Australia will be the site of a world-first drug trail attempting to slow the onset of Alzheimer's disease by as much as a decade.

In what is being described as the "world's largest drug trail," Melbourne University has called on 600 healthy adults - who don't have any memory problems - aged 65 to 85 to volunteer for the first stage of the A4 study.

Early participants in the study will undertake a brain scan to determine if they have amyloid plaques, a sticky build-up which can accumulate on nerve cells around the brain.

Laureate Professor Colin Masters, from the University of Melbourne and the Florey Institute, said scientists believed the presence of amyloid plaques was a key reason some people developed Alzheimer's, a debilitating brain condition which affects memory.

"This is the first groundbreaking study to demonstrate whether we can delay onset by several years, at least five or 10 years," Masters, who will lead the Australian leg of the U.S.-based clinical test, told News Corp on Friday.

"This is the first attempt at stopping the disease before it starts and before it progresses to full blown dementia."

Only around 100 participants who show high levels of the substance will take part in the main study, which is set to begin returning results in 2020.

"In old age there appears to be a failure of machinery to get it out of the brain," Masters said. "This is the principal, underlying mechanism which causes the brain to degenerate."

Medical science has only been able to detect the presence of amyloid plaques in their early stages for the past few years.

"We can pick it up 10, 20 years before the onset of memory loss," Masters said.

"What we're trialling now is using an antibody and other drugs to help get (the amyloid) out of the brain."

The 100 study participants will be split into two groups, with half receiving a promising new anti-amyloid drug and the remainder a placebo.