Alzheimer's, is a very scary disease. When you are young you don't really think about growing old and losing most of your memory, until a loved one is diagnosed with a very confusing disease.
My grandmother was diagnosed with Alzheimer's Disease a year or so back. All I thought was she was forgetful, I didn't realize she wouldn't know who I was or that her whole personality would change. She doesn't know where she is half the time and the other half she doesn't understand whats going on. She will get up at random times and insist we are going places, or when we have to go places she insists that we have to stay.
The issue with the disease is there is no normal, with one person they may just forget who you are and with others they may think you are the enemy and you want to hurt them. They may think people you don't know are related to you and they may think that there son or daughter is there spouse.
It gets very frustrating at times, but you have to understand that they are just as confused as you are. I may only be 19 but I still do my best to be there for her, it is stressful, but she needs me even if she doesn't always know who I am.