What is Dementia?

Dementia is an umbrella term describing a set of symptoms that impair brain function to the point where a person has problems with day-to-day activities.

Some common types of dementia are:

In some cases, people may experience more than one type of dementia. Mixed dementia is a term used when there are multiple causes that are contributing to someone’s thinking and memory problems. For example, if vascular dementia co-occurs with Alzheimer’s disease, a person would have mixed dementia and may experience signs and symptoms from both conditions.

Signs and Symptoms of Dementia

Signs and symptoms of dementia can vary depending on the type of dementia. Some common signs and symptoms can include:

Memory loss

For example, trouble remembering appointments or learning new information

Difficulty finding words

For example, 'tip-of-the-tongue' phenomenon when looking for words

Trouble with orientation & getting around

For example, getting lost in familiar surroundings

Difficulty planning or problem solving

For example, difficulty planning what to wear or cooking from a recipe

Difficulty with coordinating complex motor tasks

For example, trouble building a shelf using instructions, increased risk of falls

In addition to changes in thinking and memory, dementia can also cause changes to someone’s mood and personality. Some of these changes can include:

  • Depression (e.g., long periods of low mood and sadness that affect daily functioning)
  • Agitation (e.g., becoming excitable or restless)
  • Lack of interest in activities (known as 'apathy')
  • Delusions (e.g., believing someone is after you, or that you are invincible)
  • Hallucinations (e.g., hearing voices or seeing something that is not there)
  • Trouble sleeping
  • Inappropriate behavior (e.g., inappropriate sexual behaviours)
  • Personality changes (e.g., someone who is typically calm becoming quick to anger and aggressive)

What Causes Dementia?

Dementia is caused by physical changes to the brain, and should not be confused with healthy aging or temporary conditions that can affect thinking and memory (e.g., delirium following surgery or prolonged illness).

Humans have around 100 billion brain cells, which are called neurons. Neurons talk to each other and form the connections needed for our thinking and memory. Dementia causes damage to these neurons, which can interfere with their ability to communicate with each other. The cause of the damage depends on the type of dementia.


Most types of dementia cannot be diagnosed with just one test. However, a combination of thinking and memory tests, brain imaging (usually an MRI brain scan), physical exams, laboratory testing, and an understanding of the person’s medical history and symptoms can help doctors make a diagnosis. It is also very helpful for someone who knows the patient well to provide information about their thinking and behaviour on a daily basis.

Usually, a doctor can accurately make a diagnosis of dementia, but it is harder to identify which type of dementia a patient may have. An appointment with a more specialized doctor such as a neurologist, geriatrician, psychiatrist, or movement disorder specialist may be needed to get a specific diagnosis.


There is currently no cure to stop or slow down the disease progression of dementia. There are medications approved for use in Canada that can temporarily improve some of the symptoms. Please speak with your doctor about your treatment options.

In order to find a cure and new treatments for dementia, more research is needed. Volunteers are invaluable to research. Find out more about research and how you can participate

Learn More about the Common Types of Dementia

Alzheimer's Disease 

Alzheimer’s disease is the most common cause of dementia, making up about 60-80% of dementia cases.

Some signs of Alzheimer’s disease include:

  • Slowed thinking
  • Poor memory (e.g., forgetting to take medication, forgetting appointments)
  • Difficulty planning or solving problems
  • Confusion about date and location
  • Language difficulties (e.g., word finding difficulties, repetitive, trouble naming a familiar object)
  • Changes in mood and emotions

As a person ages, there can be a slight decline in memory and thinking abilities. However, Alzheimer’s disease is not part of healthy aging.

Alzheimer’s disease is caused by the build-up of two proteins in the brain called 'plaques' and 'tangles'. Plaques are formed when a protein outside of a brain cell called beta-amyloid clumps together. Tangles are formed when a protein inside of a brain cell called tau twists together. The formation of these plaques and tangles interferes with the ability of brain cells to communicate with one another, and as a result, causes them to die over time.

Alzheimer’s disease and the build-up of these proteins usually begins in the part of the brain that is responsible for memory, known as the hippocampus, and then spreads to other parts of the brain. This is why problems with memory are the first signs of Alzheimer’s disease, although other symptoms can develop over time. 

Participate in Alzheimer's disease research

Vascular Cognitive Impairment/Vascular Dementia

Vascular dementia is the second most common cause of dementia, making up around 20% of dementia cases. Vascular dementia is caused by damage to blood vessels in the brain, which can happen after a stroke. When this damage occurs, brain cells are not able to receive all of their nutrients and oxygen to function properly.

The symptoms of vascular dementia can vary depending on where the damage occurred, and how severe it is. If the symptoms are milder (e.g., confusion, trouble with concentration, slowed thinking), then a diagnosis of vascular cognitive impairment is given. If the symptoms are severe enough to interfere with day-to-day functioning (e.g., trouble with processing information, reasoning, or finding your way around), then a diagnosis of vascular dementia is given.

Participate in vascular cognitive impairment/vascular dementia research. 

Parkinson’s Disease Dementia/Lewy Body Dementia

Lewy body dementia (LBD) and Parkinson’s disease dementia (PDD) are types of dementia that are caused by proteins in the brain called 'alpha synuclein', which clump together to form Lewy bodies. LBD is the third most common cause of dementia, accounting for about 5-10% of cases.

As LBD and PDD share very similar features and have the same cause, many experts consider them the same disease but with different signs and symptoms. If motor symptoms appear first, such as tremors, shuffled walking or rigid muscles, then a diagnosis of PDD is given. If dementia symptoms occur before the motor symptoms, then a diagnosis of LBD is given. 

Some signs and symptoms of LBD and PDD include:

  • Problems with thinking and reasoning
  • Difficulty with movements (e.g., rigid muscles, shuffling walk, trouble initiating movements)
  • Fluctuation in alertness and thinking, which can vary day to day or from morning to evening
  • Delusions
  • Hallucinations (e.g., hearing voices or seeing things that are not there)
  • Sleep disturbances
  • Nervous system changes (e.g., a sudden drop in blood pressure when standing up, incontinence)

Participate in LBD/PDD research

Frontotemporal Dementia

Frontotemporal dementia (FTD) is caused by damage to the frontal and temporal lobes of the brain, impairing the functions of those areas.

There are three subtypes of frontotemporal dementia: 

1. Behavioural variant frontotemporal dementia (bvFTD)

The bvFTD type, the most common type of FTD, involves changes in personality, behaviour, and judgement. For example, a person living with bvFTD can lose social etiquettes and act inappropriately in public (e.g., temper tantrums, touching strangers, public urination). A person’s memory may remain intact, at least in the early stages of the disease.

2. Primary progressive aphasia (PPA)

In the PPA type, language abilities such as speaking, writing, and understanding language are affected. PPA can be subcategorized into:

  • Semantic type: A person can lose their ability to use and understand language
  • Progressive nonfluent aphasia/agrammatic type: A person has trouble producing speech

3. Movement Disorders

This type of frontotemporal dementia involves problems with movement. Behavioural and language problems may or may not be present as well.

There are 3 disorders that are part of this subtype of frontotemporal dementia:

  • Corticobasal syndrome (CBS): A person can experience increased difficulty with coordination, movement, speech, and thinking
  • Progressive supranuclear palsy (PSP): A person can experience vision difficulties and loss of balance while walking
  • Amyotrophic lateral sclerosis (ALS), aka Lou Gehrig’s disease: A person experiences loss of control of the muscles that control movement, speech, eating, and breathing

The cause(s) of frontotemporal dementia are not well known. However, researchers have found some genes linked to frontotemporal dementia that account for one third of all cases.

Participate in FTD research 

Related Conditions

Mild Cognitive Impairment

A person living with mild cognitive impairment (MCI) may experience some thinking, memory, and language difficulties. The changes are more severe than that of healthy aging, and may be noticed first by family and friends. However, these changes are not severe enough to interfere with day-to-day functioning.

While having MCI can increase one’s risk of developing Alzheimer’s disease or another form of dementia, not everyone living with MCI will develop dementia. Some people living with MCI remain stable for many years.

MCI is classified based on which thinking skills are affected:

Amnestic MCI: Primarily affects memory. A person can begin to forget information that they would have previously easily recalled (e.g., appointments, conversations, recent events).

Nonamnestic MCI: Affects thinking skills other than memory, including decision-making, judgement of the time or sequence of steps to complete a task, and visual perception.

Participate in MCI research