The Rate of Cognitive Decline in Parkinson Disease

Objectives: To measure the rate and predictors of change on the Mini-Mental State Examination in patients with Parkinson disease (PD) and to compare that change with the Mini-Mental State Examination changes of patients with Alzheimer disease and nondemented subjects.

Patients: Patients with PD were drawn from a community-based cohort in Rogaland County, Norway. Those who were without cognitive impairment at disease onset and participated in 1 or more assessments after visit 1 were included and examined after 4 years (visit 2) and 8 years (visit 3). Motor, cognitive, and psychiatric symptoms were rated using standardized scales at visit 1. Two population-based cohorts of patients with Alzheimer disease and nondemented control subjects were included for comparison. Data were analyzed using a mixed-effects model.

Results: One hundred twenty-nine PD patients (57% women) were included. The mean (SD) Mini-Mental State Examination score at visit 1 was 27.3 (5.7). The mean annual decline in score from visit 1 to visit 3 was 1.1 (95% confidence interval, 0.8 to 1.3; 3.9% change from visit 1). Patients with PD and dementia (n = 49) had an annual decline from visit 1 to visit 2 of 2.3 (95% confidence interval, 2.1 to 2.5; 9.1% change from visit 1), compared with 2.6 (95% confidence interval, 2.3 to 2.8; 10.6% change from visit 1) in the patients with Alzheimer disease (n = 34) (mean annual decline among patients with PD and dementia vs patients with Alzheimer disease, not significant). The change in score for nondemented PD patients (n = 80) was small and similar to that for nondemented control subjects (n = 1621). Old age, hallucinations, and more severe motor symptoms (rigidity and motor scores mediated by nondopaminergic lesions) at visit 1 were significantly associated with a more rapid cognitive decline in patients with PD.

Conclusions: The mean annual decline on the Mini-Mental State Examination for PD patients was 1 point. However, a marked variation was found. In patients with PD and dementia, the mean annual decline was 2.3, which was similar to the decline observed in patients with Alzheimer disease.