Stressful life events take greater cognitive toll on African Americans than whites

LONDON – African Americans not only report experiencing more stressful experiences across their lifespans than do whites, but they have more cognitive consequences from them as well, new research suggests.

In fact, the weight of these experiences affected cognition even more than traditional risk factors like genetic status and even age, Megan Zuelsdorff, PhD, said at the Alzheimer’s Association International Conference.

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Racial disparities have long been evident in the development and progression of dementia, Dr. Zuelsdorff said. Socioeconomic factors are also important players in this scenario. Stress, likewise, has long been linked to poorer cognitive health. “But, there are still significant gaps in our knowledge of stress and cognition. The contribution of stress to well-established socioeconomic impacts on health is unclear, and the research focus here has always been on events happening in midlife and onward. But, it’s crucial to expand this window of time backward to include earlier years. If we look at a graph of cognitive function across the lifespan, the rate of decline doesn’t vary much. What we do see is that blacks, starting at midlife, are closer to the clinical threshold of cognitive impairment and may reach the threshold at an earlier age. What this said to me is that we needed to look at these earlier life factors that could bring someone to this state of lower cognitive function in midlife.”

Dr. Zuelsdorff and her colleagues analyzed data from the Wisconsin Registry for Alzheimer’s Prevention to examine this question. The observational study comprises 1,500 adults being followed for 15-20 years and is enriched for those with a family history of Alzheimer’s disease. The main goal of WRAP is to understand the biological, medical, environmental, and lifestyle factors that increase a person’s risk of developing Alzheimer’s disease.

Subjects have a study visit every 2-4 years that includes a full physical and cognitive workup. At one visit, Dr. Zuelsdorff said, they were asked to complete a questionnaire concerning 27 different stressful life events. These experiences were deeply disturbing and potentially life altering. They included childhood experiences, such as parental abuse, alcoholism, and flunking out of school, and adult experiences, such as combat experience, bankruptcy, or the death of a child. She then analyzed how the total number of stressful events in a person’s life changed that person’s risk of developing dementia.

Of the entire WRAP cohort, 1,314 completed the stress questionnaire and had sufficient cognitive data. These subjects were largely white (1,232). Only 82 were African American, a weakness of the study, Dr. Zuelsdorff noted, but a reflection of Wisconsin’s racial makeup.

They were similar in a number of important ways, including age (mean, 58 years), proportion of apolipoprotein E4 (APOE4) allele carriers (38%), and years of education (mean, 16). African Americans had higher body mass index (33.3 vs. 28.8 kg/m²), reported less physical activity, were more often current smokers (22% vs. 6%), and had a lower-quality education despite similar time in the classroom.

On average, African Americans reported a mean of 4.5 stressful life events – a significant, 60% increase over the 2.8 reported by whites. The experience of stressful events directly influenced a subject’s performance in the speed and flexibility domain of executive function and in working memory, Dr. Zuelsdorff said.

“We saw a substantial 13.5% attenuation of performance on speed and flexibility, but we also saw attenuation in working memory. That told us something else was going on – that it wasn’t just the accumulation of stressful events but that there was a differential vulnerability. The negative association between lifetime stressful events and the cognitive domains was much stronger in blacks than in whites.”

She then conducted a risk analysis to determine the impact of stress. “Stress was right at the top for blacks. It tended to be one of the most important predictors of cognitive function. The only other one that came out as significant was quality of education. The social environment in this sample was more important than the traditional risk factors of genetics and chronological age.”

The study barely scratches the surface of the stress/cognition conundrum, Dr. Zuelsdorff said. “We would like to look at the timing next and see if there is some critical window that is especially influencing to cognitive health. We then need to target both interventions and effect modifiers, such as social, community, and financial resources that might buffer the effects of this negative stress.”

She had no financial disclosures.

msullivan@frontlinemedcom.com

On Twitter @alz_gal