BALTIMORE — Feel like you’re at wits’ end lately? Research shows today’s stressors can impact future brain functioning, especially for women. It is this gender difference that was the subject of a recent study conducted by researchers at Johns Hopkins University.
The longitudinal study confirms Alzheimer’s Association statistics: One in six women over the age of 60 — compared to just one in 11 men — will eventually be diagnosed with dementia. Could one trigger be midlife stress that unfairly targets women?
“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 Cynthia Munro, Ph.D., associate professor of psychiatry and behavioral sciences at the university’s School of Medicine, in a Hopkins release. “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.
The current study expands on previous research about stress and aging. From other studies, we know that in terms of age-related stress response changes, women experience triple what men experience. Other research confirmed that extremely stressful times in life can cause temporary memory and cognitive problems. So how do these two pieces of information relate to memory loss in later life?
Researchers wanted to understand how stressful life experiences might impact long-term memory problems, particularly in women. They studied data on 909 Baltimore-area adults who took part in the National Institute of Mental Health Epidemiologic Catchment Area study from 1981 through 2004. More than half of participants (63%) were women and 60% were Caucasian.
Participants were enrolled in 1981 and asked to return to trial sites for interviews and checkups three more times spanning more than two decades. The first followup was in 1982. The second followup was between 1993 and 1996. At this time (the mid-life checkup), the participants were an average age of 47. The third followup occurred in 2003 or 2004.
At their mid-life checkup, the participants were asked about traumatic events in the past year (e.g., combat, rape, mugging, physical attack, threat, natural disaster, exposure to violence). About a quarter (22% of men and 23% of women) had experienced at least one traumatic event within the past year.
At this visit, they were also asked about other stressful life experiences (e.g, marriage, divorce, death of a loved one, birth of a child, job loss, severe injury or sickness, child moving out, retirement). About half (47% of men and 50% of women) had experienced at least one of these events in the last year.
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Researchers used a standardized learning and memory test to measure abilities at the mid-life checkup in the 1990s and again at the final checkup in the 2000s. The tests involved recalling 20 words immediately after hearing them and then coming up with the words again 20 minutes later.
During their mid-life visit, participants were able to recall an average of eight words right away and six words 20 minutes later. At their final followup, this dropped to seven and six words, respectively.
Participants also were asked to select the words spoken to them from a written list of 40 words. At mid-life, participants were able to pick out an average of 15 words correctly. At their final checkup, recognition had dropped to fewer than 14 words.
The researchers then looked for any connection between reported traumatic or stressful life events in middle age and changes in testing performance between the two checkups during which memory tests were conducted.
The study results found that the more stressful life experiences a woman had in midlife, the more likely she was to experience a decline in recalling and recognizing words in later years. Word recognition declined by an average of 1.2 words for women without stressors at midlife but fell by 1.7 words for women who had experienced at least one stressor in midlife.
Women who reported one-time traumatic events at midlife, however, did not experience these declines. Researchers say that this finding suggests that it is ongoing stress — the type experienced when there is, say, a long-term illness — that does the most damage to brain functioning.
“Chronic stress can impair the body’s ability to respond to stress in a healthy manner,” Munro says.
“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,” adds Munro. “We know if stress hormone levels increase and remain high, this isn’t good for the brain’s hippocampus — the seat of memory.”
For the men studied, researchers say no link was found between either type of stress in midlife and a loss in word recall or recognition later. Study authors also report that stress in early life is not a good predictor of later cognitive decline in either women or men.
Although it appears that ongoing stress at midlife is most harmful to women, researchers caution that the results of this study do not prove cause and effect. But if future studies establish that stress response is the cause of dementia, then stress management and other interventions–such as medications currently in development–could help relieve the body’s chemical response to stress and help avoid or delay cognitive decline.
Findings are published in the July 2019 issue of the International Journal of Geriatric Psychiatry.