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Alzheimer's Disease Fact Sheet

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Alzheimer’s disease is an irreversible, progressive brain disease that slowly destroys memory and thinking skills, and eventually even the ability to carry out the simplest tasks. In most people with Alzheimer’s, symptoms first appear after age 60. Estimates vary, but experts suggest that as many as 5.1 million Americansmay have Alzheimer’s disease.
Alzheimer’s disease is the most common cause of dementia among older people. Dementia is the loss of cognitive functioning—thinking, remembering, and reasoning—and behavioral abilities, to such an extent that it interferes with a person’s daily life and activities. Dementia ranges in severity from the mildest stage, when it is just beginning to affect a person’sfunctioning, to the most severe stage, when the person must depend completely on others for basic activities of daily living.
Alzheimer’s disease is named after Dr. Alois Alzheimer. In 1906, Dr. Alzheimer noticed changes in the brain tissue of a woman who had died of an unusual mental illness. Her symptoms included memory loss, language problems, and unpredictable behavior. After she died, heexamined her brain and found many abnormal clumps (now called amyloid plaques) and tangled bundles of fibers (now called neurofibrillary tangles). Plaques and tangles in the brain are two of the main features of Alzheimer’s disease. The third is the loss of connections between nerve cells (neurons) in the brain.  
Changes in the Brain in Alzheimer’s Disease
Although we still don’t know how theAlzheimer’s disease process begins, it seems likely that damage to the brain starts a decade or more before problems become evident. During the preclinical stage of Alzheimer’s disease, people are free of symptoms but toxic changes are taking place in the brain. Abnormal deposits of proteins form amyloid plaques and tau tangles throughout the brain, and once-healthy neurons begin to work less efficiently.Over time, neurons lose their ability to function and communicate with each other, and eventually they die.
Before long, the damage spreads to a nearby structure in the brain called the hippocampus, which is essential in forming memories. As more neurons die, affected brain regions begin to shrink. By the final stage of Alzheimer’s, damage is widespread, and brain tissue has shrunksignificantly.
Very Early Signs and Symptoms
Memory problems are typically one of the first warning signs of cognitive loss, possibly due to the development of Alzheimer’s disease. Some people with memory problems have a condition called amnestic mild cognitive impairment (MCI). People with this condition have more memory problems than normal for people their age, but their symptoms are not as severe asthose seen in people with Alzheimer’s disease. Other recent studies have found links between some movement difficulties and MCI. Researchers also have seen links between MCI and some problems with the sense of smell. The ability of people with MCI to perform normal daily activities is not significantly impaired. However, more older people with MCI, compared with those without MCI, go on to developAlzheimer’s.
A decline in other aspects of cognition, such as word-finding, vision/spatial issues, and impaired reasoning or judgment, may also signal the very early stages of Alzheimer’s disease. Scientists are looking to see whether brain imaging and biomarker studies, for example, of people with MCI and those with a family history of Alzheimer’s, can detect early changes in the brain like thoseseen in Alzheimer’s. Initial studies indicate that early detection using biomarkers and imaging may be possible, but findings will need to be confirmed by other studies before these techniques can be used to help with diagnosis in everyday medical practice.
These and other studies offer hope that someday we may have tools that could help detect Alzheimer’s early, track the course of the disease,...