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How Exercise May Help Protect Your Brain From Cognitive Decline and Dementia
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ByAmanda MacMillan
February 16, 2018
Older adults with poor fitness levels have more deterioration of white matter in their brains, according to a new study, compared with their fitter peers. White matter deterioration was also linked with a decline in decision-making brain function among adults with early signs of memory loss, suggesting that regular exercise may slow cognitive decline and perhaps even dementia, say the study authors.
The study, published in the Journal of Alzheimer's Disease, is not the first to suggest that exercise may help keep the brain healthy in old age. But while previous research has asked adults to self-report their fitness levels, the new paper used an objective test for cardiorespiratory fitness-measuring people's VO2 max, a measure of how much oxygen their lungs can utilize during intense exercise.
Abstract: Background: Mounting evidence showed the self-reported levels of physical activity are positively associated with white matter (WM) integrity and cognitive performance in normal adults and patients with mild cognitive impairment (MCI). However, the objective measure of cardiorespiratory fitness (CRF) was not used in these studies. Objective:To determine the associations of CRF measured by maximal oxygen uptake (VO2max) with WM fiber integrity and neurocognitive performance in older adults with MCI.
Methods:Eighty-one participants (age = 65±7 years, 43 women), including 26 cognitively normal older adults and 55 amnestic MCI patients, underwent VO2max test to measure CRF, diffusion tensor imaging (DTI) to assess WM fiber integrity, and neurocognitive assessment focused on memory and executive function. DTI data were analyzed by the tract-based spatial statistics and region-of-interest approach.
Results:Cognitively normal older adults and MCI patients were not different in global WM fiber integrity and VO2max. VO2max was associated positively with DTI metrics of fractional anisotropy in ∼54% WM fiber tracts, and negatively with mean and radial diffusivities in ∼46% and ∼56% of the WM fiber tracts. The associations of VO2max with DTI metrics remained statistically significant after adjustment of age, sex, body mass index, WM lesion burden, and MCI status. The DTI metrics obtained from the area that correlated to VO2max were associated with executive function performance in MCI patients. Conclusions:Higher levels of CRF are associated with better WM fiber integrity, which in turn is correlated with better executive function performance in MCI patients.
......The main findings from this study are that 1)VO2max, an objective assessment of CRF, is positivelycorrelated with WM fiber integrity in olderadults who have normal cognitive function or MCI;and 2) WMfiber integrity is also positively correlatedwith executive function, especially in MCI patients.These findings suggest that maintenance or improvementof CRF in older age may delay orslow cognitivedecline even in those who have high risk of AD.
Researchers from the UT Southwestern Medical Center recruited 55 older adults with mild cognitive impairment (MCI), meaning they were starting to show signs of memory problems, and 26 older adults with no signs of MCI. They used imaging techniques to study the white matter in participants' brains, and measured their VO2 max during a treadmill exercise.
They also performed a series of tests to evaluate people's executive function, which involves mental skills used for everyday decision-making, problem-solving and planning and executing tasks. Executive function is different from memory, but often, both skill sets suffer in people with age-related cognitive problems.
The researchers found that older adults with higher VO2 max scores-meaning they had better cardiorespiratory fitness-had less deterioration of the white-matter fibers in their brains. This was true in both groups of people in the study, with or without MCI, even after researchers controlled for factors such as age, sex and body mass index. White matter is comprised of millions of bundles of nerve fibers; it acts as the "computer cables" that connect various parts of the brain, says senior author Rong Zhang, neurology professor at UT Southwestern's O'Donnell Brain Institute. "If those cables get deteriorated, so do the pathways of communication," he says.
The researchers also found that, in adults with MCI, white matter integrity was associated with executive function. In other words, the healthier the white-matter fibers, the better people's scores were on tests for critical thinking and planning skills.
The findings strengthen the long-held hypothesis that maintaining or improving fitness levels in old age may protect the brain, the study authors write in their paper-even in people at high risk for Alzheimer's disease. "That's exciting, because the field right now is challenging," Zhang says. "Even though we suspect it, there hasn't really been any conclusive evidence that exercise can have an impact on the development of dementia." Last year, theNational Academies of Sciencesreported that, despite advances in understanding dementia, the evidence on treatment and prevention interventions "remains relatively limited and has significant shortcomings." The idea that increased physical activity may delay or slow age-related cognitive decline is supported by "encouraging but inconclusive evidence," the report concluded.
Many experts believe that maintaining physical fitness can help keep blood flowing normally to brain tissue, which can reduce the risk of damage or deterioration. Animal and human studies have also shown that aerobic exercise stimulates the release of growth hormones that may also improve brain function. In 2013, Zhang's team found that messages are more efficiently relayed between brain cells in older adults who exercise, compared to those who are sedentary.
Zhang says that the new study was too small to inform any definite conclusions, and that it does not answer questions about how much or what types of exercise might be best for older adults. Because it was observational, it was only able to show an association between fitness levels, white matter integrity and executive function-not a cause-and-effect relationship.
For those reasons, his team is now involved in an ongoingfive-year trialinvolving more than 600 older adults at high risk for Alzheimer's disease due to family history and other factors. The research, which is taking place at six medical schools around the country, aims to determine whether specific exercise routines-paired with medications to lower blood pressure and cholesterol-can reduce the risk of dementia.
"It makes sense that's what's good for the heart is good for the brain," says Zhang. "I don't think we need sophisticated science to make that point, but we do need more studies to make evidence-based recommendations about what strategies work best. And in a couple of years, I'm positive, we should have that sort of evidence."
What Type of Exercise Is Best for the Brain?
ByAlexandra Sifferlin
July 5, 2017
Exercise isjust as good for the brainas it is for the body, a growing body of research is showing. And one kind in particular-aerobic exercise-appears to be king. "Back in the day, the majority of exercise studies focused on the parts of the body from the neck down, like the heart and lungs," says Ozioma Okonkwo, assistant professor of medicine at the University of Wisconsin School of Medicine and Public Health. "But now we are finding that we need to go north, to the brain, to show the true benefits of a physically active lifestyle on an individual."
Exercise might be a simple way for people to cut down their risk for memory loss and Alzheimer's disease, even for those who are genetically at risk for the disease. In a Junestudypublished in theJournal of Alzheimer's Disease, Okonkwo followed 93 adults who had at least one parent with Alzheimer's disease, at least one gene linked to Alzheimer's, or both. People in the study who spent at least 68 minutes a day doing moderate physical activity had better glucose metabolism-which signals a healthy brain-compared to people who did less.
The brain benefits of exercise go beyond disease prevention. Okonkwo has also shown that people who exercise havegreater brain volumein areas of the brain associated with reasoning and executive function. "We've done aseries of studiesshowing that increased aerobic capacity boosts brain structure, function and cognition," he says, "Other people have found exercise canimprove mood." Okonkwo's research has also shown thatexercise can diminish the impact of brain changes on cognition, not just prevent it. "Exercise is the full package," he says. Exercise likely improves brain health through a variety of ways. It makes the heart beat faster, which increases blood flow to the brain. This blood delivers oxygen-a good thing, since the brain is the biggest consumer of oxygen in the body. Physical activity also increases levels ofbrain-derived neurotrophic factor(BDNF), which is known to help repair and protect brain cells from degeneration as well as help grow new brain cells and neurons, says Okonkwo.
In one study. Joe Northey, a PhD candidate at the University of Canberra Research Institute for Sport and Exercise in Australia, showed that when people ride a stationary bike, they experience increased blood flow to the brain, and within that blood are a range of growth factors that are responsible for cell growth and associated with improved brain function. "Considering exercise can also reduce the risks associated with common lifestyle diseases that impact the brain, such as high blood sugar and hypertension, it is further motivation to try to incorporate exercise as part of a healthy lifestyle," says Northey.
Aerobic exercise, likerunningandswimming, appears to be best for brain health. That's because it increases a person's heart rate, "which means the body pumps more blood to the brain," says Okonkwo. But strength training, likeweight lifting, may also bring benefits to the brain by increasing heart rate. The link between resistance training and better brain health is not as established, but research in the area is growing.
For now, Northey recommends a combination of the two. "Combining both is ideal," he says, for all of the other benefits exercise bestows on the body. "In addition to improving your brain function, you should expect to see improvements in cardiorespiratory fitness and muscle strength, as well as reducing the risk of obesity, diabetes and hypertension amongst other diseases."
The Simple Reason Exercise Enhances Your Brain
ByAlexandra Sifferlin
April 26, 2017
Evidence keeps mounting thatexerciseis good for the brain. It canlower a person's risk for Alzheimer's diseaseand may evenslow brain aging by about 10 years. Now, new research helps illuminate how, exactly, working out improves brain health.
In oneresearch review published in theBritish Journal of Sports Medicine, researchers examined 39 studies that looked at the link between exercise and cognitive abilities among people over age 50. They found thataerobic exerciseappears to improve a person's cognitive function andresistance trainingcan enhance a person's executive function and memory. Other exercises liketai chiwere also linked to improvements in cognition, though there wasn't as much available evidence. Ultimately, the researchers concluded that 45 minutes to an hour of moderate-to-vigorous exercise was good for the brain.
"There is now a wide body of research showing that the benefits to the body with exercise also exist for the brain," says study author Joe Northey, a PhD candidate at the University of Canberra Research Institute for Sport and Exercise in Australia. "When older adults undertake aerobic or resistance exercise, we see changes to the structure and function of areas of the brain responsible for complex mental tasks and memory function."
But how does exercise have these effects? Another new study presented at the American Physiological Society's annual meeting in Chicago explored one possible way. In the study, researchers from New Mexico Highlands University found that when people walk, the pressure of making impact with the ground sends waves through the arteries, which increase blood flow to the brain (also called cerebral blood flow). Getting enough blood to the brain is important for healthy brain function, since blood flow brings the brain oxygen and nutrients.
In the small study-which has not yet been published-researchers used ultrasounds to assess arteries and changes in cerebral blood flow in 12 healthy young adults while they were standing, walking and running. The increases in blood flow were greater when the men and women ran, but walking was enough to spur the effect. "[Increased cerebral blood flow] gives the brain more to work with," says study author Ernest R. Greene, a professor of engineering and biology at New Mexico Highlands University. "It's another positive aspect of exercise."
Scientists are still exploring multiple ways by which fitness improves the brain. But blood flow is a promising path, since it can also help create new brain cells. The protein BDNF (brain-derived neurotrophic factor) also seems to play a role because it helps repair and protect brain cells from degeneration.Exercise can also boost moodby triggering the release of feel-good hormones and chemicals, like endorphins, which can improve brain health. A 2015 study found thatexercise may be able to prevent the onset of depressive symptoms.
"Each type of exercise seems to have different effects on the growth factors responsible for the growth of new neurons and blood vessels in the brain," says Northey. "That may indicate why doing both aerobic and resistance training is of benefit to cognitive function."
Exercise Keeps the Brain Young: Study
ByAlexandra Sifferlin
December 29, 2016
Exercisecan combat cognitive decline, according to theresults of a new study. Older adults who did high amounts of moderate-to-vigorous physical activity had a 36% lower risk of cognitive impairment, as well as better memory and executive function, than those who did less.
In the study, published in the journalMedicine & Science in Sports & Exercise, researchers outfitted 6,400 people older than 65 years old with an activity tracker for a week. They also assessed people's cognitive abilities through a series of tasks. Three years later, the people who did moderate-to-vigorous levels of physical activity were significantly less likely to experience cognitive problems than those who were sedentary or did light physical activity.
The recent report adds to the scientific evidence that physical activity is linked to better brain health. Exercise has been shown toimprove blood flow to the brain, which can stimulate the growth of new blood vessels and cells; it has also been shown to lower a person's risk for chronic diseases like diabetes and obesity, which can take a toll on brain health over time. Another recent study found that exercisecan slow aging in the brainby 10 years.

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