Dementia Defined

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Padmaja Genesh from the Alzheimer Society of Calgary explains the most common types of dementia.


Alzheimer’s disease

Alzheimer’s disease is the most common type of dementia, affecting more than 564,000 people across Canada.

“What happens in Alzheimer’s disease is that some change is happening in the brain that is causing the nerve cells to die and causing different parts of the brain to shrink,” Genesh says.

It is characterized by memory loss that is severe enough to impact a person’s daily life, as well as changes in a person’s problem-solving abilities, confusion and difficulty completing familiar, routine tasks.

Vascular dementia

“A person gets vascular dementia when the blood flow to a particular part of the brain is compromised or blocked,” Genesh says.

This, she explains, can either be the result of a single stroke that has affected a large part of the brain, or it can follow a series of mini-strokes affecting smaller areas of the brain.

As a result, cognitive abilities such as speech, sight or memory may be altered, depending on the area of the brain that is affected.

Lewy body dementia

Dementia with Lewy bodies

Difficulty in thinking and reasoning, and changes in alertness that varies from day to day or at different times of the day, are some of the main hallmarks of dementia with Lewy bodies. This type of dementia is caused by abnormal protein deposits in different parts of the brain, which were first identified by Dr. Frederich Lewy and were called Lewy bodies.

“One [of the main symptoms of this form of dementia] is fluctuating cognition,” Ganesh says. “Sometimes the person is performing very well, and remaining very alert, but at other times they may function very poorly and be very confused.”

Another symptom of dementia with Lewy bodies is visual hallucinations — in other words, seeing things that are not there. And a third symptom is when an individual displays the characteristics of Parkinson’s disease, which can include slow, sluggish movements or difficulty walking.

Parkinson’s disease dementia

“Both Parkinson’s disease dementia and dementia with Lewy bodies are different forms of Lewy body dementia,” explains Genesh.

While dementia with Lewy bodies and Parkinson’s disease dementia are quite similar, the main differentiating factor is when cognitive decline takes place in the individual.

In cases of dementia with Lewy bodies, cognitive challenges happen in conjunction with, or even before, the movement challenges of Parkinson’s disease arise. In Parkinson’s disease dementia, a person already living with Parkinson’s develops symptoms of dementia
a year or more after their diagnosis.

Genesh says that those living with Parkinson’s disease for more than a decade are more susceptible to developing symptoms of dementia. Parkinson’s disease dementia can be characterized by memory problems, reduced attention span, and encountering problems with decision-making and with finishing tasks.

Frontotemporal dementia

This form of dementia most commonly affects people between the ages of 40 and 70 and is caused by protein tangles, which cause cells to die in the frontal and temporal lobes of the brain.

Symptoms resulting from damage to the frontal lobes include changes in personality (such as a very friendly person becoming unfriendly), a lack of initiative or difficulty with decision-making, Genesh explains.

“The frontal lobe is the executive centre, so decision-making comes from there,” she says. “When that part of the brain is not working, there is a loss of inhibitions, which leads to inappropriate behaviour. So the person might say inappropriate things or do inappropriate things.”

Damage to the temporal lobes affects memory and language, including challenges with language fluency or a loss of vocabulary.

Young onset dementia

Approximately five to eight per cent of all dementia cases in Canada happen in people who are younger than 65 years of age. This type of dementia is referred to as young onset dementia. It is estimated by the Alzheimer Society of Canada that around 16,000 Canadians currently live with young onset dementia.

Genesh explains that there are a variety of causes for young onset dementia, including the inherited form of Alzheimer’s disease, frontotemporal lobe dementia, stroke, or damage due to alcohol or a traumatic brain injury. More than 50 per cent of those with Down syndrome, which is also known as trisomy 21, may also develop Alzheimer-type dementias if they live to the age of 60 or over.  [ ]

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MIXED DEMENTIA When two or more forms of dementia are present at the same time, this is referred to as mixed dementia. Although the most common combination is vascular dementia and Alzheimer’s disease, this term refers to any combination of dementia types. “It’s possible for someone to have Lewy body dementia and vascular dementia,” says Genesh. “Or, a person could have Alzheimer’s disease and Lewy body dementia — different combinations can be there.”