The memory loss affecting many seniors may be the product of too much stress. A recent study finds evidence that high levels of cortisol — a naturally occurring stress hormone — lead to memory lapses as we age.
Cortisol helps us survive. It helps us respond to challenges by making us more alert. But there can be too much of a good thing. Prolonged periods of high cortisol levels, such as occur during long-term stress, are associated with digestive problems, anxiety, weight gain and high blood pressure.
Elevated cortisol levels also produce a gradual loss of connections among brain cells, according to University of Iowa researchers. These connections help us process, store and recall information, and it appears that long-term exposure to cortisol causes them to shrink or disappear.
Tissue samples showed fewer and smaller connections between brain cells — a hallmark of memory loss — among rats with high cortisol levels.
“Stress hormones are one mechanism that we believe leads to weathering of the brain,” Jason Radley, an author of the study and assistant professor of psychology at the University of Iowa said in a statement.
The results, though preliminary, suggest that declines in short-term memory of aging adults might be helped by drugs that reduce cortisol levels in susceptible individuals, Radley says. Early treatment of people with naturally high cortisol levels — the severely depressed, those who've experienced long-term or repetitive stress due to traumatic life events such as the death of a loved one or illness — may help preserve the connections in the prefrontal cortex.
Short-term memory lapses related to cortisol start to show up around age 65. That's about the equivalent of 21-month-old rats, which was the age range of animals studied in order to make this discovery.
The research group found that older rats with high levels of cortisol consistently performed the worst in a maze test. They chose the correct direction only 58 percent of the time, compared to older rats older with low corticosterone levels, who chose the correct route 80 percent of the time.
Tissue samples showed fewer and smaller connections between brain cells — a hallmark of memory loss — among rats with high cortisol levels. This was in stark contrast to older rats with low corticosterone levels. They showed little memory loss and ran the maze nearly as well as the younger rats.
The study is published in the Journal of Neuroscience.