5 days ago
Some Human Brains Are Basically Defying Time by Refusing to Grow Old
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Some people's brains are so much younger than their chronological age, they could be hiding the secrets to treating dementia and other neurodegenerative diseases.
Known as 'superagers,' these individuals have brains that show physical aspects which are resistant to the causes of Alzheimer's and other conditions that cause memory loss.
While it is unknown whether superagers are born with larger brains or certain preconditions, future studies could reveal gene therapies and other treatments that could thwart diseases such as Alzheimer's.
Ask anyone what they dread about aging, and the thought of Alzheimer's and other forms of dementia is likely an answer high on the list. The irreversible symptoms of dementia only worsen with time and can become severe enough for the person to struggle remembering the faces of those close to them and even their own identity.
There is no cure for dementia (even though treatments that mitigate symptoms do exist). However, answers for prevention may lie in the brains of superagers, individuals over the age of 80 who have memories superior to others in their age group and can recall things as well as people decades younger. A Northwestern University study that spanned 25 years studied the lifestyles and brain activity of superagers both during life and in those who had donated their brains postmortem.
What the researchers at the Northwestern Alzheimer's Disease Research Center found were physical differences in brain structures that delayed symptoms of brain aging that often lead to dementia. Superagers would remember at least as many words from a list read to them as neurotypical adults who were 20 to 30 years younger. Their brain age of these subjects, mostly octogenarians and novogenerians, defied the expectations of the degenerative processes that often happen to the brains of people who reach their biological age. What is considered 'normal' brain aging involves decline. The average brain usually does not stay so remarkably intact.
'During the first 25 years of this program, we established that superagers constitute not only a neuropsychological but also a neurobiological phenotype distinctive from cognitively average age peers,' they said in a study recently published in Alzheimer's & Dementia.
What gives superagers these superpowers? There are several contributing factors. Somehow, their cerebral cortex resists thinning that is often a cause of neurodegenerative diseases. This outermost portion of the brain, also known as gray matter, is made of tightly packed neurons and responsible for higher-level processes that include memory, as well as learning, thought, reasoning, intelligence, language, decision-making, emotion, and personality. Superagers experience little to no cortical thinning, giving them cortical volumes similar to those of much younger brains.
There are also less obvious parts of the brain that give them an advantage, such as the cingulate gyrus, which is located below the cerebral cortex and above the corpus callosum. The cingulate gyrus also processes memory, along with emotion, self-regulation and pain. Superagers have a region in the cingulate gyrus that is thicker than the same region in younger adults. Their brains also show fewer signs that often indicate the onset of Alzheimer's, such as less plaque buildup.
Nerves and the neurons they are made of are another factor critical for brain health, especially in advanced age. Superagers were discovered to have larger entorhinal neurons, which are found in the entorhinal cortex and involved in memory of times, places and objects. Their cholinergic nerves, which are involved in memory and help control many physical processes, are especially well preserved. There is also a greater density of von Economo neurons, which speed up information processing, in their brains. Microglia, cells which are found in nerve fibers and often behind brain inflammation and lesions in older individuals, are less prone to causing inflammation in superagers.
Something that surprised the Northwestern research team was that superagers did not necessarily have many lifestyle parallels. Some took every measure to keep themselves healthy. Others had done just about everything that would seem to counter that, such as smoking, drinking, and being sedentary. Many suffered from stress and were not able to get adequate sleep. The one thing that most superagers did have in common was that they were had active social lives, making extracurricular activities a regular part of their lives. They even reported having more positive relationships with others than people around the same age who were cognitively average.
Eventually, the structure and function of superager brains may be the basis for preventative treatments and gene therapies targeting Alzheimer's, other dementias, and more neurodegenerative diseases such as Parkinson's. There are some aspects of this phenomenon that have yet to surface: whether superagers are born with larger brains, or with factors that make their brains almost immune to the ravages of time that cause others to experience the effects of brain degeneration. Either way, researchers are going to remember these findings for future studies.
'In the future, deeper characterization of the superaging phenotype may lead to interventions that enhance resistance and resilience to involutional changes considered part of average (i.e., 'normal') brain aging,' the researchers said. 'This line of work is helping to revise common misperceptions about the cognitive potential of senescence and has inspired [more] investigations.'
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