Using an advanced MRI scan, researchers believe they have found changes in the chemistry of the brains of people with no cognitive problems that signal who is at future risk for Alzheimer's disease and other dementias.
And although there is no good treatment or cure for the disease, experts say finding ways to identify those at risk is essential when treatments and possibly a cure become available.
"We found biochemical changes that correlated with cognitive performance," said lead researcher Dr Kejal Kantarci, a radiologist at Mayo Clinic. "The better people did on tests that measure cognitive abilities, the fewer changes there were."
These biochemical changes were also associated with other changes in the brain that are markers for Alzheimer's disease, Kantarci said.
Kantarci said that people should not be looking at getting scans to detect these changes. "We are just at the early stages of identifying markers," she stressed.
However, finding these biomarkers is important, Kantarci added. "When possibilities for preventive intervention come about, then we will have a marker which will help us identify those individuals who would benefit from these preventive interventions," she said.
The report was published in the journal Neurology.
For the study, Kantarci's group used a technique called proton magnetic resonance spectroscopy to see if they could identify changes in brain chemistry in 311 men and women in their 70s and 80s who had no apparent cognitive problems.
The participants also underwent PET scans to see if there were any amyloid-beta deposits, or plaques, in the brain. These plaques are the first signs of Alzheimer's disease, the researchers noted.
In addition, participants took tests that evaluated memory, language and other skills.
Kantarci's team found that 33% of the people had significantly high levels of amyloid-beta deposits in their brains. These people also had high levels of two chemicals: myoinositol/creatine and choline/creatine.
Those with high levels of these so-called brain metabolites also were more likely to have lower scores on several of the cognitive tests, regardless of the amount of amyloid-beta deposits in their brains, the researchers added.
Kantarci said these biochemical changes start years before people show signs of cognitive problems. Whether these markers are a cause of dementia or only a signal for other changes isn't known, she said. "What we are seeing is a marker of a pathological process rather than a cause," she explained.
Heather M. Snyder, senior associate director of medical and scientific relations at the Alzheimer's Association, said "there is a growing body of evidence that biological changes associated with Alzheimer's disease are occurring maybe even 20 years prior to any individual having any cognitive issues."
"The goal is that we would like people to live a healthy life as long as possible, so if we can diagnose people with these changes as early as possible, when a treatment is available we can intervene - that's really our ultimate goal," she said.
That's why finding ways to identify people at risk early is important while the search for treatments and cures continues, Snyder said.
Identifying people at risk for dementia is also important for research, said Dr Marc L. Gordon, a neurologist and Alzheimer's researcher at The Feinstein Institute for Medical Research in Manhasset, N.Y.
"It is important to identify people at risk of dementia, particularly if we want to test therapies that have the potential to alter the process to try to prevent people from converting to dementia," he said.
Greg M. Cole, a neuroscientist at the Greater Los Angeles VA Healthcare System and associate director of the Alzheimer's Disease Research Center at the University of California Los Angeles David Geffen School of Medicine, said that "these results show that more and more specific biochemical changes that presage Alzheimer's disease can be detected in our normal ageing population using sophisticated imaging technology."
But, Cole added, "The question now is whether we can find a way to intervene in people where these very early steps in the disease process are measurable by suppressing the pathological process until we normalise the disease indices and show that they don't go on to develop dementia."
For more on Alzheimer's disease, visit the Alzheimer's Association.
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