The researchers found that participants with mild cognitive impairment, who scored low on a memory recall test, and also had low glucose metabolism in particular brain regions, as detected through positron emission tomography (PET), had a 15-fold greater risk of developing Alzheimer's disease within two years.
"Not all people with mild cognitive impairment go on to develop Alzheimer's, so it would be extremely useful to be able to identify those who are at greater risk of converting using a clinical test or biological measurement," said the study's lead author, Susan Landau, a post-doctoral fellow at UC Berkeley's Helen Wills Neuroscience Institute and the Lawrence Berkeley National Laboratory.
"Researchers are trying to determine whether treating patients before severe symptoms appear will be more effective, and that requires better diagnostic tools than what is currently available," added William Jagust, a faculty member of UC Berkeley's Helen Wills Neuroscience Institute and principal investigator of the study.
During the study, the researchers compared a variety of measurements that had previously shown promise as early detectors of Alzheimer's.
The measurements included scores on the Auditory Verbal Learning Test; the volume of the hippocampus, the part of the brain associated with the formation of new memory; the presence of the apolipoprotein E4 gene, which has been linked to increased risk of Alzheimer's; certain proteins found in the cerebrospinal fluid; and glucose metabolism detected in PET brain scans.
A low rate of glucose metabolism in a particular brain region is considered a sign of poor neural function.
Although hippocampus volume and the cerebrospinal fluid markers showed promise in predicting disease progression, PET scans and memory recall ability were found to be the most consistent predictors.
The findings were presented at Alzheimer's Association 2009 International Conference on Alzheimer's Disease in Vienna, Austria.