Our bodies replace old cells all the time. The adult body creates new neurons inside the hippocampus to function correctly. Superagers — people who remain mentally sharp and clear into their 80s and 90s — produce about twice the number of brain cells as their healthy peers. People with Alzheimer’s had fewer.
“Superagers are required to have outstanding episodic memory — the ability to recall everyday events and past personal experiences,” said Emily Rogalski, a professor of neurology at the Univ. of Chicago. “It’s important to point out when we compare the Superagers to the average agers, they have similar levels of IQ, so the differences we’re seeing are not just due to intelligence.”
Superagers share some traits. They are generally positive thinkers who enjoy a challenge and tend to be lifelong learners who read. Many work into their 80s and are social butterflies with active lives and volunteering schedules. However, their physical health varies. They don’t necessarily eat healthily or exercise, and some have metabolic concerns, heart disease or other ailments.
Researchers looked at 38 brains that were donated to science for the study. There were eight healthy young adults between the ages of 20 and 40. There were eight healthy older people between 60 and 93. They also had six superagers between 86 and 100. For the less healthy group, they had six individuals with preclinical Alzheimer's pathology, aged between 80 and 94. Finally, there were 10 individuals with an Alzheimer's diagnosis, aged between 70 and 93.
“This is a big step forward in understanding how the human brain processes cognition, forms memories, and ages,” said neuroscientist Orly Lazarov of the Univ. of Illinois Chicago. “Determining why some brains age more healthily than others can help researchers make therapeutics for healthy aging, cognitive resilience, and the prevention of Alzheimer’s disease and related dementia.”
As recently as 1998, scientists thought we were born with all our brain cells. They thought that what you had at birth was what you had for life. But a study found that the hippocampus, where memories are made, makes more neurons throughout life. More recent studies have found that the brains of people with Alzheimer’s appear to struggle to make new neurons.
This study saw that the brains in the preclinical Alzheimer’s group had molecular changes that suggested their ability to grow neurons was failing. And the brains in the Alzheimer’s group had an obvious lack of young neurons. Genetic analysis of the superager’s neural cells’ nuclei showed that they had higher plasticity, more suited to survive and grow stronger synaptic connections, and more.
“We’ve always said that superagers show that the aging brain can be biologically active, adaptable, flexible, but we didn’t know why,” said neuropsychiatrist Tamar Gefen of Northwestern Univ. “This is biological proof that their brains are more plastic, and a real discovery that shows that neurogenesis of young neurons in the hippocampus may be a contributing factor.”
“What’s emerging from this study is this idea that SuperAgers are, in general, very distinct,” said co-author Dr. Changiz Geula, research professor at the Mesulam Institute. “The genetic programs that support brain cell survival and communication stay on in SuperAgers in these cells, but they’re switched off in Alzheimer’s disease.”
