Alzheimer’s disease is a brain disorder named for German physician Alois Alzheimer, who first described it in 1906. Scientists have learned a great deal about Alzheimer’s disease in the century since Dr. Alzheimer first drew attention to it. Today we know that Alzheimer’s:
- Is a common and serious brain disease. More than 5 million Americans now have Alzheimer’s. Although symptoms can vary widely, the first problem many people notice is forgetfulness severe enough to affect their work, lifelong hobbies or social life.
- Gets worse over time. As the disease progresses, other symptoms include confusion, trouble with organizing and expressing thoughts, misplacing things, getting lost in familiar places, and changes in personality and behavior. For more information, see Warning Signs or Stages of Alzheimer’s Disease.
- Is the most common form of dementia, a general term for the loss of memory and other intellectual abilities serious enough to interfere with daily life. Vascular dementia, another common type, is caused by reduced blood flow to parts of the brain. In mixed dementia, Alzheimer’s and vascular dementia occur together. For more information about other causes of dementia, please see Related Diseases.
- Has no current cure, But treatments for symptoms, combined with the right services and support, can make life better for the millions of Americans living with Alzheimer’s. We’ve learned most of what we know about Alzheimer’s in the last 15 years. There is an accelerating worldwide effort under way to find better ways to treat the disease, delay its onset, or prevent it from developing. Learn more about recent progress in Alzheimer science and research funded by the Alzheimer’s Association in the Research section.
Alzheimer's and the brain
Just like the rest of our bodies, our brains change as we age. Most of us notice some slowed thinking and occasional problems remembering certain things. However, serious memory loss, confusion and other major changes in the way our minds work are not a normal part of aging. They may be a sign that brain cells are failing.
The brain has 100 billion nerve cells (neurons). Each nerve cell communicates with many others to form networks.
Nerve cell networks have special jobs. Some are involved in thinking, learning and remembering. Others help us see, hear and smell. Still others tell our muscles when to move.
To do their work, brain cells operate like tiny factories. They take in supplies, generate energy, construct equipment and get rid of waste. Cells also process and store information. Keeping everything running requires coordination as well as large amounts of fuel and oxygen.
In Alzheimer’s disease, parts of the cell’s factory stop running well. Scientists are not sure exactly where the trouble starts. But just like a real factory, backups and breakdowns in one system cause problems in other areas. As damage spreads, cells lose their ability to do their jobs well. Eventually, they die.
History
At a scientific meeting in November 1906, German physician Alois Alzheimer presented the case of “Frau Auguste D.,” a 51-year-old woman brought to see him in 1901 by her family. Auguste had developed problems with memory, unfounded suspicions that her husband was unfaithful, and difficulty speaking and understanding what was said to her. Her symptoms rapidly grew worse, and within a few years she was bedridden. She died in Spring 1906, of overwhelming infections from bedsores and pneumonia.
Dr. Alzheimer had never before seen anyone like Auguste D., and he gained the family’s permission to perform an autopsy. In Auguste’s brain, he saw dramatic shrinkage, especially of the cortex, the outer layer involved in memory, thinking, judgment and speech. Under the microscope, he also saw widespread fatty deposits in small blood vessels, dead and dying brain cells, and abnormal deposits in and around cells.
The condition entered the medical literature in 1907, when Alzheimer published his observations about Auguste D. In 1910, Emil Kraepelin, a psychiatrist noted for his work in naming and classifying brain disorders, proposed that the disease be named after Alzheimer.
Cause:
While scientists know Alzheimer’s disease involves progressive brain cell failure, they have not yet identified any single reason why cells fail. However, they have identified certain risk factors that increase the likelihood of developing Alzheimer’s.
Risk factors:
Age
The greatest known risk factor for Alzheimer’s is increasing age. Most individuals with the disease are 65 or older. The likelihood of developing Alzheimer’s doubles about every five years after age 65. After age 85, the risk reaches nearly 50 percent.
Family history
Another risk factor is family history. Research has shown that those who have a parent, brother or sister, or child with Alzheimer’s are more likely to develop Alzheimer’s. The risk increases if more than one family member has the illness. When diseases tend to run in families, either heredity (genetics) or environmental factors or both may play a role.
Genetics (heredity)
Scientists know genes are involved in Alzheimer’s. There are two categories of genes that can play a role in determining whether a person develops a disease. Alzheimer genes have been found in both categories:
1) Risk genes increase the likelihood of developing a disease, but do not guarantee it will happen. Scientists have so far identified one Alzheimer risk gene called apoliprotein E-e4 (APOE-e4).
APOE-e4 is one of three common forms of the APOE gene; the others are APOE-e2 and APOE-e3. APOE provides the blueprint for one of the proteins that carries cholesterol in the bloodstream.
Everyone inherits a copy of some form of APOE from each parent. Those who inherit one copy of APOE-e4 have an increased risk of developing Alzheimer’s. Those who inherit two copies have an even higher risk, but not a certainty. Scientists do not yet know how APOE-e4 raises risk. In addition to raising risk, APOE-e4 may tend to make symptoms appear at a younger age than usual.
Experts believe there may be as many as a dozen other Alzheimer risk genes in addition to APOE-e4.
2) Deterministic genes directly cause a disease, guaranteeing that anyone who inherits them will develop the disorder. Scientists have found rare genes that directly cause Alzheimer’s in only a few hundred extended families worldwide.
When Alzheimer’s disease is caused by deterministic genes, it is called “familial Alzheimer’s disease,” and many family members in multiple generations are affected. True familial Alzheimer’s accounts for less than 5 percent of cases.
Genetic tests are available for both APOE-e4 and the rare genes that directly cause Alzheimer’s. However, health professionals do not currently recommend routine genetic testing for Alzheimer’s disease. Testing for APOE-e4 is sometimes included as a part of research studies.
Risk factors you may be able to influence
Age, family history and heredity are all risk factors we can’t change. Now, research is beginning to reveal clues about other risk factors we may be able to influence.
Head injury: There appears to be a strong link between serious head injury and future risk of Alzheimer’s. Protect your head by buckling your seat belt, wearing your helmet when participating in sports, and “fall-proofing” your home.
Heart-head connection: Some of the strongest evidence links brain health to heart health. Your brain is nourished by one of your body’s richest networks of blood vessels. Every heartbeat pumps about 20 to 25 percent of your blood to your head, where brain cells use at least 20 percent of the food and oxygen your blood carries.
The risk of developing Alzheimer’s or vascular dementia appears to be increased by many conditions that damage the heart or blood vessels. These include high blood pressure, heart disease, stroke, diabetes and high cholesterol. Work with your doctor to monitor your heart health and treat any problems that arise.
General healthy aging: Other lines of evidence suggest that strategies for overall healthy aging may help keep the brain healthy and may even offer some protection against developing Alzheimer’s or related diseases. Try to keep your weight within recommended guidelines, avoid tobacco and excess alcohol, stay socially connected, and exercise both your body and mind.
