Staying fit into middle age can reduce the risk of developing Alzheimer’s disease by up to a third, suggests a recent US study led by Dr. Edward Zamrini.

According to The Daily Mail, the study, which analyzed 649,605 people with an average age of 61, found the most fit were 33 percent less likely to develop the disease than the least fit.

Study author Dr. Edward Zamrini, from Washington VA Medical Center, US, said it was "exciting" and "very promising" to see case rates decrease with increased fitness levels, as there are currently "no adequate treatments" for Alzheimer’s.

“So, people can work toward making incremental changes and improvements in their physical fitness, and hopefully that will be associated with a related decrease in their risk of Alzheimer’s years later,” he added.

Researchers examined participants’ "cardiorespiratory fitness", a measure of how well the body transports oxygen to the muscles, and how well they are able to absorb oxygen during exercise.

A limitation of the study was participants were mostly white men so results may not be generalizable to other populations. The findings will be presented at the American Academy of Neurology’s, the world’s largest association of neurologists and neuroscience professionals, 74th Annual Meeting in Seattle.

Physical activity does not only boost blood circulation, but also contributes to increasing chemicals secretions that protect the brain. It could help resist the natural degeneration of communication functions linked to aging as well.

But further research is needed to determine whether physical activity can improve the memory or slow the deterioration of cognitive abilities. Nevertheless, people should exercise regularly to maintain their physical and mental health. The same applies to older people who should remain active, albeit carefully, because activity can bring them many important health benefits.