"Alzheimer's Disease" is the term used to describe a dementing disorder marked by certain brain changes, regardless of the age of the onset. Alzheimer's Disease is not a normal part of aging, and it is not something that inevitably happens in life. Rather, it is one of the dementing disorders, a group of brain diseases that lead to the loss of mental and physical functions. This disorder, whole cause unknown, affects a small, but significant percentage of older Americans. A very small minority of Alzheimer's patients are under 50 of age. However, most are over 65 years of age.