How Exercise Can Help Stop Alzheimer’s Disease
Exercise is a powerful brain protector - here's what you need to know
Exercise, as you know, has many positive benefits. Aside from raising your buff rating, it improves all aspects of health, from pulmonary and musculoskeletal fitness, from immunity to metabolism. It is celebrated for its heart-health benefits, and because cardiovascular fitness is considered a predictor of long-term health, exercise can also extend your life expectancy.
However, there’s another area of exercise research that is proving to be just as positive, and that’s brain health. It’s becoming increasingly clear that the right kind of exercise can help prevent the onset of dementia, including Alzheimer’s disease.
“A rapidly growing literature strongly suggests that exercise, specifically aerobic exercise, may attenuate cognitive impairment and reduce dementia risk.”
You can see the logic: the brain requires nutrients and oxygen, and that’s what exercise delivers.
Alzheimer’s is a form of dementia. It doesn’t appear overnight: before it takes hold, there is a pre-dementia stage called mild cognitive impairment (MCI). At this stage, there may be minor memory problems, difficulty thinking and concentrating, or just doing normal everyday things. Nothing too serious, but a worry all the same.
It is estimated that 15%-20% of people aged 65 and over have MCI. About half of those people will develop dementia within five years of diagnosis.
MCI means reduced brain function. Although usually associated with the ageing process, it is not inevitable: ever more studies suggest that exercise can slow down the progression of memory loss, and may be ‘one strategy to prevent or delay cognitive decline.’
One fairly early study, published in 2006, followed and assessed 1,740 individuals aged 65 plus and based in Washington. None had cognitive impairment, and all scored well in brain screening tests. Around six years later, it was found that those who exercised three or more times a week were significantly less likely to develop Alzheimer’s than people who exercised less than three times per week.
But that was just one study, and despite the positive results, it doesn’t prove anything. Perhaps people who exercise regularly are generally more health-aware than people who don’t. Perhaps they eat better diets, have higher incomes, and are less likely to smoke.
Establishing the facts has become a matter of urgency. It is estimated that by 2030, 20% of people in the US will be aged 65 or more, and according to the Alzheimer’s Association, one in 3 of those people will die with a form of dementia.
That’s why in 2014 the Alzheimer’s Association was asked by the World Dementia Council, an organisation created in 2013 by the G8 nations meeting in London, to research and report on all the available evidence for modifiable risk factors for dementia. Their analysis of systematic reviews, meta-analyses, cross-sectional studies, and randomized controlled trials led the Association to state that:
“…the Association believes there is sufficiently strong evidence, from a population-based perspective, to conclude that regular physical activity and management of cardiovascular risk factors (diabetes, obesity, smoking, and hypertension) reduce the risk of cognitive decline and may reduce the risk of dementia.”
How does it work?
Exercise increases blood flow to the brain: intense bursts of physical exercise increase the heart rate in order to increase oxygen delivery. Therefore, cerebral blood flow increases.
That’s great, obviously, but the really interesting effect appears to be something else.
In Alzheimer’s, there is a loss of neurons (brain cells) and synapses (a synapse is the structure between nerve cells that allows transmission of messages). This occurs in various areas of the brain, and the result is atrophy — shrinkage — in those areas.
Areas that are affected include the hippocampus and prefrontal cortex. Both of these areas, especially the hippocampus, are important for memory. Shrinkage of the hippocampus in late adulthood leads to impaired memory and increased risk of developing dementia.
Exercise has three exceptionally promising effects on those areas of the brain most associated with memory.
First, exercise increases the size of the hippocampus, leading to improvements in memory and reversal of age-related loss in volume.
Second, exercise triggers neurogenesis — the creation of new brain cells. Cerebral tissue is expanded by aerobic exercise, and this increases the amount of grey and white matter in areas of the brain that are important for cognitive function, including the prefrontal cortex.
The third effect is the subject of much scientific scrutiny, because it is potentially a game changer in the search for a cure for dementia. Exercise increases levels of a protein called ‘brain-derived neurotrophic factor’, or BDNF, in the hippocampus and other brain regions.
In the brain-healthy individual, BDNF is abundant in the hippocampus. This protein increases the size of the hippocampus, increases production of new neurons and prevents the death of existing neurons.
The more physically fit the older adult, the greater the hippocampal volume. According to researchers, loss of hippocampal volume in late adulthood is not inevitable — it can be reversed with moderate-intensity exercise, and the result is higher BDNF and improved memory.
Conversely, if the hippocampus shrinks, there is greater risk of impaired cognitive function and dementia.
What type of exercise?
In short, you need to do aerobic exercise. Lifting weights won’t cut it: BDNF appears to respond well to aerobic exercise but not strength training.
Even so, you don’t have to run yourself into the ground to raise those BDNF levels: high intensity activity is effective, but so too is moderate activity.
“In this randomized controlled study of exercise training, we demonstrate that loss of hippocampal volume in late adulthood is not inevitable and can be reversed with moderate-intensity exercise.”
Neither should you worry that you’ve left it too late to change your idle ways.
“These results clearly indicate that aerobic exercise is neuroprotective and that starting an exercise regimen later in life is not futile for either enhancing cognition or augmenting brain volume.”
How long?
Once you start an exercise programme, there can be no going back; there is no completion date. When it comes to both MCI and dementia, the longer the better, it would appear, for improving the size of the hippocampus and spatial memory.
Slump back to a sedentary lifestyle, on the other hand, and levels of BDNF will start to reduce.
How much?
The obvious answer is as much as you can fit in to your routine. As a rough guide, it is fair to assume that a minimum of fifteen minutes a day is reasonable. That level of frequency has indeed been found to be effective.
In one study, one group of 30 people jogged for minimum 15 minutes a day, for 60 days. A second, control group of 30 did no exercise, for the same period. At the end of the test period, BDNF levels were measured, and cognitive function assessed. The exercise group scored significantly better on the Mini-Mental State Examination, a 30-point questionnaire widely used in clinical settings. The exercisers also had significantly higher levels of BDNF than the non-exercise group.
“In conclusion, physical exercise in the form of jogging for at least fifteen minutes every day was able to maintain geriatric cognitive function performance by BDNF protein regulation.”
What about other brain conditions?
It stands to reason that if exercise is good for the brain, it must be good for other mental health conditions, beyond dementia.
In children, clinical studies have shown that exercise increases brain volume and improves cognition in those with reading difficulties. This is important for children because their brains are highly plastic. Plastic in this sense means that the brain is changeable and can form new connections, especially in response to learning. Exercise enhances brain plasticity meaning it allows the brain to change — and therefore heal, with the help of BDNF.
Even in adulthood, the brain remains plastic and changeable. But if levels of BDNF are low, that could be an indication of several psychiatric disorders. Those disorders where BDNF levels have been found to be reduced include major depressive disorder, bipolar disorder and schizophrenia. Interestingly, antidepressant treatment usually increases blood BDNF.
“Patients with psychiatric and neurodegenerative disorders often have reduced BDNF concentrations in their blood and brain.”
What else raises BNDF?
I’m glad you asked. As well as doing regular aerobic exercise, there’s something else you can take up: intermittent fasting. Combine aerobic exercise with regular intermittent fasting, and you can expect even greater enhancement of cognitive function. Intermittent fasting is a pattern of eating based on extended periods of abstinence, and I wrote about how this works here:
Despite the huge amount of research and money that has been funneled towards the search for a cure for dementia, none has been found. In the absence of an effective pharmaceutical intervention, the condition is considered untreatable.
But that doesn’t mean that there is no hope, or nothing that we can do to help ourselves. Exercise and good diet may be all you need.
For those of us "of an age", i.e. over 70, the prospect of Alzheimer's is worrying. If you are in that category, there is an option for tracking your mental state for free. Several years ago I joined a study of the disease. Every 3 months I take a test online that assesses my mental state. The results are available to me, along with some guidelines on interpreting them. In this way I can see a history of my tests, and can detect any indication that I'm drifting into MCI. I'm happy to report that my ancestral diet, daily 5k walk, and one meal a day have kept me in a state of normal.