African Americans most at risk for brain aging

Stressful events and living conditions increase risk of dementia as we age

Studies at the 2017 Alzheimer’s Association International Conference, held in London, highlight racial disparities in dementia risk and incidence.

They confirm racial inequities in numbers of people with Alzheimer’s disease and other dementias — even after age 90 — and also point to growing evidence that early life stress and neighborhood conditions contribute to dementia risk in late life.

One new study in Wisconsin found that a single major stressful event in early life is equal to four years of cognitive aging, and African Americans are most at risk. On average, they experience over 60 percent more of such events than non-Hispanic Whites over their lifetimes.

A second study conducted by a health plan in Northern California found that African Americans born in states with the highest levels of infant mortality had 40 percent increased risk of dementia compared to African Americans not from those states, and 80 percent increased risk compared to Whites not from those states.

Additional study findings

Racial disparities in the risk for new cases of dementia previously observed in the younger elderly continue into the oldest-old (age 90+), which is the fastest-growing segment of the population. Researchers found oldest-old African Americans and Latinos had the highest incidence rates compared to Asian Americans and Whites, matching the overall patterns of racial/ethnic disparities in dementia seen in younger elderly.

Neighborhood disadvantage may contribute to observed disparities in prevalence of dementia. “These studies were done with U.S. data, but they add weight to the global body of evidence around disadvantage and dementia risk, which is an issue governments around the world grapple with, and one that requires coordinated action,” said Maria C. Carrillo, Ph.D., Alzheimer’s Association chief science officer.

There are marked differences in rates of dementia by racial/ethnic groups, showing increased rates for African Americans and decreased rates for Asian Americans. For all adults 65 and older, African Americans are about twice as likely to have Alzheimer’s or other dementias as older Whites and Hispanics are about one and one-half times as likely to have Alzheimer’s or other dementias as older Whites.

Lifetime stressful experiences worsen memory and thinking more strongly in African Americans. Prevalence of Alzheimer’s disease and cognitive impairment is rising, and the greatest burden seems to be falling disproportionately on historically disadvantaged communities.

Megan Zuelsdorff, Ph.D., at the University of Wisconsin School of Medicine and Public Health, and colleagues examined the impact of lifetime stressful experiences on cognition. The goal was to understand how stressful experiences such as being fired from a job, the death of a child, growing up with a parent who abused alcohol or drugs, or experiencing combat impacted cognition differently in these two groups.

Stressful experiences included educational difficulties, interpersonal conflicts, financial insecurity, legal and justice system issues, serious health events and psychosocial or physical trauma.

A greater number of stressful events was associated with poorer late-life cognitive function for all study participants. Even within a relatively small, highly educated sample, African Americans experienced over 60 percent more stressful events than non-Hispanic Whites during their lifetimes, and these experiences were linked to poorer memory and thinking skills in older age.

High infant mortality rates are a marker of adverse social and physical conditions, and birth in areas with high infant mortality rates are associated with a variety of poor health outcomes. African Americans born in high infant mortality states had almost 80 percent greater risk of dementia even after accounting for education and health risk factors, compared to Whites born outside high infant mortality states. Being born in a high infant mortality state was not associated with dementia risk among Whites.

“This is the first study of place of birth and long-term dementia risk,” Paola Gilsanz, ScD, of the University of California, said. “African Americans born around 1928 were likely exposed to harsher early life conditions that may have increased their risk of dementia later in life. Our findings suggest that differences in early life conditions may contribute to racial inequalities in dementia rate, and they point to growing evidence that early life conditions contribute to dementia risk in late life.”

Living in a disadvantaged neighborhood may also increase Alzheimer’s disease risk. Disadvantaged neighborhoods often pose barriers for accessing healthy foods, safe exercise options, toxin-free environments, and other factors that impact health. It is known that living in a disadvantaged neighborhood increases risk of diabetes, cancer, and early death, and that moving to less disadvantaged settings improves health.

Researchers found that people in the most disadvantaged neighborhoods had markedly worse cognitive performance in all aspects measured (working memory, immediate memory, speed and flexibility of cognition, and verbal learning), even after adjusting for age and education.

“This study provides evidence to suggest that living in a neighborhood challenged by poverty, low education, unemployment, and/or substandard housing may increase risk of Alzheimer’s disease, and may account for some of the observed differences in Alzheimer’s disease risk among people of different racial backgrounds and income levels,” said Amy Kind, MD, PhD, of the University of Wisconsin School of Medicine.

 

— Information provided by the 2017 Alzheimer’s Association International Conference. For further information, visit the AAIC 2017 home page: www.alz.org/aaic.