Scientists claim to have discovered how stress can contribute to memory loss in old age. University of Edinburgh researchers have shown how two receptors in older brains react to the stress hormone cortisol which has been linked to increasing forgetfulness as people age.

The study on older mice found that one receptor was activated by low levels of cortisol, which helped memory.

However, once levels of the hormone were too high they spilled over on to a second receptor, activating brain processes which contribute to memory impairment.

When the receptor linked to poor memory was blocked, the memory recall problem was reversed.

Scientists say the discovery could lead to treatment for conditions such as early Alzheimer’s.

Joyce Yau, who led the study at the university’s Centre for Cardiovascular Science, said: “While we know that stress hormones affect memory, this research explains how the receptors they engage with can switch good memory to poorly functioning memory in old age.

“We now know that lowering the levels of these stress hormones will prevent them from activating a receptor in the brain that is bad for memory. Understanding the mechanisms in the brain which affect memory as we age will help us to find ways to combat conditions linked to memory loss.”

The research helps explain why too much stress over a prolonged period interferes with the normal processes in storing everyday memories, despite the fact that a little bit of stress can help people better remember emotional memories.

Scientists found that high levels of cortisol in aged mice made them less able to remember how to navigate a maze.

Chris Kennard, professor, and chairman of the MRC’s neuroscience and mental health board, said: “This research highlights some interesting, original concepts relating to why memory loss occurs in old age.

“With people living ever longer, the MRC is really focusing on research which allows elderly people not just to survive but also to stay healthy.”

The researchers are looking at a new chemical compound which blocks an enzyme, known as 11beta-HSD1, which helps produce stress hormones within cells.

They hope this could be used to develop a drug treatment to slow the normal decline in memory associated with aging, or even improve memory in people who are very old.