MINNEAPOLIS - Why do some people stay sharp into their 90s, even if they have the amyloid plaques in the brain that are associated with Alzheimer's disease? And why do others reach their 90s without ever developing any plaques? These questions are explored in a new study published in the July 22, 2020, online issue of Neurology®, the medical journal of the American Academy of Neurology.
The study involved 100 people who did not have dementia and were followed for up to 14 years, when they were an average of 92 years old. The people had tests of their thinking and memory skills and imaging scans to see whether they had amyloid-beta plaques in their brains.
"With more and more people living into their 90s and even 100s, it's increasingly important that we be able to understand and predict the factors that help people preserve their thinking skills as they age and determine if there are any changes people can make during their younger years that can improve their chances of cognitive resilience," said study author Beth E. Snitz, PhD, of the University of Pittsburgh in Pennsylvania.
The researchers found that people who had normal scores on the thinking and memory tests at the start of the study were less likely to develop later problems with their thinking abilities, even if they had amyloid plaques in their brains.
"This finding is consistent with the theory that people with better lifelong thinking and memory skills have a 'cognitive reserve' that provides a buffer of protection against changes in the brain," Snitz said. "They can better compensate for any underlying brain changes."
They also found that people with the gene variant called APOE ε2, or apolipoprotein E ε2, which has been associated with a decreased risk of Alzheimer's disease, were more resistant to developing amyloid plaques than people who did not have that form of the gene.
People with the APOE ε2 gene version were six times less likely to develop plaques than people without the gene. Although protective, it is an uncommon version of the gene: only 10 out of 100 people in this study had it. Of those 10, seven people, or 70%, avoided plaques, compared to three people, or 30%, who did develop plaques.
Some modifiable lifestyle factors also played a role in successful brain aging. People who never smoked were more than 10 times more likely to maintain their thinking skills even with plaques than people who were smokers. People who had high scores on a blood pressure measure called pulse pressure were more likely to have a greater increase in plaques over time than people whose scores were lower. Pulse pressure is the systolic pressure, or the top number in a blood pressure reading, minus the diastolic, or the bottom number. Pulse pressure increases with age and is an index of the aging of the vascular system.
A limitation of the study was that participants were not randomly selected; they volunteered to take part over a long period of time and were mostly white people, highly educated and in overall good health. For these reasons, the results may not apply to other groups.
The study was funded by the National Institute on Aging and the National Institutes of Health.
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The American Academy of Neurology is the world's largest association of neurologists and neuroscience professionals, with over 36,000 members. The AAN is dedicated to promoting the highest quality patient-centered neurologic care. A neurologist is a doctor with specialized training in diagnosing, treating and managing disorders of the brain and nervous system such as Alzheimer's disease, stroke, migraine, multiple sclerosis, concussion, Parkinson's disease and epilepsy.
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