Effects of dopaminergic medication on executive function in drug-naive patients with Parkinson’s disease: using behavioral assessment of the dysexecutive syndrome

Abstract

Background: There is a correlation between executive and motor functions in Parkinson’s disease (PD). However, the effect of dopaminergic medication on executive function in PD patients is uncertain, especially in drug-naive de novo PD patients. The Behavioral Assessment of the Dysexecutive Syndrome (BADS) is a sensitive executive assessment tool. Objective: We examined the effect of dopaminergic medication on executive function in drug-naive PD patients with approval by the Showa University ethics committee. Methods: Dopaminergic drugs (levodopa, dopamine agonists, selegiline) were given to 17 (9 males, 8 females) drug-naive PD patients without dementia (Mini-Mental State Examination score above 25) and increased to the optimal dose to obtain improvement in motor symptoms. Patients were tested prior to and at 4 to 7 months after drug initiation. Motor function was assessed using the Unified Parkinson’s Disease Rating Scale (UPDRS: total score and subscores of tremor, rigidity, bradykinesia and gait). Executive function was assessed using the Japanese version of the BADS. Improvements from baseline for both motor and executive assessments were compared with the levodopa equivalent dose (LED). Results: Dopaminergic drugs significantly ameliorated all motor problems. The improvement did not correlate with the LED. The mean BADS score showed no significant improvement. However, improvement in the BADS score showed a significant positive correlation with the LED. Conclusions: The effects of dopaminergic medication on executive function in drug-naïve PD patients are dose dependent.