Research shows that there is a disproportionate risk for Alzheimer’s disease (AD) among some groups of people. Women, people living in rural communities, people of color, and people experiencing socioeconomic disadvantages are all more likely to develop AD. By studying these risk differences, researchers gain valuable insights to better understand the disease and interventions that can reduce risk. Recently, researchers at the University of Wisconsin-Madison found that a stress-related pathway contributes to cognitive aging and may disproportionately affect African Americans. This research was published in January 2020 in the Journal of Alzheimer's Disease, "Stressful Life Events and Racial Disparities in Cognition Among Middle-Aged and Older Adults."
The lead researcher, Megan Zuelsdorff, PhD, is an assistant professor in the UW School of Nursing and a faculty affiliate in the Wisconsin Alzheimer’s Disease Research Center (ADRC). She runs the Wisconsin ADRC's Stress and Resilience in Dementia (STRIDE) study.
Using self-reported data provided by participants from the Wisconsin Registry for Alzheimer’s Prevention (WRAP), Zuelsdorff and her team considered health history, psychosocial factors, lifestyle, blood samples, clinical data, and neuropsychological tests. They found that people who reported experiencing more stressful life events performed more poorly on cognitive tests regardless of race. They also found that African Americans are disproportionately exposed to stress, which may increase their risk for age-related cognitive impairments.
The WRAP study asked about different stressful life events across the lifespan, including events like involuntary unemployment and death of a child. Participants’ reported stressful life events were composed into a life event index score. Compared to their White counterparts, African Americans reported experiencing significantly more stressful life events, with a nearly 84% higher mean number of stressful life events.
In the African American group, the researchers found negative associations between life event index scores and performance on tests that measure speed and flexibility skills, and the rate of change over time on a test of verbal memory. They found no associations between life event index scores and test performances in Working Memory domains. In the White group, they found a negative association only between life event index scores and performance on speed and flexibility.
The study's findings that stressful life events are linked to poorer speed and flexibility and, in African Americans, faster declines in memory, may be consistent with phenomenon called “weathering.” Weathering describes the early aging of the body and brain that can occur when accumulating hardship in life causes dysregulation in the body’s immune and vascular systems, and premature onset of age-related disease including brain and memory changes. Stress may also lead to poorer sleep and symptoms of depression, which can also impact cognitive test performance.
It was surprising to the researchers that stressful life events were not associated with Working Memory performance in either group. The authors theorize it may be a result of the small number of African Americans in the study. Working Memory has also been shown in previous studies to have a strong genetic component among White WRAP participants, so may be less influenced by modifiable factors like stress.
Zuelsdorff and her team show that social conditions are likely to be important in determining risks for cognitive aging and the higher rates of dementia that burden communities of color. This research is one of the first studies examining stress and cognitive aging in African Americans. It provides a foundation for future studies that will explore whether similar pathways are responsible for higher dementia risk in rural or socioeconomically struggling populations, as well as the protective factors that help individuals cope with stressful events. As a result of the COVID-19 crisis, Wisconsin communities are facing immense physical, psychological, and financial hardships. Understanding stress-related cognitive risk, and how its impact can be reduced by individual and community resources, will be a crucial area of study.
Learn more about Dr. Zuelsdorff's research in this "Dementia Matters" podcast episode from our archives, "Connecting Lifetime Stress to Brain Health."
Story by Kaitlin Edwards
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