A fitting boost for an aging brain

Joan Cohen

It’s widely recognized that exercise, done on a regular and continuing basis, is about the most powerful medicine we have to help us keep our bodies in shape: a defence against heart disease, stroke, diabetes and a host of other ailments.

Over recent years, a globe-spanning research effort has added an important new beneficiary to that list: the aging brain. Yes, the message goes, regular aerobic exercise – a brisk walk or a climb up flights of stairs – can help keep older people mentally fit.

Physical fitness is reflected in a person’s mental condition whatever their age, but for older people, whose brain can begin to show signs of decline around the time they enter their 60s, there is a special connection between the two.

As a multitude of clinical tests over the past decade have shown, the brains of people engaged in aerobic exercise can be seen to reverse the process of decline, and actually produce neuron cells – dispelling the long-held belief that mature brains could not grow new cells and thereby recover lost ground.

With that finding, scientists now acknowledge that truly fit bodies can ward off the seemingly normal process of mental decline – at least for a period of time. Many are hoping the growing body of findings connecting physical and mental fitness will prove a tipping point for people who aren’t yet making a serious effort to keep in shape.

With mental health issues, notably dementia, forecast to affect a sharply growing proportion of our population in coming years, at heavy over-all cost, the medical findings offer our society a reasonable prospect of a much brighter future on the health front.

Scientists tell us our bodies begin to show signs of aging about the time we reach age 40. Physically we slow down, and our brains, too, lose their edge. Around age 60, the shrinkage in our brains, averaging about one per cent a year, begins to manifest itself; signs of mental ineptitude begin to appear.

In solving problems or making decisions, we – most of us – don’t think as clearly in advanced years as we once did. Aerobic exercise – exercise that increases the intake of oxygen by the heart and lungs – is believed to result in a portion of this oxygen reaching the brain, helping bring it to a level of fitness where this mental decline is reversed.

Indeed, aerobic exercise can benefit all age groups in varying ways. But there are many ways of exercising and the brain has many parts: one can act on the other in many ways. Even looking solely at the aging population, scientists have many questions about the role exercise can play.

Do different kinds of exercise benefit different parts of the brain? Precisely what kind, or kinds, of exercise and in what way? for what reason? How much of that exercise is needed, and does the size of the dosage matter? Do any non-aerobic exercises (strength-training in the case of the elderly, for example) similarly affect thinking and/or memory?

Bit by bit, tests with people or animals are filling in some details.

  • It was a University of Illinois study that a few years ago surprised the science community by showing that people over 60 undertaking a program of aerobic exercise saw their brain volume increase. Researchers made the finding using magnetic resonance imaging on the volunteers to twice measure the volume of their brains’ hippocampus, the part of the brain that’s key to learning and memory.

A related United States study assigned 120 sedentary older people to either walk briskly for 40 minutes three days a week – considered “moderate” exercise – or else do stretching and toning exercises – in both cases for the period of a year. The results, published this year, revealed the hippocampus of the aerobic group had increased in volume by two per cent; the stretching group suffered the normal age-related one per cent decrease in volume.

Scientists say the medical community needs to define with some precision how much of a given exercise is needed to achieve a desired health benefit – so doctors can give their patients meaningful instructions. And, researchers have noted, the required duration for a specific exercise routine can vary, depending on whether a person is working out to increase their brain power or to help their heart.

  • University of Kansas lined up 101 volunteers, all healthy, aged 65 and older, divided them into four groups and had them all tested for their aerobic capacity an d how well they could remember and think.

Three of those groups were then assigned to walk briskly on a treadmill every week for 26 weeks for three different time periods. The first group exercised for a total of 75 minutes, the second for 150 minutes, the third for 250 minutes. The fourth group continued their normal lives and didn’t exercise. At the end of the period all four groups were again tested for their aerobic capacity, memory and cognitive ability

The result: the physical fitness of the three walking groups varied, rising to reflect the different time periods of their exercise. However, while each of the groups achieved improvements in their thinking processes, the level of improvement was about the same.

“A small dose of exercise” might be enough to improve many thought processes, said the doctor who co-directed the study, adding that scientists must find out in what ways- people are affected by different amounts of exercise.

  • A Finland study published early this year worked with a large number of male rats to find the type of exercise that would bulk up the animals’ mature brains with the highest number of new cells. Researchers injected a substance in the rats to mark the cells produced – and then put one set of rats to work jogging at moderate speeds on wheels in the cages; had another set climbing walls with weights on their tails and put a third group on treadmills for a stressful high intensity interval training regimen (alternating between high and relaxed speeds). The exercise sessions were repeated over a seven-week period.

The scientists found the aerobic runners, who had travelled long distances on their wheels, produced strikingly high numbers of new neurons,their output reflecting the distance they ran. The HIIT group, which had run harder, produced noticeably fewer neurons. The weight training rats had gained strength over the period but no new cells.

The upshot: a pronouncement by the research leader that “sustained aerobic exercise might be most beneficial for brain health also in humans,” and speculation that the distance running had produced a substance (brain-derived neurotrophic factor) that could work its magic on a human hippocampus as well.

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