Although we still don’t know what starts the Alzheimer’s disease process, we do know that damage to the brain begins as many as 10 to 20 years before any problems are evident. 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. Then, 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 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.
Alzheimer's disease develops slowly and causes changes in the brain long before there are obvious changes in a person's memory, thinking, use of words or behavior. Stages and changes the person will go through are outlined below.