What is Alzheimer's disease?

Alzheimer's disease is an incurable brain disease that was named after the German physician Alois Alzheimer, who identified it in 1907.

The disease, marked by a progressive degeneration of brain tissue, primarily affects people over the age of 65. In these cases, it's known as late-onset Alzheimer's disease. It has also been reported among people in their 50s, 40s and - rarely - 30s (early-onset Alzheimer's disease).

Nearly all people with Down syndrome will develop this disease if they live into their 40s.

Eventually, people suffering from Alzheimer's disease lose the ability to think, reason and co-ordinate movement and become incapacitated over the course of five to eight years. 

From the age of 60, your risk for developing Alzheimer's disease, or a related dementia, doubles every five years. At 60, the risk is approximately one in a hundred; by 65 years, it's one in 50; and by 70 years, it's one in 20. By the age of 85, approximately two out of every five people have some form of dementia.

The prevalence of Alzheimer's disease is closely linked to age and dramatically increases with age. Nearly 10% of all persons older than 65 have Alzheimer's disease and 50% of those older than 85 years also have it.

The average duration of the illness is six to eight years, but it can run its course in just a few months or take as long as 20 years.

In Australia, more than 320,000 people have been diagnosed with dementia. Of these people, 70% have Alzheimer's disease.