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What Is Alzheimer's Disease?

Know the signs, symptoms and stages of Alzheimer's

Adapted from NIH/National Institute on Aging | September 25, 2012
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All of us forget someone’s name or misplace things from time to time. This kind of forgetfulness is normal.

But forgetting how to get home, being confused in places a person knows well or asking questions over and over can be signs of a more serious problem. The person may have Alzheimer’s,  a disease of the brain that begins slowly and gets worse over time.

Alzheimer’s disease is an irreversible, progressive brain disease that slowly destroys memory and thinking skills and eventually the ability to carry out even the simplest tasks. In most people with Alzheimer’s, symptoms first appear after age 60. Alzheimer’s disease is the most common cause of dementia among older people. Dementia is the loss of cognitive functioning—thinking, remembering and reasoning—to such an extent that it interferes with a person’s daily life and activities. Estimates vary, but experts suggest that as many as 5.1 million Americans may have Alzheimer’s.

Who Discovered Alzheimer's? 

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, he examined 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.

Alzheimer's begins when tangles begin to develop deep in the brain, in an area called the entorhinal cortex, and plaques form in other areas.  As more and more plaques and tangles form in particular brain areas, healthy neurons begin to work less efficiently. They lose their ability to function and communicate with each other, and eventually they die.

This damaging process spreads to a nearby structure, called the hippocampus, which is essential in forming memories. As the death of neurons increases, affected brain regions begin to shrink. By the final stage of Alzheimer’s, damage is widespread and brain tissue has shrunk significantly.

Very Early Signs and Symptoms

Memory problems are one of the first signs 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 as those with Alzheimer’s. More people with MCI, compared with those without MCI, go on to develop Alzheimer’s.

Other changes may also signal the very early stages of Alzheimer’s disease. For example, brain imaging and biomarker studies of people with MCI and those with a family history of Alzheimer’s are beginning to detect early changes in the brain like those seen in Alzheimer’s. These findings will need to be confirmed by other studies but appear promising. Other recent research has found links between some movement difficulties and MCI. Researchers also have seen links between some problems with the sense of smell and cognitive problems. Such findings offer hope that some day we may have tools that could help detect Alzheimer’s early, track the course of the disease, and monitor response to treatments.

Mild Alzheimer’s Disease

As Alzheimer’s disease progresses, memory loss continues and changes in other cognitive abilities appear. Problems can include getting lost, trouble handling money and paying bills, repeating questions, taking longer to complete normal daily tasks, poor judgment, and small mood and personality changes. People often are diagnosed in this stage.

Moderate Alzheimer’s Disease

In this stage, damage occurs in areas of the brain that control language, reasoning, sensory processing, and conscious thought. Memory loss and confusion increase, and people begin to have problems recognizing family and friends. They may be unable to learn new things, carry out tasks that involve multiple steps (such as getting dressed), or cope with new situations. They may have hallucinations, delusions and paranoia, and they may behave impulsively.

Severe Alzheimer’s Disease

By the final stage, plaques and tangles have spread throughout the brain and brain tissue has shrunk significantly. People with severe Alzheimer’s cannot communicate and are completely dependent on others for their care. Near the end, the person may be in bed most or all of the time as the body shuts down.

More:
Alzheimer's: Causes and diagnosis
Common drugs for treating Alzheimer's
Genes offer clues to Alzheimer's disease

Part of a series on understanding and managing Alzheimer's Disease based on editorial content provided by the Alzheimer's Disease Education and Referral (ADEAR) Center and the National Institute on Aging's Age Page series.