BOSTON – For people with mild cognitive impairment, the rate of brain atrophy now may predict the level of cognitive decline years from now.
Every 1% increase in the rate of whole brain atrophy during a single year translated into 1.7-point decline on the Mini Mental State Examination (MMSE) score at 3 years, Kelvin Leung, Ph.D., said at the Alzheimer’s Association International Conference 2013.
"Many studies have shown associations between concurrent brain atrophy rates and cognitive decline, when compared and measured over the same time period," said Dr. Leung of the University College, London. "However, fewer have looked at the association between brain atrophy rates and future cognitive decline."
To examine that question, Dr. Leung used cognitive and imaging data from the Alzheimer’s Disease Neuroimaging Initiative. His study cohort included 471 patients (295 with mild cognitive impairment and 176 normal controls). The primary outcome was 36-month change on the MMSE. Secondary measures included changes in auditory verbal learning, immediate recall, category fluency, trail making, and backward digit span.
He used a magnetic resonance imaging measurement called boundary shift integral to calculate brain volume changes from baseline to 12 months. The boundary shift integral takes into account whole brain shrinkage, hippocampus shrinkage, and ventricle expansion to calculate a percentage difference from one time point to another.
When looking at the raw scores, every 1% increase in the 1-year brain atrophy rate was associated with a statistically significant 1.7-point decrease on the MMSE.
That atrophy rate also was significantly associated with a 2-point decline on the audio verbal learning test, a 2.8-point decline on the category fluency test, and an 11-point decline on the Trail Making Test A. The control subjects showed no significant cognitive changes.
Dr. Leung saw similar changes when he looked only at the change in hippocampal volume. For every 1% increase in the 1-year rate of hippocampal atrophy, patients with mild cognitive impairment experienced significant declines in the MMSE, audio verbal learning test, immediate memory, category fluency, and trail making. Again, control patients showed no changes.
There was a nearly identical correlation between ventricular volume expansion and the cognitive measures, he said.
The next step will be to investigate which specific cognitive changes are most associated with specific brain region changes.
Dr. Leung made no financial disclosures.