Aging brains are more vulnerable to Alzheimer’s disease because they lose the ability to quickly dispose of a waste protein, recent research found.
Researchers at Washington University School of Medicine in St. Louis identified some of the key changes in the aging brain that lead to greater risk of Alzheimer’s.
Why do we develop Alzheimer’s?
Aging is the greatest risk for Alzheimer’s. After age 65, the risk of developing the disease doubles every five years, and 40 percent of people 85 and older are estimated to be living with Alzheimer’s.
Researchers led Dr. Randall Bateman, senior author of the study and a neurologist at Washington University, found that, as people age, their brains can no longer quickly dispose of the protein amyloid beta 42. It is a key ingredient in the brain plaques that form as Alzheimer’s develop, a natural byproduct of brain activity.
Normally, it’s cleared from the brain before it can clump to form those plaques. But that changes over time.
“We found that people in their 30s typically take about four hours to clear half the amyloid beta 42 from the brain,” Bateman said in a university press release. “In this new study, we show that, at over 80 years old, it takes more than 10 hours.”
How plaque impacts our brains
The slowdown means the protein builds up in the brain, and has more time to clump and form plaques.
Researchers tested 100 volunteers ages 60 to 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 volunteers underwent detailed mental and physical evaluations, including brain scans. Researchers also checked their cerebrospinal fluid using technology developed by Bateman and study co-author Dr. David Holtzman, head of the neurology department at Washington University. The technology allowed researchers to monitor the body’s production and clearance of amyloid beta 42 and other proteins.
In patients who had developed brain plaques, amyloid beta 42 appears more likely to drop out of the fluid that bathes the brain and form plaques. Reduced clearance rates of the protein were associated with symptoms such as memory loss, dementia and personality changes ““ all clinical signs of Alzheimer’s.
Experts 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 and 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. “That may help us in our efforts to develop new treatments.”
The study appears in July’s online edition of the Annals of Neurology. It was funded in part through a grant from the National Institutes of Health.
