Stressful life events—like being fired from a job, getting divorced, or fighting in a war—can age the brain by up to four years, according to a study presented yesterday at the Alzheimer’s Association International Conference in London. And the more stressful experiences people in the study had, the poorer their cognitive functioning was later in life.
The study, which has not been published in a peer-reviewed medical journal, also found that African Americans seem to be most at risk for stress-related brain changes. Not only did African-American study participants report more than 60% more stressful events than their white counterparts, but each individual experience was also linked to worse cognitive results.
In white participants, each stressful experience was associated with brain changes equaling about a year and a half of normal brain aging, according to a report from NPR. In African Americans, each event aged the brain an average of four years.
While the study didn’t look for dementia symptoms specifically, the authors point out that the prevalence of Alzheimer’s disease is rising—and that minority communities are affected at disproportionate rates. "Adversity is a clear contributor to racial disparities in cognitive aging, and further study is imperative," said lead author Megan Zuelsdorff, PhD, a research associate at the University of Wisconsin School of Medicine and Public Health, in a press release.
The study involved a total of 82 African-American adults and 1,232 non-Hispanic white adults. All participants answered questions about stressful experiences throughout their lives, including educational difficulties, interpersonal conflicts, financial insecurity, legal or justice-system issues, serious health events, and psychological or physical trauma. They also completed cognitive tests that measured memory and problem-solving abilities.
Both groups—the African American participants and the white participants—were highly educated, and the groups did not differ in terms of average age (58), years of school, or the percentage of people who carried the APOE-e4 gene, a genetic risk factor for Alzheimer’s disease.
Despite these similarities, the African Americans reported an average of 4.5 stressful events throughout life, compared to just 2.8 reported by white participants. Such experiences were linked to poorer memory and thinking skills for people in both groups, but the effect was magnified for African Americans. In fact, Zuelsdorff said, past adverse events predicted African Americans’ cognitive function more strongly than well-known risk factors like age, education, and genetics.
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"Our findings reaffirm the effect of stress on cognitive health and disparities,” the authors wrote in their study abstract. They emphasize the need for “targeted interventions” to eliminate differences in risk factors across racial groups, and specifically for people in disadvantaged populations.
This isn’t the first study to link stress and cognitive problems, or to suggest that it may raise the risk of dementia. A 2015 study in the journal Alzheimer Disease and Associated Disorders found that adults who perceived themselves to be under the most stress were 30% more likely to have early cognitive impairment, even after accounting for depression symptoms, age, gender, race, education, and genetic risk factors.
Stress can affect hormone levels in the body and reduces the density of nerve cells in the brain, the study authors said at the time. It can also impair immune functioning and may contribute to the development of protein “plaques” in the brain, both of which have been linked to Alzheimer’s development.
But the 2015 findings also suggested that a person's perception of stress may have more influence on future brain health than the actual events themselves, the authors added. That means that finding ways to reduce stress—including cognitive behavioral therapy, meditation and yoga, biofeedback, or even just getting enough sleep—may have a protective effect.