Variation of therapeutic response in Parkinson's disease: a retrospective study.

A retrospective study of variations of therapeutic response (dyskinesia and on-off phenomenon) in Parkinson's disease was conducted on 278 patients treated with levodopa for at least 6 months and hospitalized at National Neurological Institute “C. Besta”of Milan between 1974 and 1984. Variations of therapeutic response (TRV) were present in 105 of 278 patients; in this group, age at illness onset was significantly lower, while duration of levodopa treatment and also duration of illness were longer than in the group of patients without TRV. Multiple logistic regression analysis showed that the most important variables were age at illness onset and duration of treatment, but they were only modestly predictive. Other factors connected with progression of disease must also contribute to the TRV.