As we age, our brains are less able to clear amyloid beta 42, a main ingredient of Alzheimer’s brain plaques, according to new research.
“We found that people in their 30s typically take about four hours to clear half the amyloid beta 42 from the brain,” said senior author Randall J. Bateman, M.D., a professor of neurology at Washington University School of Medicine in St. Louis. “In this new study, we show that at over 80 years old, it takes more than 10 hours.”
This slowdown results in rising levels of amyloid beta 42 in the brain, which increase the chances that it will clump together to form Alzheimer’s plaques, according to the researchers.
For the study, the researchers tested 100 volunteers between the ages of 60 and 87. Half had clinical signs of Alzheimer’s disease, such as memory problems. Plaques had begun to form in the brains of 62 participants, the researchers report.
The volunteers were given detailed mental and physical evaluations, including brain scans to check for the presence of plaques. The researchers also examined the volunteers’ cerebrospinal fluids using a technology developed by Bateman and co-author David Holtzman, M.D., head of the Department of Neurology at Washington University.
The technology, known as stable isotope-linked kinetics (SILK), allows the researchers to monitor the body’s production and clearance of amyloid beta 42 and other proteins.
In volunteers with evidence of plaques, the researchers observed that amyloid beta 42 appears to be more likely to drop out of the fluid that bathes the brain and clump together into plaques. Reduced clearance rates of amyloid beta 42, such as those seen in older participants, were associated with clinical symptoms of Alzheimer’s disease, such as memory loss, dementia, and personality changes, according to the study’s findings.
Scientists believe the brain disposes of amyloid beta in four ways: By moving it into the spine, pushing it across the blood-brain barrier, breaking it down or absorbing it with other proteins, or depositing it into plaques.
“Through additional studies like this, we’re hoping to identify which of the first three channels for amyloid beta disposal are slowing down as the brain ages,” Bateman said. “That may help us in our efforts to develop new treatments.”
The study was published in the Annals of Neurology.