A brisk walk a day switches on a brain process that can protect against Alzheimer’s, according to a new study.

A stress hormone produced during moderate exercise protects the brain from memory changes linked to the disease, found the study by the University of Nottingham.

They may have abnormal functioning of the protective hormone and its related brain receptor.

There is growing evidence that physical and mental activity can cut the chances of developing Alzheimer’s, or slowing its progression, but until now it has been unclear what mechanism is involved.

Dr Marie-Christine Pardon and colleagues carried out work to establish the role of the stress hormone CRF (corticotrophin-releasing factor) in the onset of the disease. Normal levels of CRF are beneficial to the brain, keeping the memory sharp, and studies have found Alzheimer’s sufferers have reduced CRF levels.