Stress We sometimes joke about how our memory seems to get worse as we get older, but for many of us it’s no laughing matter. Now scientists at the University of Edinburgh have uncovered a hormonal connection between memory loss and stress in older people that could help research into treatments.
"It’s quite well known that too much stress hormone is bad for memory, and previous research has found that as we get older, about 30% of us have impaired memory, some have memories just as good as young people and then there are some that are in between," said Dr Joyce Yau, of the University of Edinburgh’s Centre for Cardiovascular Science, who led the study, which was funded by the Medical Research Council.
Other research carried out in the past has found that older people who had poorer memory, and shrinkage of the hippocampus (one of the key areas of the brain involved in memory) also had increasing levels of the stress hormone cortisol over the years. "I’ve done studies in the past, where if you kept the levels of these stress hormones low, in animal subjects, it prevented memory impairment," explained Dr Yau. "In some older people, their mechanism for bringing cortisol levels back down after stress isn’t so good. So they tend to have higher than normal levels most of the time, and this is part of the reason why their memory is impaired."
The study, published in the Journal of Neuroscience, found that high levels of the stress hormone in older mice made them less able to remember how to navigate a maze. When the stress hormone is released at low levels, it activates a receptor in the brain which actually helps our memory. But if levels of the stress hormone rise too high they can spill over onto a second receptor, which can result in memory problems.
"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," said Dr Yau. "We now know that lowering the levels of these stress hormones will prevent them from activating a receptor 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."
"Since we’re living longer, and there’s currently no treatment for Mild Cognitive Impairment (MCI), this could help to improve our quality of life as we get older. Even a small memory loss can affect you in your ability to do things every day.
"It’s quite exciting that we can actually reverse memory impairments in already very old mice. They were impaired one week, we gave them a drug and the next week they were fine . Whether that’s going to be the case in humans, we don’t know. The aim is to take a drug into clinical trials and eventually have a treatment to improve memory in elderly patients, and even possibly help in early Alzheimer’s disease and other age-related memory-loss problems," said Dr Yau. "It’s early days, but we’re quite optimistic that this will do some good."
Clinical colleagues at the University of Edinburgh are investigating a new chemical compound that blocks an enzyme – 11beta-HSD1 - that is involved in producing stress hormones within cells. Work on this is continuing, but it’s likely to be three to four years before trials have finished and the drug reaches our chemists’ shelves.
First published April 7, 2011