What is mixed dementia?
Because different types of dementia can have different causes, it's possible for a person to have more than one type of dementia. When this happens, that person has mixed dementia.
A person living with mixed dementia will show symptoms of at least two different types of dementia. Usually, mixed dementia consists of the two most common types: Alzheimer’s disease and vascular dementia.
For example, a person with mixed dementia may show symptoms of both Alzheimer's and vascular dementia. Because many symptoms overlap between different types of dementia, it can be hard to figure out if someone has mixed dementia.
However, it's important that we are aware whether someone has mixed dementia, because the combination of two or more dementias will likely have a greater impact on their brain than experiencing one disease alone. This can affect how a person progresses through the stages of dementia.
How many people have mixed dementia?
Researchers don’t know exactly how many people currently diagnosed with a specific type of dementia actually have mixed dementia. However, autopsy studies indicate that mixed dementia may be much more common than previously realized.
Why do we perform autopsy studies? Autopsy studies play a key role in shedding light on mixed dementia because scientists can't yet measure most dementia-related brain changes in living individuals.
Some experts recommend suspecting mixed dementia whenever a person has both evidence of cardiovascular disease and dementia symptoms that get worse slowly over time. Evidence like this may indicate the presence of both Alzheimer's disease and vascular dementia.
How can mixed dementia be treated?
Like any other dementia, the best way to treat the effects of mixed dementia is to follow a brain-healthy lifestyle. This also holds true for reducing the risk of mixed dementia.
Depending on the symptoms experienced, someone living with mixed dementia may find relief with medications approved to treat Alzheimer's disease as well as certain alternative treatments. Before starting any treatment, however, the Alzheimer Society strongly recommends checking with a doctor or a qualified healthcare provider first.
More useful links and resources
Mixed dementia.Alzheimer's Association. This U.S.-focused webpage covers symptoms, diagnosis, risk factors and treatment for mixed dementia.
Overview
While the terms "Alzheimer's disease" and "dementia" are often used interchangeably, it's important to know the difference between the two.
- Dementia is not one specific disease. Rather, it's an umbrella term for a set of symptoms caused by physical disorders affecting the brain.
- Alzheimer's disease is the most common cause for dementia, accounting for 60-80% of all diagnoses.
Overall, know that Alzheimer's disease is a specific disease, while dementia is a general term for a group of similar diseases, of which Alzheimer's is one.
In other words, every case of Alzheimer's disease is an example of dementia, but not every type of dementia is Alzheimer's.
Symptoms
The symptoms of dementia include:
- Memory loss, both short-term and long-term,
- Difficulties with thinking, problem-solving or language that are severe enough to reduce a person's ability to perform everyday activities, and
- Changes in mood or behaviour.
The symptoms for Alzheimer's disease mostly overlap with other types of dementia, but there can be some differences.
For example:
Other dementias can focus more on certain symptoms, and less on others. In the case of frontotemporal dementia, changes in personality are more apparent in the early stage, while memory decline often doesn't arise until the later stage.
Affected areas of the brain
The differences in symptoms can be explained by the area of the brain each type of dementia affects.
For example:
While Alzheimer's disease generally affects most of the brain, frontotemporal dementia primarily affects the frontal and temporal lobes of the brain – the areas generally associated with personality and behaviour.
This explains why changes in personality are usually more obvious in the early stage of frontotemporal dementia than in the early stage of Alzheimer's.
Risk factors
Risk factors between different types of dementia also overlap, but there are some types that are more determined by a certain risk factor than others.
For example:
Stroke is now understood to be a common cause of vascular dementia. When a stroke occurs and the brain’s blood supply is blocked or damaged, brain cells are deprived of oxygen and die, leading to dementia. Because of that, having a stroke increases the risk of getting vascular dementia.
Genetics are a pronounced risk factor for Creutzfeldt-Jakob disease, one of the rarest types of dementia. If a parent has a mutation in their human prion protein gene, the chances that they will pass down Creutzfeldt-Jakob disease is 50% for each child.