Professor Nicola Lautenschlager
A definition of physical activity would be any use of your skeletal muscles which needs energy. Research into the link between physical activity and cognition, in later life, is actually quite a new field. So we really only have increasing evidence in the last 20 to 30 years. However, the evidence we have so far is very promising. There are observational and longitudinal studies which have shown for quite a while that people who adhere to physical activity throughout their lifetime have a lower risk of developing cognitive decline when they get older. And more recently, there has also been an increasing number of randomised control trials with either healthy individuals or people in the community who are at higher risk. Especially for the randomised control trials, the evidence is not consistent. So some of the trials were negative but many were also positive. There is a clear indication we need more research done in this field to understand it better.
The positive studies have shown that regular physical activities are associated with improved cognitive performance. Interestingly, there seems to be evidence pointing towards not every type of cognitive performance benefiting in the same way. Currently, most positive studies show that the evidence is especially for executive function or frontal lobe functions, and anything having to do with speed, so for example, processing speed. Whereas for other cognitive areas such as memory, the findings are much more diverse and controversial.
The other interesting finding so far is that it is important to decide what type of physical activity or exercise is most beneficial when you want to maintain your cognitive health, and again the current evidence of the literature points towards aerobic exercise. Meaning it has to be a type of physical activity where there is enough expenditure of energy to have an increased heartbeat, have more intense breathing, basically an activity where the person can’t keep talking, for example, because they need their breath to do the exercise. To give you a practical idea, if you talk about walking which is the most commonly performed type of aerobic exercise, it has to be of a speed and intensity that is reached, that the person develops more laboured breathing and works up a sweat.
It also has been shown more recently that strength training, so specific training where you use, for example, weights to strengthen your muscles, is also beneficial for cognition, and it looks like a combination of both, physical activity with aerobic focus plus strength training, is probably the best combination, rather than doing only one of these types. Where the evidence is more limited is for exercise which is rather focusing on balance or relaxation, like yoga. We know there are lots of benefits for older people, like the reduction of risk for falls and having a better balance, but whether these more low-impact exercises also can help to contribute to cognitive health is not quite clear.
What is still unknown, and needs much more research in the future, is the question, “What is the right dose?” So how much physical activity do you have to do per week, at what level of intensity, to have the best benefits for your cognitive health? There seems to be emerging evidence that a combination of different types, as I mentioned, might be better than just doing one type, and there is also an emerging field which investigates whether combining physical activity with some cognitive tasks might have additional benefit. For example, it has been shown if you have a physical activity type, like dancing, where you also have to remember steps, or Tai Chi where you have to remember movements, this might give you additional benefit. Another area they’re investigating is what we call dual task exercise. That means someone is, for example, in the gym and does aerobic exercise and then in intervals between the physical activity, they try to do a cognitive task like solving a crossword puzzle or doing some arithmetic. So that’s also an interesting area of research.
Australia, like many other western countries, has official physical activity guidelines and we are also fortunate in our country that we have specific guidelines for older Australians. The recommendations for older people are actually very similar to the recommendations for younger people. So there is quite global agreement that the recommended physical activity level we all should try to adhere to is approximately 150 minutes per week. Now how these 150 minutes are spent across the week is very variable. The recommendation is that it shouldn’t be shorter than 10 minutes at a given time. Very often you read a recommendation that trying to do 30 minutes, most days of the week, is a good way to go about it. The recommendations further say the type of physical activity should be mainly moderate aerobic exercise. So that could be either fast walking, or it could be going into a gym program, or it could be bike riding, for example. So there are lots of options. It could be swimming. And then ideally that should be combined with, at least twice a week, some strength training, and obviously outside the benefit for cognition, some balance training to reduce the risk of falls in older people.
So the question, “[Does] it makes a difference if you have done lots of physical activity as a child or a younger person, in terms of the benefits to your cognitive health when you are older?” is a very interesting question. There are studies which have exactly shown that there is, sort of, a lifelong accumulation of your physical activity efforts throughout your lifespan, and the more you have done throughout your life, the better the chances that you have good cognitive health when you’re older. However, there is also research showing that it’s never too late to get started. Looking, for example, at older participants or people who never have done physical activity in their life, who have had a more or less sedentary life and then only started doing physical activity at an older age, even that group can experience some quite impressive benefit with regards to their cognitive health.
The largest amount of evidence in this field we do have for cognitively healthy people, when it comes, for example, to randomise control trials, there is a small but increasing number of studies which focused on people who already experience some cognitive impairment. A classic example would be studies with either older people who have subjective memory decline or, what we call, mild cognitive impairment. Both of these clinical groups have been identified as being at increased risk of later on developing some more pronounced cognitive decline, such as dementia. The study results are less clear in those clinical groups, compared to healthy participants, but there have been a number of trials now which have shown that, also in these clinical groups, there is benefit to cognitive performance, and a few of these studies even have shown that the right type of physical activity program might help to delay the progression of the cognitive impairment.
Professor Nicola Lautenschlager
As one can understand, since the research field is so young, there are lots of hypotheses and theories, but this is probably the area where we still have the biggest limit in terms of knowledge. However, there are quite a few interesting studies, sometimes using animal models, which investigate the question, “What mechanisms, physiologically, for example, do occur, so that the brain benefits directly from physical activity?” More recently, quite excitingly, there are now also study with human participants, investigating the biological background, so to speak, of this correlation. The easiest way, I think, to look at that is to look at two different groups of impact. One would be direct impact on the brain, and the other one would be indirect impact.
So let me start with the latter one. Indirect impact would be anything which benefits, for example, your cardiovascular health, like your blood pressure, your heart, your endocrinological system, your metabolism and therefore the brain benefits, secondary to that. Compared to direct impact, which would be increasing specifically the blood flow to the brain, and therefore assisting the brain with its performance in thinking, or even more excitingly, changing biomarkers, enzymes, hormones, directly in the brain. For example, research has shown that the brain-derived neurotrophic factor or BDNF which we know is very important to help us to learn new things and remember things, can be triggered and activated with physical activity, and this has now also been shown in human trials. Then, obviously not to forget about psychological impact of physical activity. So we do know that most people who find the right type of physical activity do enjoy this greatly, especially older people. It gives them more confidence. Very often it’s a social activity where they meet other people, and therefore usually it has a very good impact on their mental health, and therefore that benefits the brain as well, for example, via reducing stress levels.
If we look at that a bit closer, what biological changes physical activity can achieve in the brain, there are more recently some quite exciting findings in relation to, for example, pathological changes in the brain in association with Alzheimer’s disease or vascular dementia. For example, a study in healthy participants who had to do an aerobic exercise program for a year, could show with modern MRI technology that the volumes of certain areas of the brain, like the hippocampus, were actually growing after the 12 month exercise. Now that was a very unexpected finding, because usually our understanding is that the brain is not growing once you are older, and the study wasn’t designed so that the authors could answer the question why that would happen. But the growth in volume in the hippocampal area in the participants in the intervention correlated with higher levels of their BDNF. So the hypothesis the authors had was actually that the physical activity helped increase connections between the neurons, like creating additional synapses, which help with communication and therefore improve the memory, and that would have lead to the increase of volume.
Now that finding was in comparison to the control group, who not only did not have a growth of the volume but they had a loss of volume, in the same duration, which is what you really would expect in an older person.
Other research has more closely looked at Alzheimer’s disease pathology and there are some early suggestions that physical activity might also be able to directly impact on the amount of amyloid, which is one of the typical deposits associated with Alzheimer’s disease, being present in the brain. So there has been research showing that regular physical activity programs can actually reduce the concentration of that pathological protein you measure in the brain. Why that is the case is not really clear. There are some theories that that might have to do with insulin, because insulin is connected with the deposition of amyloid and we do know, for example, that people with Type 2 Diabetes have a higher risk of Alzheimer's disease.
Professor Nicola Lautenschlager
It’s obviously one thing to conduct the initial research into finding more evidence to establish a clear link between physical activity and the benefits for cognitive health, but, in a sense, the bigger challenge for all of us as societies is how to best translate that knowledge back into our community, so that everybody living in a community, of no matter what age, can have access to programs or information which helps them to do the right physical activity, at the right time, and the right duration, so that they have the best possible outcome for their cognitive health when they are older. The challenge is that a society, as a whole, has to make a decision to invest funds into this area. We are basically talking about here dementia risk reduction activities, and to think about how programs could be made available to community members, which offer the right type of physical activity to help with cognitive health in the future. I think this is a particularly exciting time now, because we have finally accumulated enough evidence that really a first step is to give the knowledge, in obviously appropriate lay terms, to the community, so that the first step would be to increase their knowledge of dementia risk reduction. What we see in many countries now, especially the western countries including Australia, is increasing information via certain bodies, for example Alzheimer's Associations, making the case and providing the information why physical activity is linked to cognitive health. What we do not have yet, internationally, is specific physical activity guidelines with the aim of looking at cognitive health, going beyond the general physical activity guidelines. But there are promising movements now in some countries like the US, the United Kingdom and Canada, who actually are now trying to get all the main international researchers in this field together, to develop specific information, which then can be accessed by the communities in various countries.
Obviously, when we think about physical activities, it’s not just thinking about what programs we could provide, let’s say in certain suburbs or Councils, but it is also about liveability in our cities and suburbs. Because lots of physical activity can be done by just increasing the activity level while you do your everyday jobs, like walking to the shops instead of taking the car, using stairs instead of taking the lift. One interesting area of research is looking at the walkability of suburbs, literally. So how good is the setup, especially for older people, to be able to be more physically active? Is it safe? Are the shops near enough? Are the pathways wide enough? And that obviously translates into other areas such as riding a bike, bicycle tracks and so forth. So this really moves then into planning policy of architecture and design, while cities like the main cities in Australia grow.
I think one point I want to mention which shows you how relatively straightforward the challenge is, is that many of the benefits of physical activity for cognitive health are exactly the same benefits as there are for heart health and for stroke prevention. We know that the recommendations, how to protect your heart from heart attacks, have been around much longer than advice on how to maintain your cognitive health. For example, one easy approach is to give all the necessary information to health clinicians, healthcare providers like general practitioners, to give them a second argument or another argument when they talk to their patients about how to protect their heart health, to say, “And it also helps you to reduce your risk of dementia”. We do know, from surveys of older Australians, that the fear of developing dementia is right in the top range of their health concerns they have for their age group. So it should be a very powerful argument. So looking at programs which could investigate how a general practice could prescribe targeted physical activity, as part of regular health check-ups for older people, would be a very strong way to go.
Professor Kaarin Anstey
We conducted what we call a “meta-analysis” of the smoking literature. We collated all of the published studies that observed smoking, and then followed people to see whether or not they developed cognitive decline, Alzheimer's disease, vascular dementia or all-cause dementia. And we found that smoking in older adults increased their risk of dementia by 70%. And it was pretty much the same for all types of dementia.
Now, unfortunately, we didn’t have the data from middle age to be able to see if that was true of midlife smokers and what happens if people give up. There is one very interesting study that was conducted in Western Australia, on a group of people who entered a smoking cessation program. They took brain scans of these people at the beginning of the program and at the end, and they also tested their cognition. What they found was that the people who gave up smoking had less brain atrophy than the people who continued to smoke. And they also found that people who gave up smoking had less cognitive decline. So that study is really important in showing there are actually benefits for the brain, even giving up smoking in older age.
Smoking impacts on the brain through multiple pathways. We know that smoking increases the rate of ageing on all of the biomarkers that we can measure. Smoking increases the risk of vascular events, so small strokes and stroke. It increases the rate of brain atrophy. It’s a neurotoxin, and of course it increases the risk of a lot of other diseases such as cancer, which can also ultimately impact on the brain. So it’s a pretty general negative risk factor, a negative behaviour to undertake for brain ageing.
Dr Shannon Klekociuk
Ginkgo biloba is an extract taken from the Ginkgo tree, that’s been used in ancient medicines for centuries.
Some evidence suggests that Ginkgo may have anti-inflammatory properties, and that it may help increase blood flow to the brain.
Ginkgo can be taken as an oral supplement or in a tea, and many researchers have looked at whether Ginkgo might be beneficial for a range of different diseases, including those that cause dementia.
Some studies have reported potential benefits of Ginkgo to those with Alzheimer’s Disease or Vascular Dementia, in terms of improving their cognition. However, this finding is not consistent across all studies.
In a recent meta-analysis, researchers were unable to identify any clinically meaningful changes in cognition, activities of daily living, quality of life and psychiatric symptoms, that were related to Ginkgo consumption in people with various diseases that cause dementia.
Other studies of healthy, older adults have failed to find any benefit of Ginkgo supplements for reducing incidence of dementia.
To date, there is no evidence to suggest that Ginkgo can prevent or cure dementia.
Dr Shannon Klekociuk
There’s been significant coverage of coconut oil as a potential treatment for diseases such as Alzheimer’s. As a consequence, some people are now consuming coconut oil in a bid to reduce their dementia risk. Some researchers have suggested that, because the composition of coconut oil is different than other saturated fats, this might provide the brain with fuel for brain cells and potentially reduce the impact of neurodegeneration. Other researchers have suggested that coconut oil might help with the ratio of good to bad cholesterol and that this might be an avenue by which it works to reduce dementia risk. Unfortunately, these are all theories based on limited animal studies. Unfortunately, we have yet to see any evidence from controlled trials that suggests that coconut oil is a preventative measure for dementia or a treatment for diseases such as Alzheimer’s. But research is under way.
An important note here is that coconut oil is 90% saturated fat. Introducing this into your diet can have major ramifications for your health, including weight gain, increases in your blood pressure and changes in your cholesterol. Any dietary modifications must be considered in the context of your individual health status and should always be discussed with a medical practitioner.