New diagnostic guidelines for research purposes being proposed by the National Institute on Aging and the Alzheimer’s Association call for early biomarkers of risk, analogous to high cholesterol levels) that predict who is likely to get it. These include scans for amyloid plaque in the brain, a unique feature of Alzheimer’s, and tests of cerebrospinal fluid.

Researchers agree that Alzheimer’s smolders in the brain a decade or more before memory loss or diminished ability to reason. With new criteria for early diagnosis, the stage is set for testing drugs that might prevent the disease from running its course, investigators say.

The biggest questions are what it means when tests find that people have amyloid in their brain yet have no symptoms. Are those people certain to develop Alzheimer’s if they live long enough? Or is brain plaque like the very different plaque that forms in arteries? Many people have plaque in their arteries yet never have a heart attack.

If amyloid plaque is analogous to artery plaque, some who take drugs would be protected from Alzheimer’s. But many others who would never get Alzheimer’s might end up taking drugs for decades. That means the drugs must be very safe and not prohibitively expensive.