The effect of symptom duration on cognitive and motor performance in parkinsonism.

Neuropsychologic test performance was examined in a normal control group and in three groups of Parkinson disease patients, with symptoms for 2 years or less, for 3 to 5 years, or for 6 to 15 years. On a test battery sampling a wide variety of cognitive and motor abilities, significant intergroup differences occurred primarily on tasks with a primary motor component, although mild intergroup cognitive impairment was also demonstrated. The results suggested that maximal deterioration occurred during the first 5 years of symptoms, with few significant additional changes after that.