Stress and Memory Loss: The Older We Get, the Less We Remember

As people age, they might not remember quite as much. Yet this relatively common process can be accentuated by stress.

A new study, published in the Journal of Neuroscience, shows how high cortisol levels--a natural hormone released by the body during times of high stress--can create memory problems.

Though short-term increases of cortisol levels can be critical for survival, long-term stress in which cortisol spikes for abnormally long periods or high levels can lead to negative consequences that increase risk of anxiety, high blood pressure, digestion problems and weight gain.

During the experiment, researchers from the University of Iowa (UI) found a connection between elevated cortisol levels and gradual loss of synapses in the prefrontal cortex--a region of the brain that stores short-term memory. These synapses form connections that help individuals process, recall and store information properly. Unfortunately, as we age, long-term exposure to cortisol levels can cause these areas to shrink and even disappear.

"Stress hormones are one mechanism that we believe leads to weathering of the brain," said Jason Radley, assistant professor in psychology at the UI and corresponding author of the paper, in a news release.

For the study, researchers compared elderly rats (rodents 21 months or older) to 4-month-old rats. The elderly rats would be around 65 if they were human. The younger 4-month-olds would be about 21. Both groups were separated based on their ages to determine corticosterone levels.

Researchers placed the rats in a T-shaped maze to first become familiar with the area and then to find a treat. Yet in order to find the treat, the rats would need to call on their short-term memory to remember the pathways they had taken just 30, 60 or 120 seconds ago.  

Though memory declined across all groups during the time the rats waited before going in the maze again, older rats showed higher corticosterone levels that consistently made them perform worse than younger rats. In fact, findings showed that they only chose the correct path about 58 percent of the time while the young rats chose it about 80 percent of the time.

Examination of the older rat's prefrontal cortex also showed that poorer performers had about 20 percent fewer synapses than others, which indicated signs of memory loss.