OK, I am going to break your question down into two parts:
Currently the exact cause of Alzheimer’s disease is still not full known. What is known, however, is that the cause of the symptoms is build up by proteins in the brain. This build up results in the Plaques (the build up of the protein beta-amyloid that accumulate in the spaces between nerve cells) and Tangles (deposits of the protein tau that accumulate inside of nerve cells).
Here is a list of the top 10 symptoms of Alzheimer’s disease from ALZ.org. Also, if you notice any of them, please see a doctor.
Memory loss that disrupts daily life
Challenges in planning or solving problems
Difficulty completing familiar tasks at home, at work or at leisure
Confusion with time or place
Trouble understanding visual images and spatial relationships
New problems with words in speaking or writing
Misplacing things and losing the ability to retrace steps
Decreased or poor judgment
Withdrawal from work or social activities
Changes in mood and personality