Does Brain Size Matter in Clues to Alzheimer’s?


Does the size of our brain correlate with Alzheimer's disease? It very well may, according to a new study in this week's issue of Neurology that suggests the thickness of various parts of the brain could predict the onset of symptoms consistent with early Alzheimer's disease.

According to the Alzheimer's Association, more than 5 million Americans are living with Alzheimer's disease - a debilitating condition that affects memory thinking and behavior. This accounts for 50-80 percent of dementia cases in the elderly.

To determine whether the thickness of various regions of the brain might point to Alzheimer's risk, researchers embarked on a three-year study in which they looked at 159 individuals with an average age of 76 who were Alzheimer's-free at the beginning of the study. The researchers used brain imaging on these patients to assess the thickness of nine regions of the brain, chosen based on research that suggests these areas shrink in patients with Alzheimer's disease.

They found that 19 of them had enough shrinkage in these areas to qualify as high risk. A total of 116 were deemed to have average risk, and 24 were low risk.

The group was given memory and problem solving tests at the beginning of the study and over three years. The results of these tests showed that over 20 percent of the highest-risk individuals had scores consistent with cognitive decline, whereas there were only 7 percent in the average risk and 0 percent in the lowest risk group.

The researchers also found that 60 percent of the individuals at highest risk for Alzheimer's disease had abnormal levels of protein in the cerebrospinal fluid, another marker for Alzheimer's disease.

Study authors were hopeful that this approach could open up new avenues to detect Alzheimer's risk more quickly.

"This new streamline MRI technology is useful for screening people for silent Alzheimer's disease,  in hopes that we can target a segment of the population to enroll in large clinical trials for treatments as they become available," said  Dr. Bradford Dickerson, study author at Massachusetts General Hospital in Boston.

Dr. Susan Resnick of the National Institutes of Health, who wrote an accompanying editorial, noted that "The ability to identify cognitively normal individuals at higher risk for subsequent cognitive decline is an important step toward implementing and evaluating the new criteria for preclinical Alzheimer's disease."

Still, Dickerson cautioned that the research is preliminary and more work needs to be done.

"Further research is necessary to implement the use of these MRI biomarkers in combination with challenging cognitive tests as a screening tool to identify people at greatest risk" Dickerson said.