Evidence to support early levodopa therapy in Parkinson disease.

To see whether duration of disease or of levodopa treatment was responsible for gradual worsening of parkinsonian patients, 58 persons treated with levodopa were classified into three groups based on predopa disease duration. Data over 6 years of treatment showed that disease duration was the determining factor. Patients matched for disease duration had similar disability scores regardless of duration of therapy. Matched for therapy duration, patients with longer disease duration had consistently higher disability scores. Side effects showed no differences between groups and did not increase over time. In sum, delaying therapy fails to improve disability in the early years of disease and does not confer any benefit in later years.