Sometimes dementia symptoms can be caused by conditions that may be treatable, such as depression, thyroid disease, infections or drug interactions. If the symptoms are not treatable and progress over time, they may be due to damage to the nerve cells in the brain.

Alzheimer's disease, the most common form of dementia, accounts for 64 per cent of all dementias in Canada. The features of Alzheimer's disease include a gradual onset and continuing decline of memory, as well as changes in judgment or reasoning, and the inability to perform familiar tasks.

Sometimes a person may have symptoms such as sudden onset of memory loss, early behaviour changes, or difficulties with speech and movement. These symptoms may suggest a dementia other than Alzheimer's disease.

A person should seek a thorough medical assessment if any of the above symptoms are present.