Australian scientists have identified a network of nine genes that play a key role in the onset of Alzheimer's Disease.

The discovery could help researchers develop new treatments to delay the onset of the chronic brain disease, which affects memory, orientation, mood and behavior.

Although the speed of progression can vary, the average life expectancy of an Alzheimer's sufferer following diagnosis is three to nine years.

Alzheimer's is said to affect up to 35 million people around the world and is predicted to affect one in 85 people globally by 2050.

Lead researcher, associate professor Mauricio Arcos-Burgos, from the Australian National University (ANU), said on Tuesday the breakthrough would hopefully have profound implications.

In their study of a family of 5,000 people in Colombia, South America, the ANU scientists were able to identify genes that delayed the disease, and others that accelerated it, and by how much.

"If you can work out how to decelerate the disease, then you can have a profound impact," said Arcos-Burgos, a medical geneticist at The John Curtin School of Medical Research (JCSMR) at ANU.

"I think it will be more successful to delay the onset of the disease than to prevent it completely. Even if we delay the onset by on average one year, that will mean nine million fewer people have the disease in 2050."

The Colombian family are afflicted by a type of hereditary Alzheimer's. They are a unique resource in the fight against the disease because they are such a large, close-knit family and live in a specific region in the western mountains of Columbia.

The United States National Institute of Health has put 125 million U.S. dollars towards developing treatments for Alzheimer's, which will be tested amongst this family.

Arcos-Burgos and his team took a different approach, studying the variable age of onset of dementia in this family, rather than trying to treat symptoms which develop later in life, even though changes in the brain can be observed in individuals before the age of 20.

With the cooperation of the family, the team were able to discount environmental factors and trace their genetic predisposition to Alzheimer's Disease back to a founder mutation in one individual who came to the region about 500 years ago.

The team was able to isolate the nine genes involved in Alzheimer's, some of which delay the onset by up to 17 years, while others advance its progress.

Arcos-Burgos said he was now turning closer to home, to study the genes of a group of people living in Queanbeyan, outside the Australian capital city of Canberra, who have been followed for the past 10 years.

The ANU study is published in the latest edition of Molecular Psychiatry.