Differences Between Alzheimer’s And Parkinson’s

Do you know the differences between Alzheimer’s and Parkinson’s? These diseases are among the most common causes of dementia. Learn more about them on this post.

First, we must say that both of these diseases are two of the causes of dementia. However, it is important to keep in mind that these are two very different diseases. In addition, it should be made clear that having any of these conditions does not always lead to the development of dementia (although this occurs in most cases). 

In this sense, we know that  between 20 to 60% of people with Parkinson’s disease end up developing dementia.

In a study by Buter et al. (2008), published in the journal  Neurology, in which 233 patients with Parkinson’s disease participated, it was observed that about 60% of them developed Parkinson’s dementia over a 12-year period.

But what is dementia? This concept refers to the set of symptoms that arise as a result of neurological damage or disease. These symptoms involve the loss or weakening of the mental faculties and mainly affect three different areas: the cognitive area (loss of memory or changes in reasoning), the behavioral area (changes in behavior) and the personality area (changes in personality, irritability, emotional lability, among other things).

“There is nothing that is a clearer sign of dementia than doing something repeatedly and hoping that the results will be different.”
-Albert Einstein-

Differences between Alzheimer’s and Parkinson’s

We will group the differences between both diseases in different blocks and explain what each one consists of. All of them were extracted from two reference manuals in psychopathology.

The first block of differences between Alzheimer’s and Parkinson’s refers to their types of symptoms, which are as follows:

Cognitive symptoms

One of the main differences between these two diseases is related to the way they affect the cognitive area. In the case of Parkinson’s, there are failures in data recovery (memory), while in Alzheimer’s, failures occur previously in the memory process (data coding). In addition, the  memory and attention are most affected in Alzheimer’s than in Parkinson’s.

Motor symptoms

In the case of Parkinson’s, there is the so-called parkinsonism, a clinical syndrome characterized by the following symptoms: stiffness, tremor, bradykinesia (slow movement) and postural instability. In contrast, in Alzheimer’s, parkinsonism is very rare.

On the other hand, stiffness and bradykinesia appear very often 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 we have already mentioned, other symptoms can appear in both diseases. For example,  in Alzheimer’s disease, delirium appears occasionally, while in Parkinson’s disease it practically does not. It is important to remember that delirium is an organic disorder that mainly affects awareness and attention.

In relation to psychotic symptoms, visual hallucinations may appear in both diseases, more or less in the same proportion. There may also be delusions, being frequent in Alzheimer’s and occasional in Parkinson’s.

Pathological symptoms

Another difference between both diseases is related to the brain (substances, neurotransmitters and atypical structures). For example, while senile plaques typically appear in Alzheimer’s (extracellular deposits of molecules in the brain’s gray matter), in Parkinson’s they rarely appear.

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

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On the other hand, Lewy’s bodies appear more often in Parkinson’s than in Alzheimer’s. When it comes to neurotransmitters, we know that the  acetylcholine deficiency often occurs in the brains of people with Alzheimer’s, but only occasionally in people with Parkinson’s.

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

Age of onset

The age of onset is also different. The Parkinson’s usually appears between 50 and 60 years, appearing before Alzheimer’s, which usually appear from the age of 65.


The prevalence of Alzheimer’s dementia is higher than that of Parkinson’s dementia . According to DSM-5 (2014), it is 6.4% in Europe.

Parkinson in old people - differences between Alzheimer's and Parkinson's

Type of dementia

As for the type of dementia , in Alzheimer’s it is cortical (it involves the involvement of the cerebral cortex), while in Parkinson’s it is subcortical (it involves the subcortical areas of the brain).

In this sense, it is noteworthy that cortical dementias usually carry cognitive symptoms, while subcortical dementias carry motor symptoms. However, both types of symptoms can be combined to a greater or lesser extent.

It is worth remembering that cortical dementias include Alzheimer’s, frontotemporal dementia, Creuzfeldt-Jacob dementia and Lewy body dementia, while subcortical dementias include Parkinson’s, Huntington’s disease  and HIV dementia, mainly.


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