exercise brain

How exercise may protect against Alzheimer's

February 8, 2019

Science Daily/Columbia University Irving Medical Center

A hormone called irisin -- produced during exercise -- may protect neurons against Alzheimer's disease.

 

Athletes know a vigorous workout can release a flood of endorphins: "feel-good" hormones that boost mood. Now there's evidence that exercise produces another hormone that may improve memory and protect against Alzheimer's disease, according to a study co-led by Ottavio Arancio, MD, PhD, a researcher at Columbia University's Vagelos College of Physicians and Surgeons and Taub Institute for Research on Alzheimer's Disease and the Aging Brain.

 

The study was published in Nature Medicine.

 

Physical activity is known to improve memory, and studies suggest it may also reduce the risk of Alzheimer's disease. But researchers don't understand why.

 

A few years ago, exercise researchers discovered a hormone called irisin that is released into the circulation during physical activity. Initial studies suggested that irisin mainly played a role in energy metabolism. But newer research found that the hormone may also promote neuronal growth in the brain's hippocampus, a region critical for learning and memory.

 

"This raised the possibility that irisin may help explain why physical activity improves memory and seems to play a protective role in brain disorders such as Alzheimer's disease" says Arancio, who is a professor of pathology and cell biology and of medicine at Columbia University Vagelos College of Physicians and Surgeons.

 

Irisin is reduced in brains of people with Alzheimer's

 

In the new study, Arancio and his colleagues at the Federal University of Rio de Janeiro in Brazil and Queens University in Canada first looked for a link between irisin and Alzheimer's in people. Using tissue samples from brain banks, they found that irisin is present in the human hippocampus and that hippocampal levels of the hormone are reduced in individuals with Alzheimer's.

 

To explore what irisin does in the brain, the team turned to mice. These experiments show that irisin, in mice, protects the brain's synapses and the animals' memory: When irisin was disabled in the hippocampus of healthy mice, synapses and memory weakened. Similarly, boosting brain levels of irisin improved both measures of brain health.

 

Swimming boosts irisin, protects memory in mice

 

The researchers then looked at the effect of exercise on irisin and the brain. In the study's most compelling experiments, the researchers found that mice who swam nearly every day for five weeks did not develop memory impairment despite getting infusions of beta amyloid -- the neuron-clogging, memory-robbing protein implicated in Alzheimer's.

 

Blocking irisin with a drug completely eliminated the benefits of swimming, the researchers also found. Mice who swam and were treated with irisin-blocking substances performed no better on memory tests than sedentary animals after infusions with beta amyloid.

 

Together the findings suggest that irisin could be exploited to find a novel therapy for preventing or treating dementia in humans, Arancio says. His team is now searching for pharmaceutical compounds that can increase brain levels of the hormone or can mimic its action.

 

"In the meantime, I would certainly encourage everyone to exercise, to promote brain function and overall health," he said. "But that's not possible for many people, especially those with age-related conditions like heart disease, arthritis, or dementia. For those individuals, there's a particular need for drugs that can mimic the effects of irisin and protect synapses and prevent cognitive decline."

https://www.sciencedaily.com/releases/2019/02/190208173511.htm

Exercise linked to improved mental health, but more may not always be better

August 8, 2018

Science Daily/The Lancet

A study of 1.2 million people in the USA has found that people who exercise report having 1.5 fewer days of poor mental health a month, compared to people who do not exercise. The study found that team sports, cycling, aerobics and going to the gym are associated with the biggest reductions, according to the largest observational study of its kind.

 

More exercise was not always better, and the study found that exercising for 45 minutes three to five times a week was associated with the biggest benefits.

 

The study included all types of physical activity, ranging from childcare, housework, lawn-mowing and fishing to cycling, going to the gym, running and skiing.

 

Exercise reduces the risk of cardiovascular disease, stroke, diabetes, and mortality from all causes, but its association with mental health remains unclear.

 

Previous research into the effect of exercise on mental health has conflicting results. While some evidence suggests that exercise may improve mental health, the relationship could go both ways -- for example inactivity could be a symptom of and contributor to poor mental health, and being active could be a sign of or contribute to resilience. The authors note that their study cannot confirm cause and effect.

 

"Depression is the leading cause of disability worldwide, and there is an urgent need to find ways to improve mental health through population health campaigns," says Dr Adam Chekroud, Assistant Professor of Psychiatry at Yale University, and Chief Scientist at Spring Health, USA. "Exercise is associated with a lower mental health burden across people no matter their age, race, gender, household income and education level. Excitingly, the specifics of the regime, like the type, duration, and frequency, played an important role in this association. We are now using this to try and personalise exercise recommendations, and match people with a specific exercise regime that helps improve their mental health."

 

In the study, the authors used data from 1.2 million adults across all 50 US states who completed the Behavioural Risk Factor Surveillance System survey in 2011, 2013, and 2015. This included demographic data, as well as information about their physical health, mental health, and health behaviours. The study did not take mental health disorders into account, other than depression.

 

Participants were asked to estimate how many days in the past 30 days they would rate their mental health as 'not good' based on stress, depression and emotional problems. They were also asked how often they took part in exercise in the past 30 days outside of their regular job, as well as how many times a week or month they did this exercise and for how long.

 

All results were adjusted for age, race, gender, marital status, income, education level, employment status, BMI, self-reported physical health and previous diagnosis of depression.

 

On average, participants experienced 3.4 days of poor mental health each month.

 

Compared to people who reported doing no exercise, people who exercised reported 1.5 fewer days of poor mental health each month -- a reduction of 43.2% (2.0 days for people who exercised vs 3.4 days for people who did not exercise).

 

The reduction in number of poor mental health days was larger for people who had previously been diagnosed with depression, where exercise was associated with 3.75 fewer days of poor mental health compared with people who did not exercise -- equivalent to a 34.5% reduction (7.1 days for people who exercised vs 10.9 days for people who did not exercise).

 

Overall, there were 75 types of exercise recorded and these were grouped into eight categories -- aerobic and gym exercise, cycling, household, team sports, recreational activity, running and jogging, walking, and winter or water sports.

 

All types of exercise were associated with improved mental health, but the strongest associations for all participants were seen for team sports, cycling, aerobic and gym exercise (reduction in poor mental health days of 22.3%, 21.6%, and 20.1%, respectively).

 

Even completing household chores was associated with an improvement (reduction in poor mental health days of around 10%, or around half a day less each month).

 

The association between exercise and improved mental health (a 43.2% reduction in poor mental health) was larger than many modifiable social or demographic factors. For example, people with a college education had a 17.8% reduction in poor mental health days compared with people with no education, people with normal BMI had a 4% reduction compared with people who were obese, and people earning more than US$50,000 had a 17% reduction compared with people earning less than US$15,000.

 

How often and for how long people completed exercise was also an important factor. People who exercised between three and five times a week had better mental health than people who exercised less or more each week (associated with around 2.3 fewer days of poor mental health compared with people who exercised twice a month).

 

Exercising for 30-60 minutes was associated with the biggest reduction in poor mental health days (associated with around 2.1 fewer days of poor mental health compared with people who did not exercise). Small reductions were still seen for people who exercised more than 90 minutes a day, but exercising for more than three hours a day was associated with worse mental health than not exercising at all. The authors note that people doing extreme amounts of exercise might have obsessive characteristics which could place them at greater risk of poor mental health.

 

"Previously, people have believed that the more exercise you do, the better your mental health, but our study suggests that this is not the case. Doing exercise more than 23 times a month, or exercising for longer than 90 minute sessions is associated with worse mental health," continues Dr Chekroud.

 

"Our finding that team sports are associated with the lowest mental health burden may indicate that social activities promote resilience and reduce depression by reducing social withdrawal and isolation, giving social sports an edge over other kinds."

 

The study used people's self-reported assessment of their mental health and exercise levels so could be subject to bias. It also only asked participants about their main form of exercise so could underestimate the amount of exercise they do if they do more than one type.

 

Writing in a linked Comment, Dr Gary Cooney, Gartnavel Royal Hospital, UK, says: "There is gathering interest and momentum around research into exercise as a treatment for mental health disorders. The appeal is multifaceted: patients, particularly those reluctant to pursue medication or psychological approaches, are drawn to the self efficacy of exercise, the ability to attain a degree of agency in their own process of recovery. Mental health professionals, for their part, recognise the urgent need to address the comparatively poor physical health outcomes in the psychiatric patient population. With very high rates of physical comorbidity, and marked reductions in life expectancy, an intervention that might improve both mental and physical health is of particular clinical interest."

https://www.sciencedaily.com/releases/2018/08/180808193656.htm

Self-rated physical fitness in midlife an indicator of dementia risk

February 26, 2014

Science Daily/Suomen Akatemia (Academy of Finland)

How would you rate your own physical fitness? Is it good, satisfactory or maybe even poor? Surprisingly, your answer may reveal your future risk of getting dementia. A recent collaborative study from Finland, involving the follow-up of 3,559 adults for 30 years, has found that a simple question about self-rated physical fitness in midlife may reveal individuals who are at an increased risk of developing dementia. Those who reported poor self-rated physical fitness in midlife, at the mean age of 50 years, were four times more likely to get dementia during the next three decades compared to those with good self-rated physical fitness.

 

"Chronic conditions independently increase the dementia risk. Furthermore, if a person additionally feels that his or her physical fitness is poor, the risk is even higher. In terms of dementia prevention, maintaining good physical fitness seems to be especially important for people with chronic diseases," Kulmala says.

 

Poor self-rated fitness is known to be affected by lifestyle factors such as physical inactivity, poor mental wellbeing, lack of social connections, lower education, high body mass index and smoking. Perceived poor physical fitness therefore integrates several unfavourable aspects of lifestyle that have all been previously linked to increased dementia risk.

 

"The perception of poor physical fitness is most likely affected by different factors for different people. Therefore, I would encourage those who rate their fitness as poor to think about the factors behind this perception. Increasing physical and social activity, making better dietary choices or quitting smoking, for example, could change the rating into more positive. Individual choices that make you feel physically better may substantially decrease your future risk of developing dementia," Kulmala says.

http://www.sciencedaily.com/releases/2014/02/140226074825.htm

How Exercise Affects the Brain: Age and Genetics Play a Role

May 18, 2012

Science Daily/Dartmouth College

May 18, 2012

Science Daily/Dartmouth College

Exercise clears the mind. It gets the blood pumping and more oxygen is delivered to the brain. This is familiar territory, but Dartmouth's David Bucci thinks there is much more going on.

"In the last several years there have been data suggesting that neurobiological changes are happening -- [there are] very brain-specific mechanisms at work here," says Bucci, an associate professor in the Department of Psychological and Brain Sciences.

From his studies, Bucci and his collaborators have revealed important new findings:

  • The effects of exercise are different on memory as well as on the brain, depending on whether the exerciser is an adolescent or an adult.
  • A gene has been identified which seems to mediate the degree to which exercise has a beneficial effect. This has implications for the potential use of exercise as an intervention for mental illness.

Bucci began his pursuit of the link between exercise and memory with attention deficit hyperactivity disorder (ADHD), one of the most common childhood psychological disorders. Bucci is concerned that the treatment of choice seems to be medication.

"The notion of pumping children full of psycho-stimulants at an early age is troublesome," Bucci cautions. "We frankly don't know the long-term effects of administering drugs at an early age -- drugs that affect the brain -- so looking for alternative therapies is clearly important."

Anecdotal evidence from colleagues at the University of Vermont started Bucci down the track of ADHD. Based on observations of ADHD children in Vermont summer camps, athletes or team sports players were found to respond better to behavioral interventions than more sedentary children. While systematic empirical data is lacking, this association of exercise with a reduction of characteristic ADHD behaviors was persuasive enough for Bucci.

Coupled with his interest in learning and memory and their underlying brain functions, Bucci and teams of graduate and undergraduate students embarked upon a project of scientific inquiry, investigating the potential connection between exercise and brain function. They published papers documenting their results, with the most recent now available in the online version of the journal Neuroscience.

Bucci is quick to point out that "the teams of both graduate and undergraduates are responsible for all this work, certainly not just me." Michael Hopkins, a graduate student at the time, is first author on the papers.

Early on, laboratory rats that exhibit ADHD-like behavior demonstrated that exercise was able to reduce the extent of these behaviors. The researchers also found that exercise was more beneficial for female rats than males, similar to how it differentially affects male and female children with ADHD.

Moving forward, they investigated a mechanism through which exercise seems to improve learning and memory. This is "brain derived neurotrophic factor" (BDNF) and it is involved in growth of the developing brain. The degree of BDNF expression in exercising rats correlated positively with improved memory, and exercising as an adolescent had longer lasting effects compared to the same duration of exercise, but done as an adult.

"The implication is that exercising during development, as your brain is growing, is changing the brain in concert with normal developmental changes, resulting in your having more permanent wiring of the brain in support of things like learning and memory," says Bucci. "It seems important to [exercise] early in life."

Bucci's latest paper was a move to take the studies of exercise and memory in rats and apply them to humans. The subjects in this new study were Dartmouth undergraduates and individuals recruited from the Hanover community.

Bucci says that, "the really interesting finding was that, depending on the person's genotype for that trophic factor [BDNF], they either did or did not reap the benefits of exercise on learning and memory. This could mean that you may be able to predict which ADHD child, if we genotype them and look at their DNA, would respond to exercise as a treatment and which ones wouldn't."

Bucci concludes that the notion that exercise is good for health including mental health is not a huge surprise. "The interesting question in terms of mental health and cognitive function is how exercise affects mental function and the brain." This is the question Bucci, his colleagues, and students continue to pursue.http://www.sciencedaily.com/releases/2012/05/120518132812.htm

Brains evolved to need exercise

June 26, 2017

Science Daily/University of Arizona

Mounting scientific evidence shows that exercise is good not only for our bodies, but for our brains. Yet, exactly why physical activity benefits the brain is not well understood. Researchers suggest that the link between exercise and the brain is a product of our evolutionary history and our past as hunter-gatherers.

 

In a new article published in the journal Trends in Neurosciences, University of Arizona researchers suggest that the link between exercise and the brain is a product of our evolutionary history and our past as hunter-gatherers.

 

UA anthropologist David Raichlen and UA psychologist Gene Alexander, who together run a research program on exercise and the brain, propose an "adaptive capacity model" for understanding, from an evolutionary neuroscience perspective, how physical activity impacts brain structure and function.

 

Their argument: As humans transitioned from a relatively sedentary apelike existence to a more physically demanding hunter-gatherer lifestyle, starting around 2 million years ago, we began to engage in complex foraging tasks that were simultaneously physically and mentally demanding, and that may explain how physical activity and the brain came to be so connected.

 

"We think our physiology evolved to respond to those increases in physical activity levels, and those physiological adaptations go from your bones and your muscles, apparently all the way to your brain," said Raichlen, an associate professor in the UA School of Anthropology in the College of Social and Behavioral Sciences.

 

"It's very odd to think that moving your body should affect your brain in this way -- that exercise should have some beneficial impact on brain structure and function -- but if you start thinking about it from an evolutionary perspective, you can start to piece together why that system would adaptively respond to exercise challenges and stresses," he said.

 

Having this underlying understanding of the exercise-brain connection could help researchers come up with ways to enhance the benefits of exercise even further, and to develop effective interventions for age-related cognitive decline or even neurodegenerative diseases such as Alzheimer's.

 

Notably, the parts of the brain most taxed during a complex activity such as foraging -- areas that play a key role in memory and executive functions such as problem solving and planning -- are the same areas that seem to benefit from exercise in studies.

 

"Foraging is an incredibly complex cognitive behavior," Raichlen said. "You're moving on a landscape, you're using memory not only to know where to go but also to navigate your way back, you're paying attention to your surroundings. You're multitasking the entire time because you're making decisions while you're paying attention to the environment, while you are also monitoring your motor systems over complex terrain. Putting all that together creates a very complex multitasking effort."

 

The adaptive capacity model could help explain research findings such as those published by Raichlen and Alexander last year showing that runners' brains appear to be more connected than brains of non-runners.

 

The model also could help inform interventions for the cognitive decline that often accompanies aging -- in a period in life when physical activity levels tend to decline as well.

 

"What we're proposing is, if you're not sufficiently engaged in this kind of cognitively challenging aerobic activity, then this may be responsible for what we often see as healthy brain aging, where people start to show some diminished cognitive abilities," said Alexander, a UA professor of psychology, psychiatry, neuroscience and physiological sciences. "So the natural aging process might really be part of a reduced capacity in response to not being engaged enough."

 

Reduced capacity refers to what can happen in organ systems throughout the body when they are deprived of exercise.

 

"Our organ systems adapt to the stresses they undergo," said Raichlen, an avid runner and expert on running. "For example, if you engage in exercise, your cardiovascular system has to adapt to expand capacity, be it through enlarging your heart or increasing your vasculature, and that takes energy. So if you're not challenging it in that way -- if you're not engaging in aerobic exercise -- to save energy, your body simply reduces that capacity."

 

In the case of the brain, if it is not being stressed enough it may begin to atrophy. This may be especially concerning, considering how much more sedentary humans' lifestyles have become.

 

"Our evolutionary history suggests that we are, fundamentally, cognitively engaged endurance athletes, and that if we don't remain active we're going to have this loss of capacity in response to that," said Alexander, who studies brain aging and Alzheimer's disease as a member of the UA's Evelyn F. McKnight Brain Institute. "So there really may be a mismatch between our relatively sedentary lifestyles of today and how we evolved."

 

Alexander and Raichlen say future research should look at how different levels of exercise intensity, as well as different types of exercise, or exercise paired specifically with cognitive tasks, affect the brain.

 

For example, exercising in a novel environment that poses a new mental challenge, may prove to be especially beneficial, Raichlen said.

 

"Most of the research in this area puts people in a cognitively impoverished environment. They put people in a lab and have them run on a treadmill or exercise bike, and you don't really have to do as much, so it's possible that we're missing something by not increasing novelty," he said.

 

Alexander and Raichlen say they hope the adaptive capacity model will help advance research on exercise and the brain.

 

"This evolutionary neuroscience perspective is something that's been generally lacking in the field," Alexander said. "And we think this might be helpful to advance research and help develop some new specific hypotheses and ways to identify more universally effective interventions that could be helpful to everyone."

https://www.sciencedaily.com/releases/2017/06/170626155729.htm

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