Differences between Alzheimer’s and Parkinson’s

Do you know what the differences are between Alzheimer’s and Parkinson’s? First of all, say that these two diseases constitute two of the causes of dementia. Specifically, according to data from the WHO (World Health Organization), and In the case of Alzheimer’s, dementia from this disease represents 60-70% of all dementia cases.

However, these are two very different diseases; Furthermore, it should be clear that having either disease does not always lead to the development of dementia (although it is likely to do so). In this sense, we know that between 20-60% of people with Parkinson’s disease will develop dementia.

In a study by Buter et al. (2008), published in the magazine Neurologyin which 233 patients with Parkinson’s disease participated, it was observed how nearly 60% of them developed Parkinson’s dementia over a period of 12 years.

But what is dementia? With this concept we refer to the set of symptoms that arise as a consequence of neurological damage or disease. These symptoms imply the loss or weakening of mental faculties and mainly affect the cognitive area (memory loss, for example, or alterations in reasoning), the behavioral area (behavior alterations) and the personality area (changes in personality, irritability, emotional lability…).

Differences between Alzheimer’s and Parkinson’s

We are going to group the differences between Alzheimer’s and Parkinson’s into different blocks and explain what each of them consists of. All of them have been extracted from two reference psychopathology manuals: Belloch, Sandín and Ramos (2010) and the DSM-5 (APA, 2014).

The first block of differences between Alzheimer’s and Parkinson’s refers to their type of symptoms, which are the following:

Cognitive symptoms

The first difference between Alzheimer’s and Parkinson’s is found in their cognitive symptoms; In the case of Parkinson’s, memory failures appear in data retrieval, while in Alzheimer’s, failures occur in an earlier process in the memory process: data encoding. Besides, Memory and attention are more affected in Alzheimer’s than in Parkinson’s.

Motor symptoms

In the case of Parkinson’s, so-called parkinsonism appears., a clinical syndrome characterized by the following symptoms: rigidity, tremor, bradykinesia (slowing of movement), and postural instability. On the other hand, in Alzheimer’s it is very rare for parkinsonism to appear.

On the other hand, rigidity and bradykinesia appear very frequently in Parkinson’s, while in Alzheimer’s these symptoms appear only occasionally. Finally, tremor is a typical symptom in Parkinson’s but rare in Alzheimer’s.

Psychotic and other symptoms

In addition to the symptoms mentioned, others may appear in both Parkinson’s and Alzheimer’s; For example, in Alzheimer’s disease it appears delirium occasionally, while in Parkinson’s, it practically does not appear. Let us remember that the delirium It is a disorder of organic cause that mainly affects consciousness and attention.

As for psychotic symptoms, visual hallucinations can appear in both diseases (more or less in equal proportion). Delusions may also appear; in Alzheimer’s typically and in the case of Parkinson’s, occasionally.

Pathological symptoms

Another difference between Alzheimer’s and Parkinson’s has to do with the brain. (substances, neurotransmitters, atypical structures…). Thus, while senile plaques (extracellular deposits of molecules in the gray matter of the brain) typically appear in Alzheimer’s, these appear rarely in Parkinson’s.

The same thing happens with other structures, neurofibrillary tangles, which appear a lot in Alzheimer’s, but very rarely in Parkinson’s.

On the other hand, we find Lewy bodies more often in Parkinson’s than in Alzheimer’s. Regarding neurotransmitters, we know that many times a acetylcholine deficiency in the brain of people with Alzheimer’s, but this occurs only occasionally in people with Parkinson’s.

Finally, In Parkinson’s there is a dopamine deficiency, something that does not occur in Alzheimer’s.

Age of appearance

The age of onset is another of the differences between Alzheimer’s and Parkinson’s; in this sense, Parkinson’s usually appears before Alzheimer’s (that is, at 50-60 years old, compared to 65 or more with Alzheimer’s).

Prevalence

The prevalence of Alzheimer’s dementia is higher than that of Parkinson’s dementia.; According to the DSM-5 (2014), this is 5.5% in Spain and 6.4% in Europe.

Type of dementia

Finally, we know that In the case of Alzheimer’s, the dementia (not the disease) appears earlier than in the case of Parkinson’s.

Regarding the type of dementia, in Alzheimer’s it is cortical type (which implies involvement of the cerebral cortex), while Parkinson’s dementia is subcortical type (which implies involvement of the subcortical areas of the brain).

In this sense, we know that Cortical dementias generally involve cognitive symptoms, while subcortical dementias generally involve motor symptoms. (although both types of symptoms can be combined to a greater or lesser extent).

Let us remember here that cortical dementias include: Alzheimer’s, frontotemporal dementia, Creuzfeldt Jacob dementia and Lewy body dementia, while subcortical dementias include Parkinson’s, Huntington’s and HIV dementia, mainly.

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