High levels of cortisol, also known as the stress hormone increase the risk of short-term memory loss in older adults, a new study finds.

Cortisol is a hormone in the body that is released when a person is under stress. Previous studies have established that increase in cortisol levels in the body once in a while is crucial for survival. It helps a person cope with life's challenges. However, a prolonged increase in the production of this hormone can have negative health consequences. A new study by researchers from the University of Iowa found that high levels of cortisol hormone increase the risk of short-term memory loss in older adults.

The researchers studied a group of 21 month-old and 4-month old rats. Researchers first noted whether the rats naturally had high or low levels of corticosterone (the hormone comparable to cortisol in humans.) After this, the rats were placed 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 in the maze.

The researchers found that older rats with high corticosterone levels performed the worst. They chose the correct direction only 58 percent of the time compared to 80 percent in rats with lower levels of corticosterone.

Explaining the mechanism behind this, researchers said that an elevation in the amount of cortisol results in the slow loss of synapses in the prefrontal cortex, the region of the brain that houses short-term memory. Synapses are the connections that help us process, store and recall information. On studying tissue samples of the rats' prefrontal cortex, researchers found that those with higher levels of corticosterone had 20 percent fewer synapses than those with lower levels of corticosterone.  And when we get older, repeated and long-term exposure to cortisol can cause them to shrink and disappear.

The findings of this study suggests that short term memory loss can be prevented or slowed in older adults by subjecting them to treatments that lower the level of cortisol in their body.  Previous studies have linked higher levels of cortisol to health issues like digestion problems, anxiety, weight gain and high blood pressure.

The new study was published in the Journal of Neuroscience and was funded by National Institutes of Health.