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Most Alzheimer's drugs treat the symptoms of dementia. But, as this ScienCentral News video reports, a new tool may soon predict who will develop the disease even before symptoms occur.
Size Matters
Like it or not, our brains start shrinking at around age 40. But an accelerated type of brain shrinkage occurs in people who go on to develop Alzheimer's disease or other types of dementia. Now, research is revealing that the rate of brain volume loss may help identify those with mild cognitive impairment who are at risk for developing dementia.
"Mild cognitive impairment refers to people who are in a transition stage between normal cognition and being demented," explains Deniz Erten-Lyons, a neurologist at Oregon Health and Science University. "They have memory complaints, but these are not severe enough for clinicians to make a diagnosis of dementia. Dementia is a general word for people with problems in brain functions—memory problems, language problems—to a degree that it affects their ability to function in their day to day living."
Erten-Lyons says magnetic resonance imaging (MRI) brain scans may predict who will progress from mild cognitive impairment to full-fledged dementia. Her lab compared the scans of 55 volunteers over the span of 14 years; none of the subjects suffered from mild cognitive impairment at the beginning of the study. Each person was examined twice a year, given tests to place them into three categories: intact cognition, mild cognitive impairment that was considered stable, and mild cognitive impairment that progressed into Alzheimer's disease.
"We looked at the whole volume loss and the loss of brain cells overall in the whole brain as well as within different regions of the brain," says Erten-Lyons. "And we compared these shrinkage rates, how fast the whole brain and the different parts of the brain were shrinking between these groups."
Of the 55 participants, 18 didn't develop mild cognitive impairment and 37 did. Of that 37, 13 remained stable while the other 24 subjects progressed to Alzheimer's disease. Brain scans revealed that brain tissue shrinkage was faster for those who developed Alzheimer's disease than those with mild cognitive impairment. "People who had higher rates of brain shrinkage, whose brains were shrinking faster before the symptoms started and who were in the transition stages, were likelier to develop dementia compared to those in the transition stages," says Erten-Lyons. "Those who get actually get dementia faster do have faster rates of brain shrinkage even before they have symptoms, which means that whatever is going on in the brain in Alzheimer's disease actually starts way before you show any symptoms."
Erten-Lyons points out that not all people with mild cognitive impairment go on to develop Alzheimer's disease. "We know that they a much higher risk of developing Alzheimer's disease, but we also know that some people in these transitional stages can flip back to going back to normal," she says. "This is what we're trying to figure out: What is it that makes these certain people stay at these transitional stages for longer periods of time, and can we actually treat them while they are in this stage and prevent them from entering Alzheimer's disease."
Still, Erten-Lyons stresses that there is no cure for Alzheimer's disease yet. "Alzheimer's disease is not like a cancer, where if you detect it presymptomatically, you'll take it out and it will be gone and you’ll be cured," she says. "We don't have any treatments available yet."
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