Scientists have identified nine new genes that appear to play a key role in the development of Alzheimer's disease.

The finding could help scientists develop new treatments to delay the onset of the disease, said lead researcher Mauricio Arcos-Burgos, an associate professor with the Australian National University.

"If you can work out how to decelerate the disease, then you can have a profound impact," said Arcos-Burgos, a medical geneticist.

"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."

For the study, scientists examined 5,000 people in Columbia to identify genes that delayed the disease, and others that accelerated it, and by how much.

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