The most common cognitive disorder, particularly among the elderly, is Alzheimer’s disease (AD), accounting for approximately two thirds of all dementia. There is some overlap of symptoms and biological changes in both Parkinson’s and Alzheimer’s and they can co-exist, although this is uncommon. Most people with Parkinson’s who develop dementia do so as a result of Parkinson’s rather than cognitive difficulties. Memory loss in Parkinson’s is generally thought to be less severe than in Alzheimer’s and more subtle in nature, although this of course varies from person-to-person.
There are two types of pathological change found in people with Parkinson’s and dementia:
- Lewy Bodies, or protein deposits, in the nerve cells
- Alzheimer-type changes, such as ‘plaques' and 'tangles' which develop in the structure of the brain and lead to the death of brain cells.
In about 25% of dementia cases for people with Parkinson’s, there are only Lewy bodies occupying the brain and brainstem1. In the remaining 75%, Lewy bodies are seen in the brain stem together with Alzheimer’s-type changes in the brain, similar to Dementia with Lewy Bodies.
