New US research has found that experiencing stressful life events during middle age can negatively affect a woman's memory and possibly increase her risk of dementia later in life.
Carried out by researchers at Johns Hopkins Medicine, the new study looked at 337 men and 572 women with an average age of 47 years who were asked to undergo several check-ups and interviews between 1982 and 2004.
In the final checkup, participants were asked if they had experienced a traumatic event in the past year such as combat, rape, a mugging, any other type of physical attack, watching someone else attacked or killed, receiving a threat, or living through a natural disaster, and if they had experienced any stressful life experiences such as marriage, divorce, death of a loved one, job loss, severe injury or sickness, a child moving out, retirement, or birth of a child.
The participants were also asked to complete a learning and memory test at the third and fourth visits, and the researchers measured any decreases in performance on the tests.
The findings, published in the International Journal of Geriatric Psychiatry, showed that for women, having a greater number of stressful life experiences over the last year in midlife was linked to a greater decline in the memory test. The more stressful life experiences the women had, the more difficulty they had with the test.
However, the researchers did not see the same association in women who experienced traumatic events, possibly because long-term stress, or "chronic stress, such as the stress experienced during a divorce, may have more of a negative impact on brain functioning than distinct traumatic events.
"A normal stress response causes a temporary increase in stress hormones like cortisol, and when it's over, levels return to baseline and you recover. But with repeated stress, or with enhanced sensitivity to stress, your body mounts an increased and sustained hormone response that takes longer to recover," says study author Cynthia Munro, PhD.
"We know if stress hormone levels increase and remain high, this isn't good for the brain's hippocampus -- the seat of memory."
The researchers failed to find an association in men between their performance on the tests and experiencing either stressful life experiences or traumatic events in midlife.
According to the team, the findings do not determine cause and effect, but do add to an existing body of evidence that stress hormones play an uneven gender role in brain health. Rates of Alzheimer's disease are also higher among women than men.
"We can't get rid of stressors, but we might adjust the way we respond to stress, and have a real effect on brain function as we age," says Munro. "And although our study did not show the same association for men, it sheds further light on the effects of stress response on the brain with potential application to both men and women," she adds.