What is Alzheimer's Disease?
Alzheimer's disease is a progressive disease. (It gets worse with age) Alzheimer's is NOT a normal way for aging to happen.
dementia and memory loss
Most cases dealing with APP, PSEN1, or PSEN2. Also it follows a dominant pattern. Other cases?
It is uncertain how... thought to be linked to APOE e4 allele... getting one copy increases risk, getting to copies increases chances further. Though this allele increases your chances of developing Alzheimer's, not everyone with Alzheimer's has even one of these alleles. It just increases chances.