Published on: August 10, 2020
by National Institute on Aging:
Although it’s normal for brainpower to decline as people age, it’s not inevitable, studies show. Some people remain cognitively sharp into their 80s, 90s, and beyond, defying the common assumption that cognitive decline is a natural part of aging.
These lucky few, called cognitive super agers, perform demonstrably better on memory tests, such as remembering past events or recalling a list of words, compared with other adults their age. NIA-supported researchers are exploring the factors that set these people apart so the knowledge can be used to help others prevent or reverse age-related cognitive decline.
“There is a tendency to equate aging with a decline in mental function,” said Molly Wagster, Ph.D., chief of the Behavioral and Systems Neuroscience Branch in NIA’s Division of Neuroscience. “We want to study these cognitive super agers, who clearly break the expectation of cognitive decline, and unravel their secrets.”
How the Brain Changes with Age
“Atrophy is the strongest correlate of age,” said Claudia Kawas, M.D., of the University of California (UC), Irvine. She leads the longitudinal 90+ Study of more than 1,800 people age 90 years and older — the fastest growing sector of the U.S. population.
According to Kawas, a 90-year-old brain typically weighs 1,100 to 1,200 grams, and this is 100 or more grams less than the typical 40-year-old brain. Brain shrinkage mostly affects the prefrontal cortex and hippocampus, and the cerebral cortex, which is important for complex thought processes. Over time, the brain can also be affected by declining levels of neurotransmitters, changing hormones, deteriorating blood vessels, and impaired circulation of blood glucose. These brain changes can affect thinking, making it harder to recall words and names, focus on tasks, and process new information.
The Elite Brains of Cognitive Super Agers
Physically, the brains of cognitive super agers seem to defy wear and tear better than the average brain. Researchers at Northwestern University’s Mesulam Center for Cognitive Neurology and Alzheimer’s Disease in Chicago have tentatively identified a “brain signature” for cognitive super agers, which they define as people age 80 years and older who have performance on memory tests comparable to people two to three decades younger.
The researchers conducted magnetic resonance imaging (MRI) scans on 12 cognitive super agers, 10 cognitively normal peers, and 14 cognitively normal people in the 50- to 65-year age range. Comparisons revealed that the cingulate cortex, a brain region considered important for the integration of information related to memory, attention, cognitive control, and motivation was thicker in super agers than in their same-age peers and showed no atrophy compared with the same brain region of the middle agers. In fact, a specific region of the anterior cingulate cortex was significantly thicker in the brains of cognitive super agers than in middle agers’ brains.
In a separate study, the Northwestern researchers found that super agers’ brains contained a much higher density of a particular type of cell called von Economo neurons, which are linked to social intelligence and awareness. Their brains had more of these neurons even than the brains of younger adults.
In a third investigation, the Northwestern researchers used MRI to measure brain volume over an 18-month period in a small group of study participants age 80 and older. They measured a 2.24% average annual volume loss in the cognitively normal adults versus a 1.06% loss in the super agers. In short, the super agers’ brains shrank at a significantly slower rate.
At Massachusetts General Hospital, Boston, researchers are studying younger super agers — people between age 60 and 80 who have memory recall abilities similar to those of 18- to 32-year-olds. They’ve identified distinctive thicknesses in two neural networks that connect parts of the brain important to memory function. The thickness is nearly the same as in the brains of younger adults. The researchers also found that super agers have a bigger hippocampus than other adults their age.
Researchers with UC Irvine’s 90+ Study have identified a curious and counterintuitive feature of the super ager brain: sometimes it shows the pathologies that characterize Alzheimer’s disease and related dementias.
“Everyone thinks there’s this really strong correlation — if you have plaques and tangles, you have dementia, and if you don’t have plaques and tangles, you shouldn’t have dementia,” said Kawas. Through both autopsies and PET scans of the brains of the oldest old, investigators have found that “both of those things are often not true.”
Why Some People Retain Strong Brains into Old Age
Researchers are exploring several theories to explain why some people’s cognitive abilities stay intact to the end of life. Perhaps they start out in life with larger, stronger brains. Or perhaps their brains somehow change to compensate for aging’s damaging effects. Another theory being pursued is whether their brains have stronger defenses against the assaults of aging.
A person’s environment may be a factor. Human and animal studies by NIA-supported scientists have contributed to the growing body of evidence that enriching experiences, such as advanced education and mind-challenging occupations, can help brains last longer.
“Various exposures throughout the lifetime might help people maintain their brains better or maintain their cognition in the face of age- or disease-related brain changes,” explained Yaakov Stern, Ph.D., of the Taub Institute for Research on Alzheimer’s Disease and the Aging Brain at Columbia University Medical College, New York.
Other research focuses on genetic explanations. In an ongoing study of the Longevity Genes Project at Albert Einstein College of Medicine, New York, investigators are comparing the genetic profiles of children of healthy centenarians with the genetic profiles of the children of parents who did not live as long. They are looking for genes that might support strong neural networks and offer protection against mental and physical decline.
Social factors also could play a role in healthy cognitive aging. In one of Northwestern University’s studies, investigators gave a 42-item questionnaire on psychological well-being to 31 cognitive super agers and 19 cognitively normal peers. The cognitive super agers reported more friends and family connections, a finding that builds on past research showing links between psychological well-being and lower risk of Alzheimer’s.
Further research on cognitive super agers could lead to strategies that everyone can use — in younger years, in midlife, and in older age — to maintain thinking and memory skills. Just as important, it could also provide insights into how dementias such as Alzheimer’s might be prevented or reversed and provide critically important information for the identification of targets for interventions. And by identifying the factors that affect brain health, this research might one day be used to reduce disparities in brain-enriching opportunities so that everyone has a chance to keep their brain at maximum power throughout life.
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