Long-term responses of Parkinson's disease to levodopa therapy.

The long-term responses of Parkinson's disease to levodopa therapy were studied in the patient material followed-up for 9 years. Levodopa treatment alleviated the parkinsonian symptoms to a considerable degree and substantially improved the quality of life of the parkinsonian patients. However, after treatment for 2 to 3 years, a progressive deterioration of parkinsonian symptoms was observed accompanied by an increase in the incidence of dyskinesias, on-off phenomena, postural instability and dementia. An analysis of the mortality rates in the follow-up material of 349 patients showed that initially levodopa treatment decreased the excess mortality due to Parkinson's disease. The ratios of observed to expected deaths ranged from 1.10 to 1.67. However, during the ninth year of treatment the ratio increased to 1.95 almost reaching the values obtained in the first years of levodopa treatment. Thus it appears that levodopa has only a limited period of usefulness in the treatment of Parkinson's disease. Although levodopa very significantly improves parkinsonian symptoms, it does not arrest the pathological progress and modify the natural course of the disease.