Blood test could predict Alzheimer's chances

Researchers at UCSF say that a simple blood test seems to predict who will develop cognitive problems years before symptoms emerge, a finding they say could prove useful in treating diseases like Alzheimer's and might eventually help people stave off dementia.

A study of 997 elderly Americans, results of which were published Tuesday in the Journal of the American Medical Association, found that people with very low levels of a certain type of protein in their blood showed statistically significant cognitive declines over a nine-year period compared with people who had higher levels of the protein.

But people with more education or above-average literacy skills were less likely to show cognitive declines, even if they had low protein counts, perhaps indicating that exercising the mind late in life at least slows down symptoms of dementia, researchers said.

"Maybe you could do something about it by trying to use your brain and do cognitive activities or stimulation," said Dr. Kristine Yaffe, lead author of the study who is a psychiatry and neurology professor at UCSF and director of the Memory Disorders Clinic at San Francisco VA Medical Center. "It's not ready for prime time - there's not a definitive link, and we need to do trials - but it suggests something exciting."

For the time being, Yaffe said, there is no reason for people to get a blood test to predict their likelihood of developing Alzheimer's, primarily because there is no proven, effective treatment for the disease. But blood tests like the one Yaffe studied could help other researchers better understand Alzheimer's and how to treat it.

Seeking early signs

One reason scientists have struggled to find treatments is that by the time people are symptomatic, most of the brain damage has been done. Researchers have spent years trying to develop ways to diagnose Alzheimer's before symptoms show up.

"There's a lot of emphasis put on that because if you can identify the patients who will go on to develop dementia, then maybe you can identify treatments that can treat them better," said Dr. Marci Teresi, clinical lead of the Kaiser Permanente Santa Clara Memory Clinic. "We still don't have any treatments right now that are super promising."

Yaffe's study looked at a type of protein called amyloid beta, which is distinctive for the way it clumps up like plaque in the brains of Alzheimer's patients. The blood test looks for low levels of amyloid beta, suggesting that if the protein is building up in the brain, it's not circulating in the blood.

Study participants were on average about 74 years old, the blood test was done at the start of the trial, and they were given cognitive tests every year or two. Participants with the lowest level of protein in their blood showed an average drop on the tests of 6.59 points, on a 100-point scale, after nine years; participants with the highest level of protein showed an average drop of just 3.6 points.

When researchers looked at education and literacy levels, the cognitive declines were tempered somewhat. Participants who did not have a high school diploma and had the lowest protein levels dropped an average of 8.94 points, while those with at least a high school diploma and low protein levels lost an average of 4.6 points.

Exercising the mind

Yaffe said that correlation suggests that something known as "cognitive reserve" is at work. People who exercise their minds can potentially fight off, or work around, some of the damage done by the protein buildup in their brains.

It's not hard evidence, other researchers noted, although Yaffe's study is especially strong and backs up dozens of others that point to a tie between exercising the brain and preventing dementia. Certainly, it can't hurt to do word puzzles or take a class that stimulates the mind, no matter how old you are, said Dr. Adam Boxer, director of the Alzheimer's disease and frontotemporal dementia clinical trials program at UCSF's Memory and Aging Center.

"This study does provide some further support for improving mental function through mental exercises," Boxer said. "That's still really highly speculative. But, in general, we feel that anything you do to keep your brain sharp is going to help you."

E-mail Erin Allday at eallday@sfchronicle.com.

This article appeared on page A - 1 of the San Francisco Chronicle