Progression and survival in Parkinson's disease

Parkinson's disease is a progressive disorder and no permanent cure has ever been documented. The clinical onset, which usually occurs at an age of 55-65 years, is probably preceded by a preclinical period of two or more decades. The progression rate of the disease is extremely variable in different patients; in individual patients on the other hand, the progression of motor symptoms is fairly constant. The tremor-dominant type of the disease usually has a more favourable prognosis than the hypokinetic type. Onset at an older age may be associated with a faster progression rate and the development of cognitive failure. In natural conditions, the average duration of Parkinson's disease is 10 years, although with a considerable range. The disease shortens life expectancy, which can be restored at least partially by treating patients with levodopa and other modern drugs. The highest benefit in increasing life expectancy is obtained when the treatment is initiated at a relatively early stage of the disease.