Combining exercise and computer use could help to reduce the risks of dementia, a study claims.

Researchers in Minnesota found an association between engaging in moderate exercise and mentally stimulating activities in reducing the risks of dementia, according to a study published in Mayo Clinic Proceedings.

The study had more than 920 people between the ages of 70 and 93 in Olmsted County, Minnesota, complete questionnaires detailing the amount of time they exercise and spend on computers over the previous year.

Of those who both exercised and used a computer, 18.3 percent showed signs of mild cognitive impairment (dementia), compared to 37.6 percent who did neither. Of those who did both, 36 percent were declared cognitively normal, while 20.1 percent were normal in the group that did neither.

Experts warn that the world's ageing population will lead to major increases in the number of people who sufferer from dementia and other degenerative mental conditions, such as Alzheimer's.

A spokesman for the Alzheimer's Society said: "There is already considerable evidence to show that donning the walking shoes, or hitting the tennis courts can have real benefits for your head as well as your heart.

"Although we need to know more before we can say for sure whether using computers has real additional benefits and why this could be, we would encourage any older people who enjoy using them to keep it up.

"The best way to reduce your risk of dementia is to exercise regularly, eat a healthy diet, don't smoke and get your blood pressure and cholesterol checked by your GP."