Researchers Explain Why Black Americans Are at Higher Risk for Alzheimer's

OPRAH MAGAZINE
Jun 24, 2020
By Meghan Rabbitt

The Alzheimer’s epidemic no one is talking about.
 

Six years ago, Veronica Shanklin showed up at her childhood home in DeSoto, Texas, expecting a typical visit. Shanklin’s grandmother, who’d been diagnosed with Alzheimer’s disease at age 82, had moved in with Shanklin’s mom a few years earlier. Shanklin, a marketing executive in Chicago, wanted to spend some time with them and was also eager to help with caretaking for a few days; she was sure her mom, then 66, could use a break.

Yet mere minutes after walking in the door, Shanklin’s heart sank. Both her grandmother and mother had lost weight. The usually tidy home was a mess, with dirty laundry piling up and overdue bills scattered across a bed.

“My mom was the manager of the credit union at her church,” Shanklin says. “If she couldn’t pay her own bills or keep up with cooking and cleaning, I knew something was wrong.” Then Shanklin noticed that her mother kept forgetting what day it was. She’d seen her grandmother—and grandfather, who also had Alzheimer’s—deal with similar issues. Worried, Shanklin took her mom to the doctor. The diagnosis confirmed her fear: Alzheimer’s disease.

Shanklin quit her job and moved to Texas. She took over caregiving for her mother and grandmother—preparing meals, keeping house, helping them get to doctor’s visits—all while making sure they didn’t wander out of the house or otherwise endanger themselves. “This disease has turned my life upside down,” Shanklin says. “And the fact that it’s touched two of my grandparents and my mom almost seems unfair.”

Unfair, yes, but unfortunately not unusual. Shanklin’s family history is in line with
some staggering statistics: Older African Americans are about twice as likely as older non-Hispanic white people to develop Alzheimer’s or other dementias, according to the Alzheimer’s Association. On top of that, less than 5 percent of participants in U.S. health studies are black, making it difficult to identify factors driving the disparity and find ways to address them.

Scientists have tried to ascertain whether African Americans naturally make more beta-amyloid and tau proteins, two of the signature causes of Alzheimer’s. Beta-amyloid forms clumps in the brain that interfere with cell-to-cell communication, and tau creates so-called tangles inside brain cells. Both result in forgetfulness, confusion, difficulty concentrating, delusions, and other telltale symptoms of the disease. So far, there’s no evidence that African Americans have higher levels of beta-amyloid or tau, says Reisa A. Sperling, MD, a Harvard Medical School neurology professor and director of the Center for Alzheimer Research and Treatment at Brigham and Women’s Hospital.

“We have other theories, though,” says Lisa L. Barnes, PhD, a professor of gerontology and geriatric medicine at the Rush Alzheimer’s Disease Center at Rush University Medical Center and a trailblazer in researching the Alzheimer’s racial imbalance. Barnes and other experts point to the fact that Black Americans have higher rates of diabetes, hypertension, stroke, elevated cholesterol, and heart disease—all of which are correlated with Alzheimer’s dementia. These conditions also affect blood vessels and can impair blood flow, which can then damage the brain and may also contribute to beta-amyloid and tau protein buildup, thereby raising Alzheimer’s risk, explains Barnes.

On top of that, “diabetic brains have difficulty utilizing and managing glucose and have more difficulty making new brain cells,” says Goldie S. Byrd, PhD, professor and director of the Maya Angelou Center for Health Equity at Wake Forest School of Medicine. All of these issues can lead to memory impairment, cognitive and behavioral changes, and other signs of Alzheimer’s, she says.

In a 2015 study, Barnes and colleagues compared brain autopsies of black and white Alzheimer’s patients who had similar backgrounds (age, sex, education level, and cognitive ability). They found that the Black patients were more likely to have “mixed brain pathologies”—meaning that in addition to the expected signs of Alzheimer’s (beta-amyloid and tau proteins), they had conditions like arteriosclerosis and atherosclerosis, two forms of vascular disease.

Even when scientists control for cardiovascular and related factors, however, Black Americans are still more susceptible to Alzheimer’s and other dementias. A 2017 JAMA Neurology study found that those born in states with high stroke death rates (Alabama, Alaska, Arkansas, Louisiana, Mississippi, Oklahoma, South Carolina, Tennessee, and West Virginia) had a 67 percent higher risk for dementia compared with non-Black participants born elsewhere, while non-Black subjects born in those states faced a 46 percent increased risk. “A theory holds that older African Americans who were exposed to segregation, which was prevalent in many of these states, experienced significant long-term stress, which could possibly contribute to a decline in cognitive function later in life,” says Rachel Whitmer, PhD, a principal investigator on the study and professor and associate director of the Alzheimer’s Disease Research Center at UC Davis School of Medicine.

A growing body of research is exploring the links between long-term stress and racial discrepancies in dementia. Among other things, chronic stress contributes to inflammation and vascular disease, and can even directly damage the brain’s neurons. “This can lead to a slew of health issues, including atrophy in areas of the brain that are key for memory and cognition,” says Megan Zuelsdorff, PhD, an assistant professor at the University of Wisconsin-Madison School of Nursing investigating the mechanisms underlying cognitive health and dementia disparities.

A recent study coauthored by Zuelsdorff found that stressful life events (financial insecurity, legal issues, divorce, being fired from a job, the death of a child) took a greater
toll on the memory function of African Americans. For white participants, each stressful event was equivalent to about six additional months of normal aging; in Black participants, each of the same stressors added an additional year and a half. The study also found that African Americans reported 84 percent more stressful life events than their white counterparts.

Stressful events not only have residual effects but can also add up over time. “When you’re dealing with a stressor or a challenging life situation, your physical, social, and financial resources can become depleted, making you more vulnerable to the next hit,” says Zuelsdorff. “Since disadvantage—economic, educational, societal—can be cumulative, we think it could be one reason for theAlzheimer’s disparity.” One of Barnes’s studies shows a direct link between the specific stress of discrimination and poor cognitive function, particularly memory. “We need more research in this area,” says Barnes.

That’s where the work of Jennifer J. Manly, PhD, a professor of neuropsychology at Columbia University Irving Medical Center, comes in. When Manly and colleagues compared results of memory tests of African Americans and white Americans who had received the same quality of childhood education, they found no difference in the rate of cognitive decline over time. In other research, they found a decreasing trend of dementia among African Americans who benefited from access to more schooling and better education. There is hope that widespread legal and cultural intolerance for discrimination will eventually help even out risk levels. “Thanks to increasing educational equality, we believe there’s a good chance that we won’t see this disparity in the future,” says Whitmer.

Shanklin, too, is looking toward then future—hers and that of other Black people. Her grandmother died in 2017, and her mother’s short-term memory has worsened. To try to avoid a similar fate, Shanklin eats healthfully and exercises regularly, habits that research has shown may help delay cognitive decline. She started a nonprofit, Dementia Care Warriors, that offers support to caregivers and signed up with the Alzheimer’s Association to be considered for related studies (see “Get Involved”). “Watching someone you love battle Alzheimer’s can make you feel helpless—and mad, considering African Americans are so much more affected,” she says.“I want to do whatever I can to help experts find the answers we need.”