The effect of stage of Parkinson's disease at the onset of levodopa therapy on development of motor complications

The aim of this study was to ascertain whether the stage of Parkinson's disease (PD) (according to the Hoehn and Yahr staging system) would affect the length of time between the introduction of levodopa therapy and appearance of levodopa-associated motor complications. Forty patients with clinically definite PD were studied. In all, clinical and therapeutic data were collected from the time of diagnosis to the time of levodopa-associated motor complications (i.e. dyskinesia, motor fluctuations). In 17 patients, levodopa could be started in Hoehn and Yahr stage I (HY-I; 16.2 months after the onset of PD), whilst in 13 patients levodopa could be started in H&Y-II (19.6 months after the onset of the disease) and in 10 in H&Y-III (45.1 months after the onset of PD). Cox proportional hazard regression model shows that the PD patients in whom the initial levodopa treatment was introduced at stage III develop both dyskinesias and motor fluctuations significantly earlier than the patients whose levodopa started in stage I and II of PD. The median interval to develop dyskinesias was 66, 72 and 24 months for patients in whom levodopa was introduced in stage 1, II and III, respectively. These values were 64, 55 and 14 months for motor fluctuations. These findings add to the clinical arguments that favour an essential role of severity of PD at levodopa initiation as a risk factor for the development of levodopa-associated motor complications.