disease types. Again, the course and prognosis of this disease vary according to the individual. Without treatment, PD causes severe disability or death in 25% of patients within 5 years, 65% of survivors after 10 years, and 89% of survivors after 15 years. However, with treatment, the life expectancy of people with PD without an accompanying dementia is nearly normal. The mean time from diagnosis to death in treated PD is 14 years. Death is usually due to complications of immobility, such as pulmonary embolism (blood clot in the lungs) or aspiration pneumonia (lung infection from regurgitated stomach contents).

Last Modified: 5-20-04

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