Researchers at New York University said today they have come up with a new test to predict who will develop Alzheimer's disease, years before the first symptoms appear.
Because four million Americans have Alzheimer's, the test could help future victims and their families prepare, and could even minimize symptoms of the disease.
The basic test -- using electrodes and wires -- has been around for decades to diagnose seizures and tumors in the brain.
Now, using state-of-the-art software, researchers say the electroencephalograph, or EEG, can detect much more subtle changes that can be the first signs of Alzheimer's.
"It is our earliest warning system, we believe, that's telling us that dementia is a likely outcome in this individual for the next several years," Dr. Leslie Prichep of the New York University Medical School.
This pilot study tested people between 64 to 79 years of age with no evidence of memory loss. With millions of brain cells firing every second, the EEG measures the following:
Communication: how well cells in one side of the brain "talk" to those in another
Intensity: how much power or electrical current the cells are giving off
Frequency: the speed at which the cells are firing
The results published today found the EEG was 90 percent accurate in predicting Alzheimer's disease as much as a decade before symptoms appeared.
The test must now be studied on many more people to make sure it's as accurate as it appears. But the test raises the question of whether people really want to know if they are likely to develop a devastating disease for which there is no cure.
Some doctors say it could help victims and their families better prepare. There are also medications available to slow down symptoms of the disease, with more promising drugs in development.
"It's important to know who's at a particularly high risk, so when these therapeutics, drugs, and interventions are ready, we're able to intervene as soon as possible," said Dr. Ronald Petersen, a Mayo Clinic neurologist.
To make the Alzheimer's test easier to use and more widely available, researchers already are working on a hand-held EEG to one day make brain function a routine part of the annual physical.
ABC News' John McKenzie filed this report for "World News Tonight."