After the age of 65, the risk of developing Alzheimer's disease doubles every five years, and new research may have pinpointed some key changes in the brain that cause this to happen.
A team of researchers determined changes associates with the amyloid beta 42 protein, which is believed to be the "primary driver" of Alzheimer's disease, Washington University School of Medicine in St. Louis reported.
"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, the Charles F. and Joanne Knight Distinguished Professor of Neurology. "In this new study, we show that at over 80 years old, it takes more than 10 hours."
The slowdown in clearance rates leads to elevated levels of amyloid beta 42 in the brain, increasing the risk of the protein clumping together and forming Alzheimer's plaques.
To make their findings the researchers looked at 100 volunteers between the ages of 60 and 87, half of which had clinical signs of Alzheimer's disease and 67 of which had begun to form Alzheimer's plaques. The participants underwent mental and physical evaluations including brain scans and cerebrospinal fluid analyses. The researchers used technology called stable isotope-linked kinetics (SILK) to evaluate the body's production and clearance of amyloid beta 42.
The study revealed that in patients with signs of Alzheimer's plaques, amyloid beta 42 tended to be more likely to fall from the brain fluid and clump together. Clearance rates of amyloid beta 42 was linked to clinical symptoms of Alzheimer's disease, such as memory loss and personality changes. Researchers believe the key protein is disposed of 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," the researchers reported.
"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 findings were reported in a recent edition of the journal Annals of Neurology.
