Alzheimer's disease is a brain disorder named for German physician Alois Alzheimer, who first described it in 1906. It is the most common type of dementia. 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 progressive and fatal brain disease. Alzheimer's destroys brain cells, causing memory loss and problems with thinking and behaviour that is severe enough to affect work, learning skills and social life. Alzheimer's gets worse over time, and it is fatal.
It is the most common form of dementia. Dementia is a general term for memory loss, confusion and the loss of other intellectual abilities, serious enough to interfere with daily life. Alzheimer's disease accounts for 50 to 80 per cent of dementia cases. There are over 100 different types of dementia, the most common of which are: vascular dementia, mixed dementia, dementia with Lewy bodies and frontotemporal dementia.
There is no current cure. But treatments for symptoms, combined with the right services and support, can make life better for the thousands of people living with Alzheimer's. There is an accelerating worldwide effort under way to find better ways to treat the disease, delay its onset, or prevent it from developing.
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 with remembering certain things. However, serious memory loss, confusion and other major changes in the way our minds work are not a normal part of ageing - 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. In Alzheimer's disease, as in other types of dementia, increasing numbers of brain cells deteriorate and die.
The role of plaques and tangles
Two abnormal structures called plaques and tangles are prime suspects in damaging and killing nerve cells. Plaques and tangles were among the abnormalities that Dr. Alois Alzheimer saw in the brain of his patient Auguste D, although he called them different names.
Plaques build up between nerve cells. They contain deposits of a protein fragment called beta-amyloid (BAY-tuh AM-uh-loyd). Tangles are twisted fibres of another protein called tau (rhymes with 'wow').
Tangles form inside dying cells. Though most people develop some plaques and tangles as they age, those with Alzheimer's tend to develop far more. The plaques and tangles tend to form in a predictable pattern, beginning in areas important in learning and memory and then spreading to other regions.
Scientists are not absolutely sure what role plaques and tangles play in Alzheimer's disease. Most experts believe they somehow block communication among nerve cells and disrupt activities that cells need to survive.
Early-stage Alzheimer's disease
Early-stage is the early part of Alzheimer's disease when problems with memory, thinking and concentration may begin to become apparent to other family members or in a doctor's interview or medical tests. Individuals in the early-stage typically need minimal assistance with simple daily routines. At the time of a diagnosis, an individual is not necessarily in the early stage of the disease; he or she may have progressed beyond the early stage.
See our 'Progression of dementia' factsheet for further information