Alzheimer disease (AD) is an irreversible form of dementia characterized by memory loss, a progressive decline in intellectual ability, deteriorating language and speech skills, and personality and behavioral changes that eventually interfere with daily living. Currently, Alzheimer disease has been estimated to affect more than 5 million Americans.
Although some aspects of AD mimic changes found in the brain as we age, AD is not a normal part of the aging process. Due to the build-up of abnormal protein structures in the brain called senile plaques (SPs) and neurofibrillary tangles (NFTs), nerve cell injury and cellular death occur. The destruction of nerve cells also results in decreased levels of substances called neurotransmitters (the most important being acetylcholine) that help transmit brain signals. Over time, AD results in decreased interaction between different areas of the brain.