Painless brain scans and simple blood tests may offer ways to predict who has the highest risk of Alzheimer's disease, and it may be possible to lower risks by drinking juice daily, researchers said.

The occasional alcoholic drink may also help, researchers told a prevention conference sponsored by the Alzheimer's Association.

"There is increasing evidence that we can do something for ourselves in terms of preventing this disease," Dr. Ron Peterson of the Mayo Clinic in Rochester, Minnesota, told a news conference.

It is important to act early, before symptoms such a memory loss begin, the researchers added.

The Alzheimer's Association estimates 4.5 million Americans have the incurable, fatal brain disease. It begins with mild memory loss and confusion and progresses gradually to a complete inability to care for oneself.

As many as 25 million people globally may have dementia, and those numbers will rise as the population ages.

"We need to be able to identify people at high risk as soon as possible," said Dr. Marilyn Alberts of Johns Hopkins University. Several studies presented on Sunday offered the possibility of predicting risk years before the disease develops.

Lisa Mosconi and colleagues at the New York University School of Medicine used positron emission tomography, or PET, scans to look at the brains of 53 normal elderly people.

They then watched for as long as 24 years to see who developed Alzheimer's. Nine did, while 19 developed mild cognitive impairment, which can worsen into Alzheimer's.

The PET scans detected reduced activity in an area of the brain called the hippocampus, which is known to be damaged in Alzheimer's. A 15- to 40-percent reduction in activity in the hippocampus, as measured by PET, predicted 85 percent of the Alzheimer's patients nine years in advance, Mosconi said.

It predicted 71 percent of the cognitive-impairment cases.

Alison Godbolt of the Institute of Neurology in London used a different brain scan called magnetic resonance spectroscopy in people who have a genetic flaw that makes them almost 100 percent certain to develop Alzheimer's, as well as people without the mutation.

The test looked for two compounds -- N-acetyl aspartate and myo-inositol and found their levels could predict which patients developed Alzheimer's.

VACCINE HOPES

Dr. Neil Graff-Radford of the Mayo Clinic in Jacksonville and colleagues found that blood levels of a protein called amyloid beta 42 plunged three to five years before a patient was diagnosed with Alzheimer's. This is presumably because the protein, which makes up the brain-clogging fibers associated with Alzheimer's, is staying in the brain instead of circulating in the blood, Graff-Radford said.

Companies are already targeting the protein with a vaccine in the hope of preventing Alzheimer's.

So far, drugs can temporarily slow Alzheimer's progression, but there is no cure. So experts are looking for ways to prevent it.

Amy Borenstein of the University of South Florida and colleagues found Japanese-Americans who drank the most fruit and vegetable juice had a fourfold lower risk of developing Alzheimer's than similar people who drank little or none.

Their study of 1,800 people covered 30 years.

Mark Sager of the University of Wisconsin and colleagues recruited people whose parents had Alzheimer's and found one clear way to predict who would also get the disease -- how much alcohol they drank.

He found that moderate drinkers had a lower risk of Alzheimer's than either non-drinkers or heavy drinkers.

"It is truly moderate intake that is protective," he said.