Differentiation of the dementias of Alzheimer's and Parkinson's disease with the dementia rating scale.

The Mattis Dementia Rating Scale (DRS) was used to distinguish between 50 dementia of the Alzheimer's type (DAT) and 50 Parkinson's disease (PD) subjects matched for age, education, and DRS total score. Despite a similar level of overall cognitive impairment, the DAT group earned significantly lower scores than did the PD group on the Memory subscale, while the PD group displayed lower scores than did the DAT subjects on the Construction subscale. Ajackknifed, stepwise, linear discriminant function using the five DRS subscales revealed that the Memory, Construction, and Initiation subtests significantly distinguished the groups. These results suggest qualitative differences in the dementias of DAT and PD patients and reveal that such differences can emerge on brief mental status examinations.