New research has revealed that walking at least 6 miles (9.7km) each week may help to protect brain size and enhance memory in later life.

A total of 299 dementia-free people participated in the study, the results of which have been published in Neurology - the medical journal of the American Academy of Neurology (AAM). Participants recorded the number of blocks walked in one week, before undergoing brain scans nine years later to measure their brain sizes.

At the nine-year point, it was found that participants who walked at least 72 blocks per week - between 6-9 miles (9.7-14.5km) - had greater grey matter volume than those who didn't. Further tests four years on from the nine-year point revealed that 40 per cent of participants had developed memory problems or dementia; most of whom had not walked at least 72 blocks.

Study author Kirk Erickson of the University of Pittsburgh said: "Our results should encourage well-designed trials of physical exercise in older adults as a promising approach for preventing dementia and Alzheimer's disease. "If regular exercise in midlife could improve brain health and improve thinking and memory in later life, it would be one more reason to make regular exercise in people of all ages a public health imperative."