Superagers retain sharp minds into their 80s and beyond, defying the idea that cognitive decline is inevitable as we age. A 25-year study of these enviable few now reveals some of what's special about their underlying neurology.
"It's really what we've found in their brains that's been so earth-shattering for us," explains Northwestern University clinical neuropsychologist Sandra Weintraub.
Weintraub and colleagues found superagers' brains are oddly resistant to the buildup of Alzheimer's-related protein clumps and tangles. These individuals also have a higher concentration of one specific type of neuron in a critical region of their brain, and exhibit less inflammatory activity in their white matter compared to the general aging population.
Although the findings need to be validated in other populations, identifying a distinct neurobiological profile in superagers "opens the door to new interventions aimed at preserving brain health well into the later decades of life," says Weintraub.
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Superagers have memories beyond their 80s that rival those of people in their 50s. This study defines them as capable of remembering at least 9 words out of a list of 15 when tested, which is typical of people at least two to three decades younger. Some studies have found that less than five percent of the population can achieve a superager classification.
High extroversion is one trait superagers have in common with each other. Oddly, superagers aren't necessarily leading healthier lifestyles, with some smoking and drinking alcohol regularly; a factor that suggests a significant component of these folks' age-resisting superpowers is biological.
Weintraub and team monitored 290 people aged 80 and older since 2000 to compare those who would turn out to be superagers with those who age typically. Thanks also to generous donations of 79 superager brains, the researchers identified some key biological differences.
"What we realized is there are two mechanisms that lead someone to become a superager," says Weintraub. "One is resistance: they don't make the plaques and tangles [typically associated with Alzheimer's disease]. Two is resilience: they make them, but they don't do anything to their brains."
Cells that deliver information to the hippocampus, known as entorhinal neurons, were larger in superagers, possibly contributing to this resistance or resilience, the researchers suggest in their paper.
What's more, typically aging people had thinning in the outer brain layer, whereas superagers did not. This area of the brain governs our conscious thoughts, memory, and language.
Superagers also had more von Economo neurons and a thicker anterior cingulate gyrus, where these neurons are found, even compared to much younger people. This part of the brain is involved in regulating attention, emotion, and decision-making.
Previous studies already noted that this part of the brain isn't shrinking as expected in superagers. Weintraub and team suspect superagers are born with a higher density of von Economo neurons.
Together, these differences seem to keep superager brains quite stable compared to others over time.
"Many of the findings from this paper stem from the examination of brain specimens of generous, dedicated superagers who were followed for decades," says Northwestern University clinical neuropsychologist Tamar Gefen.
The team also noted a list of genes highlighted by prior research that still could be investigated for further insights.
Understanding the genes that affect cognition as we age may allow us to create pharmaceuticals that promote superager brain settings and resistance to Alzheimer's disease, the researchers conclude in their paper.
This research was published in Alzheimer's & Dementia.