Alzheimer’s disease, which affects more than 5 million Americans, is a brain disorder that over time destroys a person’s memory and ability to learn, reason, make judgments, communicate and perform daily activities. The disease usually begins after age 60, with the risk going up with age. It is estimated that about half of the population 85 and older has Alzheimer’s; therefore, it is not an inevitable part of aging. Rarer forms of the disease can occur earlier in life. The brains of people with Alzheimer’s are characterized by having clumps, called amyloid plaques, and tangled fibers, called neurofibrillary tangles, but what causes them remains an active area of research. Genetics and aspects of aging may play a role in creating the brain changes that most likely cause the disease symptoms. As Alzheimer’s progresses, individuals may experience changes in personality and behavior, including anxiety, suspiciousness, agitation, delusions and hallucinations. Disease course varies with each individual, but the average person lives 8 to 10 years after diagnosis. No cure currently exists for Alzheimer’s and drugs have variable effectiveness, but considerable research about the disease is leading to new approaches to drugs. Effective care and support has been shown to improve the quality of life for people with Alzheimer’s and their caregivers.