Fonte: well.blogs.nytimes.com
At the age of 93, Olga Kotelko — one of the most successful and acclaimed nonagenarian track-and-field athletes in history — traveled to the University of Illinois to let scientists study her brain.
Ms. Kotelko held a number of world records and had won hundreds of gold medals in masters events. But she was of particular interest to the scientific community because she hadn’t begun serious athletic training until age 77. So scanning her brain could potentially show scientists what late-life exercise might do for brains.
Ms. Kotelko died last year at the age of 95, but the results of that summer brain scan were published last month in Neurocase.
And indeed, Ms. Kotelko’s brain looked quite different from those of other volunteers aged 90-plus who participated in the study, the scans showed. The white matter of her brain — the cells that connect neurons and help to transmit messages from one part of the brain to another — showed fewer abnormalities than the brains of other people her age. And her hippocampus, a portion of the brain involved in memory, was larger than that of similarly aged volunteers (although it was somewhat shrunken in comparison to the brains of volunteers decades younger than her).
Over all, her brain seemed younger than her age.
But because the scientists didn’t have a scan showing Ms. Kotelko’s brain before she began training, it’s impossible to know whether becoming an athlete late in life improved her brain’s health or whether her naturally healthy brain allowed her to become a stellar masters athlete.
And that distinction matters. Before scientists can recommend exercise to forestall cognitive decline, they need to establish that exercise does in fact slow cognitive decline.
So far, much of the available evidence has been weak. Many epidemiological studies show that physically active older people perform better on cognitive tests than their sedentary counterparts. But those studies were associational and leave many questions unanswered.
A new experiment by the same group of researchers who scanned Ms. Kotelko’s brain, however, bolsters the idea that exercise makes a difference in aging brains.
In the study, published last month in PLOS One, Agnieszka Burzynska, now an assistant professor of human development at Colorado State University in Fort Collins, and colleagues at the Beckman Institute for Advanced Science and Technology at the University of Illinois in Urbana scanned the brains of older men and women, aged 60 and 80, using a technique that tracks oxygen delivery to cells to determine brain activity. The researchers also measured their volunteers’ aerobic capacity and asked them to wear an activity monitor for a week to determine how much and how intensely they moved each day.
Notably, the most physically active elderly volunteers, according to their activity tracker data, had better oxygenation and healthier patterns of brain activity than the more sedentary volunteers — especially in parts of the brain, including the hippocampus, that are known to be involved in improved memory and cognition, and in connecting different brain areas to one another. Earlier brain scan experiments by Dr. Burzynska and her colleagues had established that similar brain activity in elderly people is associated with higher scores on cognitive tests.
Interestingly, as Dr. Burzynska points out, none of these volunteers were athletes, as Ms. Kotelko was. In fact, none of them formally exercised at all. But those who walked, gardened and simply moved more each day had brains that appeared to be in better shape than those of the other volunteers.
Of course, while this research offers tantalizing clues as to why exercise may be good for the brain, the study, like Ms. Kotelko’s scan, cannot prove cause and effect.
So, fundamentally, we still do not know whether and how physical activity changes our minds — a confusion that most likely was intensified for many of us by the results of a well-publicized study published last month in JAMA. In it, researchers from the Wake Forest School of Medicine in Winston-Salem, N.C., and other universities asked sedentary, elderly men and women, between the ages of 70 and 89, to start walking and doing light resistance training while other volunteers joined a health education program to serve as a control group.
To measure whether exercise made a difference in brain health, all of the participants completed cognitive testing at the beginning and the end of the study.
On the surface, the results were discouraging. The scores for the people in the exercise group were unchanged after two years and about the same as the scores for the group that attended health classes, intimating that exercise had had no effect.
But look deeper and there is another, intriguing inference. The cognitive performance of the volunteers in both groups remained stable, instead of declining, as might have been expected at their ages. So it may be that exercise did keep the volunteers’ minds sharp — and so did getting out and attending classes and engaging socially with the world.
“There are so many things that may impact brain aging,” Dr. Burzynska said, “and so much that we don’t yet understand about the process.”
Scientists need to scan people’s brains before and after long-term exercise programs, she said, and parse how exercise affects the many different varieties of thinking. In the JAMA study, for instance, there were some small improvements among the oldest exercising volunteers in their working memory and attention, but not other cognitive skills.
But even in advance of more studies, it “seems very likely,” Dr. Burzynska said, that exercise enables our brains to age better, even if, like Ms. Kotelko, we get started a little later in life.
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