Alzheimer disease is a chronic, incurable brain disorder characterized by progressive loss of brain tissue and function. The early stages of Alzheimer disease primarily affect intellectual functions. Late-stage Alzheimer disease directly or indirectly affects other body systems. The condition is ultimately fatal.

According to 2105 data from the Centers for Disease Control and Prevention, Alzheimer disease (AD) is the sixth most common cause of death in the United States. AD describes a progressive degeneration of the gray matter of the brain, which controls thinking, memory, movement and sensation.