Brains may start showing signs of Alzheimer's disease about a decade before the condition is recognized by doctors, a new study suggests.
Brain scans showing shrinkage in the cerebral cortex of seniors who later developed dementia suggested that researchers had found a marker for Alzheimer's.
Measurements of those areas "could be very important indicators to help identify who may be at risk of developing Alzheimer's dementia," study researcher Leyla deToledo-Morrell, said in a news release. "If a drug therapy or treatment is developed in the future, those who are still without symptoms but at great risk would benefit the most from treatment." DeToledo-Morrell is a professor in the department of neurological sciences at Rush University Medical Center in Chicago.
Participants, all of them in their 70s when the study began, had their brains scanned using magnetic resonance imaging (MRI), and the researchers measured the size of brain regions implicated in Alzheimer's disease. Those participants with the smaller measurements were three times more likely than the others to develop Alzheimer's within 10 years, the researchers concluded.
The findings suggest brain shrinkage in certain areas may be a marker for Alzheimer's disease. Because the study involved only 65 participants, however, more research would be needed before such a marker could be applied to the general population.
The participants were cognitively normal, with no symptoms of Alzheimer's disease, when the study began. They were followed for an average of nine years, undergoing tests to assess changes in their mental abilities.
By the end of the study, 15 participants had developed mental impairments, or dementia, characteristic of Alzheimer's disease (a condition that is officially diagnosed only by autopsy). These participants tended to show shrinkage in parts of the brain's cerebral cortex involved in Alzheimer's disease. The cerebral cortex is the outer layer of the brain, and parts of it are involved in thinking, remembering and planning, functions that are affected by Alzheimer's. In participants who developed Alzheimer's-associated dementia, this layer was thinner.
Participants were divided into three groups based on their cerebral cortex measurements. Among those with the smallest measurements, 55 percent developed Alzheimer's-associated dementia, compared with 20 percent in the group with medium-size measurements and none in the group with the largest measurements.
"This measure is potentially an important imaging marker of early changes in the brain associated with Alzheimer's disease that could help predict who might develop the dementia associated with this disease, and possibly even how long it would be before dementia develops," said study researcher Dr. Bradford Dickerson, of Harvard Medical School in Boston.
"It's a very interesting study," said Linda K. McEvoy, an assistant professor in the department of radiology at the University of California, San Diego School of Medicine, who was not involved in the study. "I think it shows the promise of quantitative MRI for early detection of Alzheimer's [brain degeneration,]" McEvoy said.
McEvoy notes that the study looked for a pattern of brain shrinkage across a number of brain areas. Including a large number of brain areas in analysis may increase the accuracy of such tests for early identification of Alzheimer's, she said.
"If you're actually seeing changes in a network of areas associated with Alzheimer's disease, then you might have more confidence that you're actually seeing changes associated with Alzheimer's," McEvoy said.
The findings are being published today (April 13) in the journal Neurology.
Pass it on: Areas of the brain involved in Alzheimer's disease may show signs of shrinkage up to 10 years before the disease symptoms appear.
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