Prolonged Stress Causes Memory Loss among Older Adults

Rebecca Lewis June 23, 2014

A new study suggests prolonged stress causes a surge in the hormone cortisol, which can result in short-term memory loss among older adults.

Short-term increases in cortisol are critical for survival as it helps prepare our mind and body against potential threat by activating our flight or fight system. But prolonged high levels of cortisol, which happens when we are stressed, can result to negative consequences – such as high blood pressure, weight gain, digestive problem, and so on.

In the new study involving older adults, researchers from the University of Iowa found a link between high levels of cortisol and the gradual loss of synapses in the prefrontal cortex – the part of the brain that processes short-term memory. Synapses are connections that process, store, and recall information. But repeated and long-term exposure to cortisol can cause them to shrink and disappear.

“Stress hormones are one mechanism that we believe leads to ‘weathering’ of the brain,” said Dr Jason Radley, assistant professor in psychology at the UI and corresponding author on the paper. Like a rock on the shoreline, after years of wave contact, it will eventually break down and disappear.

“And although preliminary, the findings raise the possibility that short-memory decline in aging adults may be slowed or prevented by treatments that decrease levels of cortisol in susceptible individuals,” said Radley.

That could mean treating people who have naturally high levels of cortisol, such as those who are depressed, or those who experience repeated, long-term stress due to traumatic life events like the death of a loved one.

For the study, UI scientists compared elderly rats to 4-month-old rats, which are roughly the same age as a 20-year-old person. The young and elderly groups were then separated further according to whether the rats had naturally high or naturally low levels of corticosterone, the hormone comparable to cortisol in humans.

The researchers subsequently placed the rats in a T-shaped maze that required them to use their short-term memory. In order to receive a treat, they needed to recall which direction they had turned at the top of the T just 30, 60 or 120 seconds ago and then turn the opposite way each time they ran the maze.

Whilst memory decline among all rats was observed as they waited before running the maze again, older rats with high corticosterone levels consistently performed the worst. They chose the correct direction only 58 per cent of the time, compared to their older peers with low corticosterone levels who chose it 80 per cent of the time.

When researchers took tissue samples from the rats’ prefrontal cortexes and examined them under a microscope, they found the poor performers had smaller and 20 per cent fewer synapses than all other groups, indicating memory loss.

In contrast, older rats with low corticosterone levels showed little memory loss and ran the maze nearly as well as the younger rats, who were not affected by any level of corticosterone, low or high.

Still, researchers say it’s important to remember that stress hormones are only one of a host of factors when it comes to mental decline and memory loss as we age.

Source of this article:

Stress hormone linked to short-term memory loss as we age