April 7, 2011 -- Using MRI, researchers may be able to predict on an individual basis which people who have mild cognitive impairment will go on to develop Alzheimer's disease.
"We have known for a long time that the brain shrinks in Alzheimer's disease and you can detect this on MRI," says researcher Linda K. McEvoy, PhD, assistant professor of radiology at the University of California, San Diego School of Medicine.
The new study goes a step further. Researchers took into account brain changes over time and how closely they reflected typical patterns linked with a progression to Alzheimer's disease. From that, they produced a risk score for each person.
"From a brain MRI scan, we can provide information for individual patients who have mild cognitive impairment on their risk of developing Alzheimer's disease within the next year," McEvoy tells WebMD.
Alzheimer's disease affects about 5.4 million people in the U.S., according to the Alzheimer's Association.
McEvoy's study is published online and in the June issue of Radiology.
The new risk prediction tool must be tested in a more general population, McEvoy says. The tool is not ready for use outside research studies at this time, she tells WebMD.
Those who have mild cognitive impairment develop Alzheimer's at a rate of about 15% or 20% per year, McEvoy notes. It's much higher than in the general population, which develops Alzheimer's disease at a rate of about 1% or 2% per year for those who are 65 to 79, about 3% for people 80 to 84, and about 8% for those 85 and older.
Mild cognitive impairment involves problems with memory, language, or other mental functions. The problems are noticeable to others but do not yet interfere greatly with the person's daily life.
Researchers know that some people with mild cognitive impairment remain stable. Others have a gradual decline in thinking skills, while others decline rapidly.
Predicting the course for each individual has been difficult, however.
McEvoy and colleagues compared MRIs from 164 patients with Alzheimer's disease, 203 healthy patients, and 317 people who had mild cognitive impairment.
They used MRI exams from the Alzheimer's Disease Neuroimaging Initiative database. It includes MRIs performed between 2005 and 2010 on all three groups.
The aim of the initiative was to research the progression of mild cognitive impairment and early Alzheimer's.
McEvoy's team took into account what is known about brain changes in Alzheimer's, such as a loss of brain cells and a thinning of the cerebral cortex. The cerebral cortex plays a key role in memory, attention, thought, and language.
They observed the pattern of changes in each person. They also used a software program to compute a risk score for each person.