Simplify the following text for a Grade 5 native English-speaking person.
Original: Alzheimer 's disease ( AD ) , also called Alzheimer disease , senile dementia of the Alzheimer type , primary degenerative dementia of the Alzheimer 's type , or simply Alzheimer 's , is the most common form of dementia .
Simplified: Alzheimer 's Disease is not a normal part of aging .