Regular exercise for over-50s could be vital in reducing the risk of developing Alzheimer's disease, according to scientists.

Researchers at the University of Kentucky College of Health Sciences have demonstrated a positive correlation between fitness and blood flow to areas of the brain where the hallmark tangles and plaques of Alzheimer's pathology are usually first detected.

Published in the latest issue of NeuroImage, the study saw 30 men and women aged 59-69 put through treadmill fitness assessments and ultrasounds of the heart. They then received brain scans to monitor blood flow to certain areas of the brain.

"We set out to characterise the relationship between heart function, fitness, and cerebral blood flow, which no other study had explored to date," said lead author Dr Nathan Johnson.

"In other words, if you're in good physical shape, does that improve blood flow to critical areas of the brain? And does that improved blood flow provide some form of protection from dementia?"

The results showed higher blood flow to critical areas of the brain, meaning the supply of oxygen and vital nutrients was higher in those who were more physically fit. Researchers concluded that regular exercise at any age could keep the mind young.

"Can we prove irrefutably that increased fitness will prevent Alzheimer's disease? Not at this point," added Johnson.

"But this is an important first step towards demonstrating that being physically active improves blood flow to the brain and confers some protection from dementia, and conversely that people who live sedentary lifestyles, especially those who are genetically predisposed to Alzheimer's, might be more susceptible."

There is a growing body of research looking at the relationship between exercise and Alzheimer's. In one instance, US researchers are studying a group of 300 people, all aged over 100-years-old, living in a remote Italian village nestled between the ocean and mountains on the country's coast. The group is known to have very low rates of heart disease and Alzheimer's, with scientists hoping to identify the precise dietary and exercise elements which are key to their longevity.