People who are at risk of being diagnosed dementia can potentially reduce their odds of developing the condition by more than a third if they are fit and healthy, a new study suggests.

Having high “cardiorespiratory fitness” (CRF) – which can be achieved through exercise – has been linked to a 35% reduced risk among those deemed to be at risk of dementia, researchers found.

Experts said that “enhancing CRF could be a strategy for the prevention of dementia” after making the discovery.

The researchers suggest that people who were in the “medium” risk group who had a better cardiorespiratory fitness may be able to decrease their risk of developing dementia by 35%.

The new study, published in the British Journal of Sports Medicine, saw academics analyse data on more than 60,000 people taking part in the UK Biobank study.

At the start of the study, people were given a number of tests, including a fitness test to assess their CRF, measured after a stint on an exercise bike.

The researchers note that CRF refers to “the capacity of the circulatory and respiratory systems to supply oxygen to skeletal muscle mitochondria in order to meet the energy demands of physical activity”.

The people taking part in the study were also given a number of tests to assess their thinking and memory, and how quickly they could process information.

Researchers also analysed their “polygenic risk scores” by looking at whether each person had any common genetic variants associated with Alzheimer’s disease and dementia risk.

The group, who were an average age of 56 at the start of the study, were tracked for almost 12 years to see whether they were diagnosed with dementia.

During the follow-up period, some 553 people were diagnosed with dementia.

After comparing the information, the researchers found that people with high CRF appeared to have a 40% reduced risk of dementia compared to people with low CRF.

They also discovered that people with high CRF who did develop dementia tended to develop it later in life compared to those who had low levels of CRF.

And among people with a moderate or high polygenic risk score, high CRF “attenuated all dementia risk by 35%”, they said.

The researchers, led by academics from Tianjin Medical University in China, wrote: “In this large community- based longitudinal study from the UK Biobank, we found that higher CRF was associated with: (1) better baseline global cognitive function and performance in multiple cognitive domains; (2) lower risk of dementia and a delay in the onset of dementia across middle and older age; and (3) 35% reduction in the risk effect of genetic predisposition on all dementia risk.”

They added: “CRF may be used as a predictor of cognitive health” and “enhancing CRF could be a strategy for the prevention of dementia, even among people with a high genetic predisposition for Alzheimer’s disease.”

Commenting on the study, Dr Jacqui Hanley, head of research at Alzheimer’s Research UK, said: “According to the latest research, nearly half of dementia cases globally could be prevented or delayed by addressing 14 risk factors, and keeping active is one of them.

“This new research highlights how good cardiorespiratory fitness, a key measure of overall physical health, could help lower the risk of developing dementia in the future.

“However, it is important to note that we don’t know if there is a direct link between cardiorespiratory fitness and reduced dementia risk, more research is needed to find out exactly how it effects the brain.

“Certain dementia risk factors we can’t change, like age and genetics.

“Interestingly, this study also looked at cardiorespiratory fitness in people who had variations in their genes that increases their risk of developing Alzheimer’s disease. The researchers suggest that people who were in the ‘medium’ risk group who had a better cardiorespiratory fitness may be able to decrease their risk of developing dementia by 35%.

“Understanding this interaction more could reveal new ways to help prevent dementia from developing in people who are at a higher risk.

“But what we do know is that dementia is not an inevitable part of ageing, and there are things we can all do to help reduce our risk of developing the condition in the future.”

Dr Richard Oakley, associate director of research and innovation at Alzheimer’s Society, said: “This research emphasises that exercise is an important part of maintaining a healthy lifestyle and could reduce the risk of developing dementia later in life. It’s positive to see this highlighted once again in a large study of more than 60,000 people indicating the importance of healthy lifestyle changes to lower your risk of dementia.”

He added: “It’s never too early or too late to make healthy changes, no matter what your genetic risk is.

“However, this study did not consider specifically how exercise lowers risk. We would welcome more research to better understand the underlying mechanisms involved and how best to support people to make healthy changes to help end the devastation caused by dementia.”