The average annual decline in cognitive function is similar in patients with Parkinson disease and dementia and patients with Alzheimer disease, according to an article in the December issue of The Archives of Neurology.

According to information in the article, dementia is common in patients with Parkinson disease and is associated with rapid motor and functional decline, higher death rates, and increased caregiver stress. However, few studies have focused on the rate of cognitive decline in Parkinson Disease, and the results vary considerably.

Dag Aarsland, MD, PhD, and his Norwegian colleagues measured the rate of change in score on the Mini-Mental State Examination in patients with Parkinson Disease and compared those changes to Mini-Mental State Examination changes of patients with Alzheimer disease and patients without dementia.

Patients with Parkinson disease and no cognitive impairment at onset of disease were enrolled; they participated in one or more assessments after their first visit including an examination at four years (visit two) and eight years (visit three). Motor, cognitive, and psychiatric symptoms were rated using standardized scales at visit one. Two population-based cohorts of patients with Alzheimer disease and patients without dementia were included for comparison.

A total of 129 Parkinson patients (57 percent women) were included. The average Mini-Mental State Examination score at visit one was 27.3. The average annual decline in score from visit 1 to visit 3 was 1.1 points (3.9 percent change). Patients with Parkinson disease and dementia (n=49) had an annual decline from visit one to visit two of 2.3 points (9.1 percent change), compared with 2.6 points (10.6 percent change) in patients with Alzheimer disease (n=34). The change in score for patients without dementia and Parkinson disease (n=80) was small and similar to that for control patients without dementia (n=1,621). Older age, hallucinations and more severe motor symptoms at the first visit were significantly associated with more rapid cognitive decline in patients with Parkinson disease.