People with Parkinson’s disease who develop dementia have a decline in mental abilities similar to the rate seen in people with Alzheimer’s disease - despite the fact that Parkinson’s and Alzheimer’s are quite different disease - a Scandinavian study indicates

Knowing the rate of mental decline in dementia related to Parkinson’s disease allows patients and caregivers to prepare for future needs, Dr. Dag Aarsland and colleagues note in their report, published in the Archives of Neurology.

Aarsland, at the University of Bergen in Norway, and his team followed 129 patients with Parkinson’s disease who underwent testing of their mental performance at the start of the study and again after 4 years and after 8 years.

None of the participants had dementia at the first visit, but 49 had developed the condition by the second visit.

The researchers compared these findings with those documented among 34 people with Alzheimer’s disease and 1621 normal “control” subjects without dementia who were tested initially and again 5 years later.

Average scores on a standard mental performance test among those diagnosed with Parkinson’s dementia were 25.4 at the first evaluation, 16.2 at the second visit and 7.2 at the third, corresponding to an average annual decline ranging of 2.3 to 2.4.

The Alzheimer’s disease patients exhibited an annual decline of 2.8, similar to the Parkinson’s disease patients with dementia.

In contrast, 36 patients with Parkinson’s disease completed the 8-year follow-up without developing dementia, and these subjects exhibited declines that were similar to the normal control subjects.

SOURCE: Archives of Neurology, December 2004.