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LONDON -- African Americans had more stressful life events than whites, and that may have driven worse cognitive outcomes in the long run, researchers reported here.

In an analysis of data from the Wisconsin Registry for Alzheimer's Prevention (WRAP) study, black patients had significantly more stressful life events than whites (4.5 vs 2.8, P<0.001), reported Megan Zuelsdorff, PhD, of the University of Wisconsin in Madison, and colleagues at the Alzheimer's Association International Conference.

As stressful life events increased, blacks had worse outcomes on tests of executive function compared with whites, Zuelsdorff said.

"That differential exposure is really important," Zuelsdorff said during a press briefing. "In African Americans, the negative relationship between stressful life experiences and cognitive function was much stronger than in whites."

However, she noted that the sample of more than 1,000 patients was predominantly white, with only 82 African Americans, so it's "important to take that small number into account when interpreting the results."

Research has shown that stress is tied to worse health outcomes later in life, including poor cognitive function, and could be greater among those with lower socioeconomic status.

Zuelsdorff noted that the rate of decline isn't different between whites and blacks; rather African Americans start experiencing poor memory and cognitive health declines earlier. "They're starting closer to clinical levels of impairment, and as such, they may reach those impairment thresholds earlier even if they're experiencing the same, or even slowed, rates of decline as someone who starts at higher level of health in early to mid-life."

"What this says to me is that it's important to look back at earlier life and explore the factors that bring someone to a higher versus a lower cognitive health level in midlife, and we looked at stressful experiences as one such factor," she said.

Zuelsdorff's group assessed 1,314 patients in the WRAP study who had completed questionnaires on stressful life experiences. They also had cognitive testing. Their mean age was 58.5, mean years of education was 16, and APOE4 carrier status didn't vary by race. The researchers also noted that while the quantity of education didn't differ between groups, the quality of education was lower among African Americans.

The questionnaire asked about 27 stressful life events, including divorce, assault, bankruptcy, and losing a child. Researchers performed two tests for executive function -- working memory and speed/flexibility -- and four memory tests: verbal learning and memory, immediate memory, visual learning and memory, and story recall.

In the overall sample, stressful life experiences were associated with poorer results on the executive function test of speed/flexibility, the researchers reported. There was no relationship with working memory.

When looking at the results by race, a greater number of stressful life experiences was associated with greater cognitive detriment among African Americans than whites on both domains of executive function, working memory and speed/flexibility, the researchers reported.

The differences in stressful life events experienced between blacks and whites is not inconsequential given that each event is equivalent to 4 years of cognitive aging, Zuelsdorff said. "That's not a small deal when you're talking about four or five of these [stressful life events] on average."

She acknowledged that the data need to be replicated in a larger state sample and in a larger national sample. Also, "mitigating factors" such as social and community resources that "soften the negative impact of stress on cognition" need to be explored.

Press briefing moderator Mary Sano, PhD, of Mount Sinai Hospital in New York City, said it's known that stressful life events have an impact on cognition, and are a "major risk factor for dementia."

"We know there are more of these evens among African Americans, and we know the impact on this cohort is even greater," Sano said. "This is a double whammy -- a higher number of stressful events as well as worse outcomes from these stressful events -- on the risk of dementia."

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