140 people with “pre-dementia”, or mild cognitive impairment, will be studied over an 18 month period as their conditions will develop. Blood and saliva samples will be taken at six month intervals to measure stress markers.

Past work on the subject has suggested that stress at mid-life could indeed be a factor in dementia. A Scottish study led scientists to conclude that there might be something in the hormone the body releases to deal with stress.

Meanwhile another previous study by Swedish scientists found the risk of dementia was about 65% higher in women who reported repeated periods of stress in middle age than in those who did not.

Leading the new study will be Prof Clive Holmes from the University of Southampton, and he said: "All of us go through stressful events. We are looking to understand how these may become a risk factor for the development of Alzheimer's.

"Something such as bereavement or a traumatic experience - possibly even moving home - are also potential factors. This is the first stage in developing ways in which to intervene with psychological or drug-based treatments to fight the disease.”