TUESDAY, Jan. 18 (HealthDay News) -- Researchers report promising results for a scanning test that aims to reveal the presence of Alzheimer's disease, potentially allowing doctors to try to treat the illness in its early stages. Another study finds that blood tests could indicate higher risks of dementia later in life.

But there's a catch: Alzheimer's disease is not curable, and existing treatments only have limited effects.

Even so, the ability to precisely diagnose Alzheimer's disease during life, which is now impossible, could lead to improved research, said memory specialist Dr. Anton P. Porsteinsson, a psychiatry professor at the University of Rochester School of Medicine, who was not involved with the studies.

The findings, published Jan. 19 in the Journal of the American Medical Association, "may have much more relevance" in the future, Porsteinsson said. "Basically, this is a step in the process."

Currently, doctors correctly diagnose Alzheimer's disease about 85 percent of the time, Porsteinsson said. The illness can be confirmed only through brain analysis after death. Even with existing scanning technology, "we can't see individual cells or what's going on," he said. "We can't see the functional impairment that happens," he added.

In one of the new studies, researchers led by a team from Avid Radiopharmaceuticals reported that they were able to find signs of Alzheimer's disease by using PET scanning technology. They had scanned 35 people who appeared to have the disease before their deaths and looked for signs of beta amyloid, a kind of gunk that clogs the brain in people with the illness.

The other study attempted to measure levels of beta amyloid in the blood. It linked lower levels -- a sign that the gunk is getting tied up in the brain -- to higher cognitive problems in 997 elderly people over a nine-year period.

The researchers also found that people with higher levels of "cognitive reserve" -- such as those with higher levels of education and literacy -- seemed to be buffered against dementia, said the study's lead author, Dr. Kristine Yaffe, a psychiatrist and professor at the University of California, San Francisco.

"The fascinating implication is that if you identify those at risk, maybe you could do something like cognitive stimulation to mitigate the risk," she said.

For now, though, "the markers reported here are far too unspecific to distinguish between people who will and will not get the disease," said Dr. Monique M.B. Breteler, an epidemiologist with University Medical Center Rotterdam in the Netherlands who wrote an accompanying commentary. "The importance of this paper is that it shows that there are detectable signals in blood that are related to the later development of the disease."

As for cost, Porsteinsson said the expense of the blood tests may go down. As to the other study, "the cost for the PET scans will always be pretty high because you've got to have such expensive tools."

More information

The U.S. National Institute on Aging has more on Alzheimer's disease.