Our clients are usually aware of the exercise benefits on cardiovascular health but are surprised to hear that exercise can improve your brain health and reduce your likelihood of developing dementia.

This resource has been put together for clients who want to know more about how this works on a cellular level. Much of the information has been taken from the publication“Physical Activity For Brain Health and Fighting Dementia”, in which Alzheimer’s Australia makes a convincing argument that dementia prevention should be added to the list of diseases that can be prevented or delayed with cardiovascular exercise.

We like to think of this as doing our bit in leading the horse to water…

Introducing neurons, synapses and neuroplasticity

Neurons are the cells in the brain that are responsible for your brain’s functioning.

There are approximately 1000 billion neurons in the adult human brain.

Neurons, like your skin cells, can die off, and new neurons can grow.

New neuron growth is called neurogenesis. Neurogenesis slows down with age.

Synapses are the communication channels that connect neurons so that they can speak to each other. New synapses are formed when we learn something new.

The brain is adaptive. When the brain is damaged by injury or disease, it can re-wire itself to an extent. It does this by building new neurons and new synapse connections. This adaptive response is called neuroplasticity, and it explains how we can train people to improve the way they function after brain injury or stroke, for example.

Neuroplasticity is not only available to us when we have to adapt to injury or brain damage. Neuroplasticity is what helps us learn to adapt to new environments or new information. Neuroplasticity is something everyone can tap in to if we want to optimize the function of our brains.

How does-dementia differ from normal ageing?

When the brain ages, it shrinks slightly, and this is called atrophy. Atrophy occurs because there is some natural loss of some neurons and synapses as neurogenesis slows down. This loss of neurons and synapses, and subsequent atrophy, is far more pronounced in Alzheimer’s disease.

In dementia, more neurons and synapses appear to be damaged and die off at a faster rate than is expected with normal ageing.

Scientists propose the mechanisms of damage to neurons and synapses appear to be caused by

build up of plaques containing the protein beta amyloid

a protein called tau which forms tangles inside neurons and stops them form working properly

inflammation and oxidative stress

How does physical exercise affect the health of our neurons and synapses?

Admittedly, a lot of the scientific research that studies this question at a cellular level has been performed on mice, not humans. Scientists have given some mice the opportunity to run on running wheels, and compared them with sedentary mice who are not allowed to exercise.

How physical exercise effects regular mice:

  • increased neurogenesis
  • reduced age-related decline in neurogenesis
  • increased synapses and connections
  • growth of new capillaries (small blood vessels)
  • increased chemicals needed for neurogenesis and the health and survival of neurons
  • increased chemicals that protect against oxidative stress and inflammation

How physical exercise affects mice with the Alzheimers gene:

  • Compared with sedentary mice with the same genetic mutation, mice given the opportunity for regular physical activity have:
  • reduced beta amyloid plaques
  • increased chemicals needed for clearing amyloid from the brain
  • reduced loss of neurons in the hippocampus (the memory centre of the brain)

What do we know for sure about the effect of physical activity on human brains?

The kind of invasive laboratory experiments performed on the brains of the living mice would never get ethical clearance to be performed on humans. For this reason, we cannot count the number of synapses and neurons in a living brain, but we can use medical imaging techniques to measure brain mass and blood flow.

Studies have shown that people engaging in regular physical activity, compared to those who are sedentary, on average have:

  • increased brain blood flow
  • increased brain grey matter volume, suggesting more neurons and synapses
  • increased volume in the frontal lobes, important for executive functions such as planning and concentration
  • increased volume in the hippocampus, important for learning and memory and significantly affected by Alzheimer’s disease
  • increased brain connectivity, suggesting improved plasticity
  • brain volume and connectivity typical of people a few years younger
  • increased brain-derived neurotrophic factor (BDNF), a chemical important for neurogenesis and the health and survival of neurons
  • reduced age-related brain shrinkage
  • less amyloid deposition in the brain
  • less of the amyloid and tau changes associated with the development of Alzheimer’s disease in the cerebrospinal fluid (the fluid that surrounds the brain and spinal cord)

Researchers at Duke University in the USA reviewed 29 different studies in this area of research and combined their results. Together those studies involved over 2,000 participants. They examined the reported effects of exercise interventions on four kinds of cognitive skills

  • attention and processing speed
  • executive function (planning, initiation, sequencing and monitoring of complex, goal-directed behaviour)
  • memory (retention, recollection and recognition of previously encountered information)
  • working memory (short-term storage and manipulation of information)

They found that overall, physical activity was associated with modest improvements in executive function, memory, attention and processing speed, but not in working memory.
Combined interventions that included aerobic exercise and strength training improved working memory and attention and processing speed to a greater extent than aerobic only interventions.

Participants’ age affected the outcome only for working memory, which improved more for older than younger participants.
People with existing mild cognitive impairment showed smaller improvements in executive function and larger improvements in memory compared to those with normal cognition.
The duration and intensity of physical activity interventions did not influence the outcome for any cognitive function.

It is never too early or too late

Dik and colleagues (2003) found that regular physical activity in early life (15 – 25 years old) was associated with faster cognitive processing speed in men in late life.
Cadar & colleagues (2012) showed that physical activity at ages 36 and 43 years was associated with a slower decline in memory and visual search speed over 20 years in 1018 people in a British study.

The Australian Fitness for the Ageing Brain Study (2010) included 170 people aged 50 or older who reported memory problems or had mild cognitive impairment. They demonstrated improvement in cognitive function in the participants who underwent a 6-month home-based physical activity program, compared to an observed decline in cognitive function in the control group. The findings held true when the researchers re-tested with the participants 12 months down the track.

The majority of studies have employed aerobic cardiovascular activity as a component of their intervention for people with MCI or dementia, often in combination with strength, balance and/or flexibility training.

Heyn and colleagues (2004) pooled data from 30 different randomized controlled trials which studied the effects of exercise on a total of 2020 people aged over 65 who had a diagnosis of dementia or a related cognitive impairment. This meta-analysis demonstrated that exercise training increases fitness, physical function, cognitive function, and positive behaviour in this population of clients.

Studies of people with moderate to severe dementia living in residential care facilities also demonstrate that physical activity provides significant benefits even in the later stages of dementia.

So there you have it.

The exact intensity, duration and frequency that is most effective in mitigating the onset or progression of dementia are not yet known, but is pretty well established that exercise is the most effective method we have available to us to keep our brains healthy. At Next Step Health we like to kill two birds with one stone, so we add mental exercise and cognitive multi-tasking to the cardiovascular component in some of our group exercise classes. When you add cognitive challenges to cardiovascular exercise, it might not be your favourite activity to do, but it is certainly not boring.


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