What is Alzheimer's disease?

Alzheimer's disease is a chronic neurodegenerative disease that destroys brain cells, causing thinking ability and memory to decline over time. Alzheimer's disease is not a normal part of aging, and is irreversible.

Senior woman smiling

Here are some important facts about Alzheimer's disease, the most common form of dementia.

We've only recently identified Alzheimer's as a serious and prevalent disease

Alzheimer's disease has been with us throughout human history. However, our understanding of it has been relatively recent:

  • In the last 100 years: Alzheimer's disease has been formally identified and named.
  • In the last 50 years: We've made serious advances to recognize the impact of Alzheimer's disease, and commit to finding treatments and a cure.
  • In the last 20 years: We've taken more steps to fight the stigma against the disease and support the voices of people living with Alzheimer's and their caregivers.

Plenty of progress has been made, and we still have ways to go.

Read more about the history behind Alzheimer's disease.

Alzheimer's disease is the most common type of dementia

Alzheimer's disease is the most common type of dementia, accounting for 60 to 80% of all cases of dementia.

However, it's not accurate to say that if a person has dementia, then they have Alzheimer's disease – or that all dementias are a type of Alzheimer's.

Know the difference between Alzheimer's disease and dementia.

Alzheimer's disease changes the brain

Alzheimer’s disease is a fatal disease that eventually affects all aspects of a person’s life – how they think, feel and act.

Each person is affected differently. While it's difficult to predict symptoms, the order in which they will appear or the speed of their progression, there are some warning signs you can look out for.

Learn more about how Alzheimer's disease changes the brain.

Alzheimer's disease is progressive

Alzheimer's disease is usually described in terms of stages, indicating the severity of the symptoms.

  • Early stage: Symptoms are mild. A person at this stage is fully aware of their condition and only needs minimal assistance, if requested.
  • Middle stage: Symptoms start becoming more noticeable. More assistance will be needed to help the person living with Alzheimer's disease accomplish daily tasks.
  • Late stage: Once the person reaches this stage, they will eventually be unable to communicate verbally or look after themselves. Quality of care is important to ensure that the person has quality of life.
  • End of life: Cognitive decline has progressed to the point where the person needs 24-hour care. The focus shifts to palliative care and comfort to ensure quality of death.

The earlier on in the disease that a person gets diagnosed, the higher the chances are for a better quality of life.

Learn more about the different stages of Alzheimer's disease.

In most cases, having family with Alzheimer's doesn't mean you will also get it

Most cases of Alzheimer’s disease are sporadic, meaning it has no specific family link.

Only rare instances of Alzheimer’s disease are inherited or familial, accounting for less than five percent of all cases. There is genetic testing available for families that have a history of this form of Alzheimer's disease.

Learn more about the genetics behind Alzheimer's disease.

You can reduce your risk of Alzheimer's disease

Reducing your risk by making brain-healthy lifestyle choices won't guarantee you won't get Alzheimer's, but it's still the most effective method of prevention.

Other alleged methods have not held up to scientific study, and more research needs to be done to conclusively show their effects.

Learn more about the risk factors for dementia.

The symptoms of Alzheimer's disease can be treated, but not cured...yet

There are several medications that can help with symptoms such as memory decline, changes in language, thinking abilities and motor skills.

Although there is still no cure for Alzheimer's disease, those who respond to these treatments can experience improvements in their quality of life for several years.

Researchers continue to search for more effective treatments for Alzheimer's disease, as well as as a cure. Thanks to their efforts, our understanding of Alzheimer's disease and other dementias become clearer with each day.

Learn more about the medications available to treat Alzheimer's disease.

You can still live well with Alzheimer's

If you've been recently diagnosed, first know that there are resources and help available to support you and your family.

While every journey is unique, and it will be difficult, know that there are people who live well with Alzheimer's disease and other dementias.

Research shows that there are many things that can help you live well with Alzheimer’s disease. Making healthy lifestyle choices may improve your quality of life and make it easier to manage the changes that the disease brings.

By getting the support you need as quickly as possible, you can maintain a high quality of life while living with Alzheimer's disease for as long as possible.

Find out what steps to take after diagnosis.

More useful links, downloads and resources


What is Alzheimer's disease? | (Print-friendly version) Alzheimer Society of Canada. This print-friendly, downloadable PDF brochure gives an overview of what Alzheimer's disease is, including what we know so far from research, its effects and risk factors.

This webpage was last updated on April 16, 2024. If you have comments, questions or suggestions about this page, please email publications@alzheimer.ca.