Memory loss and mental confusion are the first overt signs of Alzheimer's Disease, an incurable and fatal brain ailment.
But scientists are starting to find evidence of the disease long before symptoms appear. In the latest research, MRI scans show telltale signs in the brain a decade before memory and thinking are affected.
The pace of research aimed at understanding and preventing or treating Alzheimer's has been frustratingly slow.
A number of medicines have reached the market in recent years, but at best they only slow the progression of the disease.
Some researchers think that drugs may be more effective if they're given sooner, before symptoms become apparent.
A researcher at Harvard Medical School, Bradford Dickerson, is exploring an imaging technique that can identify characteristics of the brain that might signal the mental decline to come years later.
"So we wanted to test MRI, which is something that we think would potentially be more accessible to people if we end up needing to screen large groups of older subjects for these kinds of changes," Dickerson says.
In a new study, Dickerson and his colleagues studied a group of men and women starting when they were in their 70s. At the outset, they were given standard tests, and all of them showed normal memory and mental function. They also got an MRI scan of the brain.
Around 10 years later, the participants - now in their 80s - were again tested, and now about one out of four showed symptoms of Alzheimer's.
Going back to the MRI results from a decade or so earlier, the researchers found differences between the group who still had normal memory and those who were cognitively impaired, differences in Alzheimer's-related parts of the brain.
"And it turned out that those areas of the brain were, in subtle ways, smaller in the people who were cognitively normal but over the next eight years or so eventually developed Alzheimer's dementia than the same areas in the brains of people who remained cognitively normal over that period of time."
For now, this is just a research finding, but Dickerson sees a time in the not-too-distant future when doctors will tell people of a certain age with no symptoms that it's time to get tested for Alzheimer's.
"I believe that at some point in the next decade or so, we're going to see tests being proposed to be used as screening tools, sort of like colonoscopies are used," Dickerson says. "So that once you get past a certain age, you would undergo this screening test. And I think this MRI method has at least some plausibility to be one of those kinds of screening tools."
And the hope is that drugs in use now or yet to be developed will make a significant difference when taken before memory and mental function begin to decline.