Detecting Alzheimer’s Before Symptoms Appear
Researchers say an early diagnosis may be possible within five years.
Long before any doctor diagnoses the disease, most people who have Alzheimer’s have done something that is very out of character, embarrassing or even dangerous to themselves or others. The Alzheimer’s label rarely surprises family members or friends—rather; it just gives a name to the changes they have already been witnessing.
When will Alzheimer’s patients have the luxury of getting their diagnosis in the privacy of their doctor’s office, early enough so they can still comprehend the news in time to do something to stop the disease’s progress (assuming treatments become available)? Researchers who are developing the technology for early diagnosis predict that this may happen as soon as five years from now.
Here are a few examples of what the scientists are working on:
The wiring is fraying
Imaging studies suggest that Alzheimer’s may change the brain in distinct patterns. Those patterns show up in middle-age people who are still quite sharp mentally, but who have genetic risk factors for the disease, neurologist Charles D. Smith of the University of Kentucky Medical Center and colleagues report in the online journal Neurobiology of Aging.
With a type of magnetic resonance imaging (MRI) used primarily in research studies, researchers compared the brains of two groups of women. A high-risk group in their late 50s had both a family history of dementia as well as the apolipoprotein E4 allele (APOE4), a genetic variant that increases a person’s chances of getting Alzheimer’s. A comparison group in their late 60s had no extra risk factors. All of the women did fine on an extensive set of memory and intelligence tests.
The MRI assessed the brain’s white matter, which is made up of the fibers that connect one brain region to another. Myelin insulates these fibers, but that insulation thins as people age. Despite their normal cognitive abilities, the women carrying the genetic risk for Alzheimer’s had changes in these fibers that were not caused by aging and were similar to those seen in people with the disease.
Imagine “a computer cable composed of many different wires connecting many different areas of the brain–some of those wires’ or fibers’ insulating material, myelin, is getting worn before there are any symptoms,” explained Smith. Despite these changes, the fibers may function perfectly well up to a point, but then wear and tear takes its toll and the Alzheimer’s may “go public.” How quickly that happens appears to vary from individual to individual.
Following the path of destruction
Why not track Alzheimer’s as it makes its way through the brain’s memory center? A team of researchers has done just that, by comparing three-dimensional maps created over a few years of the brains of middle-aged people. At the start of the study, all of the participants aced their memory tests. But by the third year, some had developed mild cognitive impairment (MCI), a precursor to Alzheimer’s. The MCI group went on to develop Alzheimer’s, and the normal group remained healthy.
“This is the first longitudinal neuroimaging study of pre-clinical Alzheimer’s that maps this highly specific and orderly progression of disease-associated changes through the hippocampus,” reported neurologist Liana G. Apostolova of the Easton Center for Alzheimer’s Disease Research at University of California, Los Angeles and her colleagues, also in Neurobiology of Aging. By knowing where the disease strikes and when, researchers will be better able to discern if and how treatments are working.
Clear path to the brain
Having high blood pressure, being overweight or having high cholesterol is hard on your heart. However, these sins of modern times also increase the risk of developing Alzheimer’s disease, and they worsen age-related memory loss, studies suggest. So neuropsychologist Susan Bookheimer of the University of California, Los Angeles, School of Medicine, decided to get a picture of how the brain functions when facing these burdens.
In 2000, her team had showed that the brains of seniors with the APOE4 variant had to work harder to do as well as their peers on memory tests, as evidenced by greater blood flow in the regions responsible for retrieving memories from long-term storage, she explained.
Brookheimer and her colleagues then reported in October, 2008, that having systolic blood pressure (which is the higher number in a reading) or a body mass index (BMI) on the high side of normal may have a similar effect on the brain as the APOE4 gene does during memory tasks.
Among a group of 30 healthy, middle-aged adults, those with the highest (though still normal) blood pressure and BMI readings had the greatest amount of blood flow in the brain while performing memory tasks. The areas of the brain involved were the same as those seen in the 2000 study.
