Response fluctuations in Parkinson's disease.

We studied the influence of several factors on the occurrence of response fluctuations in 91 Parkinson's disease patients. These included the age at onset, the presenting symptom, the duration of illness, and the stage of the disease at the time of initiation of levodopa treatment as time-independent covariates, and the mean and last dosage of levodopa as time-dependent covariates. Taken separately, none of the factors was related to the occurrence of response fluctuations. We found no evidence to delay levodopa treatment to a later stage of the disease. In the analysis of the combined influence of the age at onset and the interval before levodopa treatment, we noted a tendency for response fluctuations to occur less frequently in those patients with age at onset of 60 years and over who had started levodopa treatment more than 2 years after the 1st symptom. Our analysis of the combination of time-dependent factors suggests that response fluctuations are a likely event in those patients in whom the course of the disease recently necessitated an increase in the dosage of levodopa.