Brain Size May Predict Risk for Early Alzheimer's

Among individuals who don’t currently have memory problems, those with smaller regions of the brain’s cortex may be more likely to develop symptoms consistent with very early Alzheimer’s disease, according to research published online in Neurology on December 21, 2011.

“The ability to identify people who are not showing memory problems and other symptoms but may be at a higher risk for cognitive decline is a very important step toward developing new ways for doctors to detect Alzheimer’s disease,” said Susan Resnick, PhD, with the National Institute on Aging in Baltimore, who wrote an accompanying editorial.

For the study, researchers used brain scans to measure the thickness of regions of the brain’s cortex in 159 individuals around the age of 76 who did not have dementia. The brain regions were chosen based on prior studies showing that they shrink in patients with Alzheimer’s dementia.

Of the 159 people, 19 were classified as at high risk for having early Alzheimer’s disease due to smaller size of particular regions known to be vulnerable to Alzheimer’s in the brain’s cortex, 116 were classified as average risk and 24 as low risk. At the beginning of the study and over the next 3 years, participants were also given tests that measured memory, problem solving, and ability to plan and pay attention.

The study found that 21% of those at high risk experienced cognitive decline during three years of follow-up after the MRI scan, compared to seven percent of those at average risk and none of those at low risk.

“Further research is needed on how using MRI scans to measure the size of different brain regions in combination with other tests may help identify people at the greatest risk of developing early Alzheimer’s as early as possible,” said study author Bradford Dickerson, MD, of Massachusetts General Hospital in Boston, in a statement.

The study also found 60% of the group considered most at risk for early Alzheimer’s disease had abnormal levels of proteins associated with the disease in cerebrospinal fluid, which is another marker for the disease, compared to 36% of those at average risk and 19% of those at low risk.