Dementia and other cognitive problems for people with Parkinson’s vary widely and severity may fluctuate throughout the day.
Many people with Parkinson’s complain of changes in their thinking and mental abilities, but it should be stressed that comparatively few go on to develop dementia. However, it is thought that the majority of people with the disease experience some degree of cognitive impairment, albeit mild in many cases. One study found that after 10 years with Parkinson’s, 80% experienced cognitive difficulties1, whereas up to 30% developed dementia2.
Dementia appears to be more frequent in people with more pronounced bradykinesia (slow movement) and rigidity, and less frequent in those with more pronounced tremor.
Possible causes
Why dementia occurs in Parkinson's disease is not yet fully understood but the most likely causes are:
- advancing age - there is a much lower incidence of dementia in people under fifty. Usually a number of years pass from being diagnosed with Parkinson’s to the onset of dementia, maybe up to 15 years in some cases
- change in the structure and chemistry of the brain – it is believed that the process that causes dopamine cells in the substantia nigra part of the brain to prematurely die – known as neurodegeneration - is responsible for cognitive changes
- microscopic deposits, or Lewy bodies – these occur in nerve cells in the brain stem (see Different types of dementia).
Other possible reasons include:
- changes in the brain caused by Alzheimer’s (see Different types of dementia) or multiple small strokes
- sleep disturbance and fatigue – these factors can impact on concentration and memory
- psychological factors - mental deterioration, stress, depression and anxiety. (Be aware that depression can initially be wrongly diagnosed as dementia).
Often both biological and psychological factors are involved and if you experience any of the problems listed above it is important to consult your doctor. Treating such symptoms will not only increase your chances of alleviating your cognitive difficulties but will also enhance your quality of life.
