"It is obvious that high levels of cortisol, a stress hormone, predict brain function, brain size, and cognitive test results," said Suda Shehshari, author of research and professor of neurology at the University Science Center. Health at the University of Texas at San Antonio.
"We have found that memory loss and brain shrinkage can be seen in relatively young people long before the symptoms are noticed," Sheshari said.
Too much to "fight or run"
Cortisol is one of the main hormones of stress, most notably known for its interference in the "fight or escape" instinct. When we are stressed or alert, the adrenal glands produce more cortisol. The hormone then stops various body functions that can affect survival.
Once the crisis has passed, cortisol levels have to fall and body systems have to go back to normal. But if your alert button is pressed, the body may continue to be damaged, causing anxiety, depression, heart disease, headache, weight gain, sleeping problems and, of course, memory and concentration problems.
According to experts, the brain is particularly vulnerable because it has the necessary nutrients to function properly.
"The brain is a very hungry organ," said Keith Fargo, director of Alzheimer's Association's research programs and association. "This requires a huge amount of nutrients and oxygen to keep working properly, so when the body needs these resources to cope with stress, there is less to be sent to the brain."
Intense stress is associated with memory loss
Previous studies have found a link between cortisol and the risk of developing dementia; however, the studies are aimed at the elderly and the brain area in which the memory is called hippocampus.
Among the benefits of the new study, according to Seshadri, is that a group of 48-year-old men and women were medically analyzed and MRIs were performed throughout the brain, not just the hippocampus.
Researchers have selected more than 2,000 people who have not shown signs of dementia and have applied several psychological tests to assess their cognitive abilities.
They were all part of the Framingham Heart Study, a long-term study sponsored by the United States National Heart, Lung and Blood Institute. The study has analyzed the health of the residents of Framingham, Massachusetts – and their children – since 1948.
The group was remeasured around eight years after the initial tests. Cross-corrected cortisol is measured before breakfast. Magnetic resonances are then performed, and the memory and cognition tests are repeated.
After adjusting the data by age, sex, body weight and smoking, it was found that people with the highest levels of cortisol had the greatest memory loss.
"I was not surprised by the change in knowledge," said Fargo, who was not involved in the study. "If you have a higher cortisol, you are probably stressed and probably will have more cognitive impairment."
Stress also affects the structure of the brain
Fargo noted that what was surprising was what was discovered about the effect of cortisol on the brain's structure.
High cortisol levels are associated with greater damage to parts of the brain that move information through the organ (radiant crown) and between the hemisphere (corpus callosum).
In addition, the study reveals that the part of the brain that is responsible for thinking, emotions, speech and muscle functions is less in people who have higher levels of cortisol.
The average brain volume of people who had high cortisol levels was 88.5% of the total brain volume, compared with 88.7% of those with normal cortisol levels.
"I was surprised that we could see such a big change in brain structure with elevated levels of cortisol compared to moderate levels of cortisol," Fargo said. "If you notice changes in middle-age brain structure, you can imagine what will happen when you are old enough to develop dementia."
Interestingly, the effects of increased cortisol on brain volume appear to occur only to women, not to men.
"Estrogen can increase cortisol," says Richard Isaacson, medical director of the Alzheimer's Clinic at the University of Wal-Cornell in the United States. "About 40% of women in the high cortisol group in the study are for hormone replacement therapy." Isaacon did not participate in the study.
Sheshari said corrections had been made to the study, which reported hormone replacement therapy. "This does not rule out the completely adverse effects of hormone replacement," he added, "but this is less likely in this story."
Sheshari also stressed that the results of the study show only a link rather than a cause, and that more research is needed to determine the relationship between elevated cortisol levels and dementia. He suggests that while this happens, people have to think about changes in their lifestyle to fight the stress of modernity.
Fargo agrees. "We know, for example, that people who exercise throughout their lives have a lower risk of developing dementia," he said. "Take time for yourself, meditate, there are always ways to control stress that will give you positive results."
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