A daily brisk walk or bike ride could help to reduce older people's risk of Alzheimer's disease, new research has suggested.
We all know that staying active can be vital in terms of giving our physical health a boost, but scientists have revealed regular exercise can also help protect against mental decline too.
That's because physical activity helps to dampens inflammation in the brain, and higher levels of inflammation have been shown to negatively affect cognitive processes.
"No one will disagree that an active lifestyle is good for you," explains lead study author Dr Kaitlin Casaletto, of the University of California, San Francisco.
"But it remains unclear how physical activity improves brain health, particularly in Alzheimer's disease.
"The benefits may come about through decreased immune cell activation."
Dementia affects around 920,000 people in the UK, a figure which looks set to rise to two million by 2050.
The number of people with the condition is steadily increasing because of increased longevity.
It is estimated in the next three decades cases worldwide will triple to more than 150 million.
The complex and debilitating condition is associated with a gradual decline in brain function, and ultimately comes with a terminal diagnosis.
But the condition isn’t always fully understood, which means that people often find it difficult to spot the risk factors associated with it and with no cure in sight, lifestyle changes that can help ward it off, such as daily exercise, are vital.
Watch: New study suggests morning coffee or tea may lower risk of dementia and stroke
Previous studies have revealed a plethora of age-related changes in the brain, and the main immune effectors, known as microglia, are at the centre of these events
Dr Casaletto explains: "Microglia, the brain’s resident immune cells, activate to clear debris and foreign invaders from the brain.
"But too much activation can trigger inflammation, damage neurons, and disrupt brain signalling.
"Exercise helps reduce abnormal activation in animals - but that link hadn’t been established in humans."
For this particular study, published in The Journal of Neuroscience, Dr Casaletto and colleagues tracked 167 older adults to examine the relationship between physical activity and microglia activation.
Study participants were from the Rush Memory and Ageing project, which enrols volunteers without dementia who agree to organ donation.
The participants spanned the spectrum of cognitive ageing and wore activity monitors 24 hours a day for up to ten days straight before annual cognitive exams.
The researchers measured microglia activation and Alzheimer's disease pathology in postmortem brain tissue analyses.
"Greater physical activity was linked to lower microglial activation," Dr Casaletto explains.
She says this was particularly notable in the inferior temporal gyrus, which is a part of the brain which is hit hardest by Alzheimer's.
"Physical activity had a more pronounced effect on inflammation in people with more severe Alzheimer's pathology," Dr Casaletto continues.
"Physical activity relates to better cognitive ageing and reduced risk of neurodegenerative disease," she adds.
For healthy adults doctors recommend at least 150 or 75 minutes of moderate or vigorous aerobic activity, respectively, each week.
Read more: What are the risk factors for dementia?
According to Alzheimer’s Society risk factors increase a person’s risk of developing dementia over a period of time.
But there are also protective factors, such as physical exercise, that can help to lower a person’s risk of the developing the condition.
Though some risk factors for dementia cannot be avoided or controlled – such as age, genetics, gender and ethnicity, other factors are ‘modifiable’, meaning we can take action to change them and potentially reduce the risk of dementia.
The six risk factors are heavy drinking, genetics, smoking, high blood pressure, depression and diabetes, while physical exercise is a protective factor against the disease.
The Alzheimer's Society say middle aged and older adults who engage in regular aerobic exercise have lower rates of Alzheimer’s disease and vascular dementia.
Studies estimate the protective effect to be about 30-40% reduced risk of dementia compared to those who do little or no physical activity.
As well as physical activity, there are some other modifiable risk factors of Alzheimer's.
Modifiable risk factors
Smokers are at an increased risk of both Alzheimer’s disease and vascular dementia with research estimating the effect is between a 30% and a 50% increase in risk depending on the study and type of dementia.
Traumatic head injury
A severe injury to the head could increase the risk of dementia later in life. “There is lots of variability between studies on the size of the effect but a study of 200,000 US war veterans suggests a severe head injury can increase the risk of dementia by up to 60%,” Davies reveals.
The benefits of following a Mediterranean-style diet have long been discussed, but a diet with a high proportion of oily fish, fruit, vegetables, unrefined cereals and olive oil, and low levels of red meat and sugar is also associated with a reduced risk of dementia. Studies estimate that it could reduce the risk by about around a third.
Type 2 diabetes
According to Alzheimer’s Society people with type 2 diabetes are about 60% more likely to develop dementia than non-diabetics.
High blood pressure
Long-term research studies have demonstrated that high blood pressure in mid-life is a key factor that can increase your risk of developing dementia in later life. These findings highlight that a lifelong approach to good health is the best way to lower your risk of dementia.
Additional reporting SWNS.
Anyone with concerns about Alzheimer's Disease and dementia should contact the Alzheimer’s Society Dementia Helpline on 0300 222 1122.