Annual decline in cognitive functioning is similar in patients with Parkinson disease and dementia and patients with Alzheimer disease

The average annual decline in cognitive functioning is similar in patients with Parkinson disease (PD) and dementia and patients with Alzheimer disease (AD), according to an article in the December issue of The Archives of Neurology, one of the JAMA/Archives journals.

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 PD, and the results vary considerably.

Dag Aarsland, M.D., Ph.D., of Rogaland Central Hospital, Hillevag, Norway, and colleagues measured the rate of change in score on the Mini-Mental State Examination (a test of cognitive functioning) in patients with PD and compared those changes to Mini-Mental State Examination changes of patients with AD and patients without dementia.

Patients with PD were selected from a community-based cohort in Rogaland County, Norway. Patients with no cognitive impairment at the onset of their disease and who participated in one or more assessments after their first visit were included and examined again after 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.

One hundred twenty-nine PD patients (57 percent women) were included in the study. 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 PD 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 AD (n=34). The change in score for patients without dementia and PD (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 PD.