Scientists in the US have managed to identify the point in the brain where Alzheimer's disease begins and believe the discovery will lead to much early diagnosis.
The team at the Columbia University in New York scanned the brains of 96 pensioners before tracking their health for the following 42 months.
At the start of the study, none of the volunteers had any issues with memory, but at its end 12 had developed Alzheimer's.
Of those people, each had shown reduced metabolic activity in the lateral entorhinal cortex (LEC) area of their brains.
Researchers believe that over time the effects of the cognitive condition spread from the LEC area to other parts of the cerebral cortex.
One area particularly vulnerable to the disease was the parietal cortex, which plays part in a person's spatial awareness and navigation.
Professor Scott Small from the university's Alzheimer's Disease Research Center said: "The LEC is considered to be a gateway to the hippocampus, which plays a key role in the consolidation of long-term memory, among other functions. If the LEC is affected, other aspects of the hippocampus will also be affected."
The team suspects that Alzheimer's has a "domino effect" on the brain with neurons in the LEC affecting the ability of neurons around them to fend off the condition.
Professor Karen Duff, who co-authored the study, said that the LEC is particular vulnerable to Alzheimer's because it is accumulates tangles of tau protein.
She believes the ability to pinpoint where the condition starts increases the chances of it becoming more treatable before it spreads to other brain regions.
To further test the study's findings, experiments have been conducted on lab mice with the same results being observed.
Alzheimer's disease is the most common kind of dementia in the UK and effects an estimated 496,000 people.