Alzheimer Disease

Other changes occur in the brain of a patient with the disease. For example, there is a loss of nerve cells in the brain, especially in the area of the brain associated with memory. In addition, there is a loss of the chemical neurotransmitter called acetylcholine. This chemical aids in the transmission of signals from one nerve to another in the brain. The loss of acetylcholine means that brain signals are not transmitted through the brain as well as in people who do not have Alzheimer disease.

Alzheimer disease is a progressive disorder. The formation of the amyloid plaques, loss of nerve cells, and loss of acetylcholine occurs over time. Thus, the deterioration in brain function occurs gradually in an Alzheimer's patient. The disease is also associated more with older people (i.e., 60 and older) than with younger people. Only about three percent of people ages 65 to 74 have the disease, whereas nearly half of all those 85 and older may have the disease.

The reasons for the formation of amyloid plaques and neurofibrillary tangles are not clear.