WEDNESDAY, Feb. 8, 2006 (HealthDay News) -- Brain scans may one day help detect Alzheimer's disease and other forms of cognitive impairment before symptoms appear.
A new study has found a relationship between performance on certain cognitive and memory tests and certain differences in the brain.
"It's a very exiting study in the sense that it's probably the first time we've seen brain imaging evidence of this type from a normal population," said Maria Carrillo, director of medical and scientific affairs for the Alzheimer's Association.
"Clearly things are going on in the brain before people have symptoms of Alzheimer's," added study lead author Dr. William Jagust, professor of neuroscience and public health at the University of California, Berkeley. "The question is, how do we detect this?"
Finding a way to detect Alzheimer's disease early on, before symptoms start to appear, is one of the holy grails of Alzheimer's research.
"That's the goal, because we're hopeful that in the near future we'll be able to detect who's going to get it and have pharmaceutical drug interventions so we can stop them from getting it," Carrillo said.
Researchers have already used imaging to detect changes in the brains of people who have a genetic predisposition to Alzheimer's and in people with mild cognitive impairment, often a precursor to Alzheimer's. The problem is that many of these individuals already have symptoms, so the disease is not being picked up early enough.
Currently, there are only limited detection and treatment methods for Alzheimer's disease, which affects 4 million people in the United States -- a number that is expected to quadruple in the coming decades.
The new study, appearing in the Feb. 8 issue of the Annals of Neurology, looked at 60 cognitively normal older people. All the participants were part of SALSA, the first study of dementia and cognitive functioning in a Latino (mostly Mexican-American) population.
At the beginning of the study, the 60 participants underwent baseline PET and MRI brain scans along with a full battery of neuropsychological tests. They were followed for an average of 3.8 years, taking cognition and memory tests about once a year.
Over time, some people's performance declined on these cognition and memory tests, some stayed the same and some actually improved, Jagust said. Five people slipped from "normal older" to cognitive impairment, while one person developed Alzheimer's.
The researchers then cross-referenced these test scores with the PET and MRI results.
In the PET scans, people with lower blood sugar metabolism in the temporal and parietal cortex regions of the brain declined faster on the modified mini mental state examination (3MSE), a test that assesses global cognitive functions such as memory, language, spatial ability and judgment.
"This area is the same region that's involved in PET scans in people who have Alzheimer's, except this scan was done when they were normal," Jagust said. "What we're seeing is that the baseline PET scans in regions that we know are affected by Alzheimer's predict whether or not people are going to decline or how fast they are going to decline."
The story told by the MRI scans was similar: The smaller the entorhinal cortex and hippocampus regions of the brain in the scan, the more an individual's score declined on the delayed recall memory test. These regions appear to be the first affected as Alzheimer's develops. "What we're finding is a relationship between decline on the memory test and a brain region affected by Alzheimer's," Jagust said.
Although this study was done among Latinos, Carrillo saw "no reason why it can't be generalized."
Jagust is now involved in a study where scans are taken and then study participants are "tagged" as to how likely they appear to be to develop cognitive impairment and/or Alzheimer's. The researchers will then track these people over time to see if the scans have any predictive power.
"This leaves us with some optimism about predicting Alzheimer's in normal people," Jagust said. "There are a lot of different ways that people are trying to do this. We're working with brain imaging, others with memory testing, others with blood tests. We don't know which one will be the most effective, but the general sense is that something like this would be very helpful."
More information
To learn more, visit the Alzheimer's Association.
