Today, nearly 20 percent of people age 65 or older suffer from mild cognitive impairment (MCI) and 10 percent have dementia. Those numbers seem destined to increase given our current large population of aging baby boomers, but early detection could, in theory, lead to more effective treatments-perhaps even prevention-of the Alzheimer's disease and other cognitive declines that threaten the elderly.
This week, a team of researchers at UCLA reports that a brain-scan technique can reliably track and predict cognitive decline over a two-year period. Their findings were published in the February issue of the Archives of Neurology.
The team created a chemical marker called FDDNP that binds to the amyloid protein plaques and tangles in the brain that are the hallmarks of Alzheimer's disease. The marker allows the protein deposits to be viewed using a positron emission tomography (PET) brain scan. The greater the "binding value," the greater the amount of the abnormal protein that is present in a particular brain region. Using evidence of greater binding, the researchers can pinpoint where in the brain abnormal protein deposits are accumulating.
For the study, researchers performed brain scans and cognitive assessments on 43 volunteers, average age 64, who did not have dementia at the beginning of the study. The participants were tested again two years later. At the start of the study, approximately half (22) of the participants had normal aging and the other half (21) had mild cognitive impairment, or MCI, a condition that increases the risk of developing Alzheimer's disease.
The researchers found that, for both groups, increases in binding in certain areas of the brain (see scan images) at the two-year follow-up correlated with the progression of cognitive decline. The areas most affected are known to be involved in decision-making, complex reasoning, memory, and emotions. Higher initial binding values in both subject groups were associated with a decline in cognitive functioning in areas such as language and attention at the two-year follow-up.
Of the 21 subjects with MCI, six were diagnosed with Alzheimer's at follow-up, and those six subjects had higher initial binding values than the other subjects in the MCI group. "We found that increases in FDDNP binding in key brain areas correlated with increases in clinical symptoms over time," said study author Dr. Jorge R. Barrio. "Initial binding levels were also predictive of future cognitive decline."
"We are finding that this may be a useful neuroimaging marker that can detect changes early, before symptoms appear, and it may be helpful in tracking changes in the brain over time," said study author Dr. Gary Small.
The researches are now using this brain-imaging technique in clinical trials to help assess promising therapies for brain aging. "Tracking the effectiveness of such treatments may help accelerate drug discovery efforts," said Small, the author of the new book The Alzheimer's Prevention Program. "Because FDDNP appears to predict who will develop dementia, it may be particularly useful in tracking the effectiveness of interventions designed to delay the onset of dementia symptoms and eventually prevent the disease."
For More Information:
Gary W. Small; Prabha Siddarth; Vladimir Kepe; Linda M. Ercoli; Alison C. Burggren; Susan Y. Bookheimer; Karen J. Miller; Jeanne Kim; Helen Lavretsky; S.-C. Huang; Jorge R. Barrio. "Prediction of Cognitive Decline by Positron Emission Tomography of Brain Amyloid and Tau." Arch Neurol. 2012;69(2):215-222.