SAN DIEGO ― Super agers, the group of elderly people whose memory performance seems to defy aging, just produced another surprise for scientists: They can have numerous amyloid plaques in their brains, which is a hallmark of Alzheimer’s disease, yet their memory is unaffected. It’s as if they are somehow protected from the toxic effects of the plaques.
“It appears that some elderly individuals are immune to the effects of Alzheimer’s pathology,” said neurologist Changiz Geula, of Northwestern University Feinberg School of Medicine, who presented the findings Tuesday at the annual meeting of the Society for Neuroscience in San Diego.
Alzheimer’s disease is currently diagnosed based on a person’s symptoms, such as memory impairment. A definitive diagnosis can be made only after death, by looking at post-mortem brain tissue for signs of the plaques.
Geula and his colleagues examined the brains of eight people who died in their 90s and who had shown superior memory performance for their age. In nearly all healthy older individuals, some low level of plaques and tangles are present in areas of the brain. The brains examined in the study, however, showed a different pattern.
Three of the eight brains contained widespread distribution of the characteristic plaques and tangles of Alzheimer’s. Some other brains were very clean, not even showing the low amount of plaques that build up naturally with age, Geula said.
It’s not the first time that researchers find numerous plaques in the brains of cognitively healthy people. But the study provides a new level of evidence because it’s done in people who are the oldest of the old, George Perry, dean of the College of Sciences at the University of Texas, San Antonio, who wasn’t involved with the new research, told STAT.
The researchers then turned to examining the neurons in the brains of super agers, specifically in the hippocampus, the part of the brain that’s crucial for forming memories and is targeted by Alzheimer’s disease.
“We wanted to see what happens to neurons,” Geula said. “The striking feature here is that neurons seem to be substantially well preserved compared with Alzheimer’s disease brain with the same level of pathology.”
The findings raise numerous questions. Are the current approaches for diagnosing Alzheimer’s on point? Are some people protected from the toxic effects of plaques on their brain cells, and if so, how?
The team plans to do a thorough investigation of these brains to better understand what factors may be contributing to the protection of neurons in these individuals, Geula said.
Some of these factors could be environmental, and individuals can have control over them. Previous research has shown that people who engage in lifelong education are much more resistant to the effects of aging on the brain, a concept known as cognitive reserve. The idea is that working the brain keeps it stronger, and contributes to having more relationships among neurons, so the losses due to aging would have reduced effects.
Other factors could be genetic and involve certain cellular mechanisms that grant some people extra protection against plaques and tangles.
If future research finds what those mechanisms are, it could lead to two main beneficial outcomes, Geula said. “They can point to pathways that can be used to treat Alzheimer’s disease. Also, they can assist millions of normal individuals maintain their cognitive ability as they age.”