A subtle change in a memory-making brain region seems to predict who will get Alzheimer's disease nine years before symptoms appear, scientists reported Sunday.
The finding is part of a wave of research aimed at early detection of the deadly dementia, and one day perhaps even preventing it.
Researchers scanned the brains of middle-aged and older people while they were still healthy.
They discovered that lower energy usage in a part of the brain called the hippocampus correctly signaled who would get Alzheimer's or a related memory impairment 85 percent of the time.
Still, the discovery may provide leads to scientists searching for therapies to at least delay the onset of the degenerative brain disease.
"It's exciting that we can even talk about prevention," said William Thies, scientific director of the Alzheimer's Association.
It is not clear if the men in the study became less social because Alzheimer's already was at work, but social activity is mentally stimulating.
A brain-healthy lifestyle aside, a big quest is to develop ways to identify Alzheimer's disease before symptoms emerge - finding biomarkers that could be targets for preventive therapies.
He measured blood levels of different types of beta amyloid, the sticky protein that makes up Alzheimer's hallmark brain plaques, in 565 people.
PET scans already can show Alzheimer's plaques in advanced disease.
The researchers found that the hippocampus was not as active as in people without that familial risk.
To prove if these early indicators are real, the National Institute on Aging, with financial help from the pharmaceutical industry and Alzheimer's Association, is beginning a $60 million study to scan the brains of 800 older Americans and try to pin down Alzheimer's earliest biological changes.