Alzheimer's disease is the leading cause of dementia - a set of symptoms that includes: loss of memory, judgement, and reasoning; difficulty with day-to-day functions; changes in mood and behaviour.

To help you know what warning signs to look for, the Alzheimer Society has developed this checklist of common symptoms (some of them may apply to other forms of dementia).  Review the list - if you notice several symptoms, the person with the symptoms should see a doctor for a complete examination.

1. Memory loss that affects day-to-day function: It's normal to occasionally forget appointments, colleagues' names or a friend's phone number and remember them later.  A person with Alzheimer's disease may forget things more often and not remember them later, especially things that have happened more recently.
2. Difficulty performing familiar tasks: Busy people can be so distracted from time to time that they may leave the carrots on the stove and only remember to serve them at the end of a meal.  A person with Alzheimer's disease may be unable to prepare any part of a meal or forget they ate it.
3. Problems with language: Everyone has trouble finding the right word sometimes, but a person with Alzheimer's disease may forget simple words or substitute words, making his or her sentences difficult to understand.
4. Disorientation of time and place: It's normal to forget the day of the week or your destination - for a moment.  But a person with Alzheimer's disease can become lost on their own street, not knowing how they got there or how to get home.
5. Poor or decreased judgement: People may sometimes put off going to a doctor if they have an infection, but eventually seek medical attention.  A person with Alzheimer's disease may not recognize an infection as a problem or go to the doctor at all.  Or they may dress inappropriately, wearing heavy clothing on a hot day.
6. Problems with abstract thinking: From time to time, people may find balancing a cheque-book difficult.  Someone with Alzheimer's disease could forget completely what the numbers are and what needs to be dome with them.  Celebrating a birthday is something many people do, but a person with Alzheimer's disease may not understand what a birthday is.
7. Misplacing things: Anyone can temporarily misplace a wallet or keys.  A person with Alzheimer's disease may put things in inappropriate places: an iron in the freezer or a wristwatch in the sugar bowl.
8. Changes in mood and behaviour: Everyone becomes sad or moody from time to time.  Someone with Alzheimer's disease can exhibit varied mood swings - from calm to tears to anger - for no apparent reason.
9. Changes in personality: People's personalities can change somewhat with age. But a person with Alzheimer's disease can become confused, suspicious or withdrawn.  Changes may also include apathy, fearfulness or acting out of character.
10. Loss of initiative: It's normal to tire of housework, business activities or social obligations, but most people regain their initiative.  A person with Alzheimer's disease may become very passive, and require cues and prompting to become involved.