Black Americans are nearly twice as likely as their white counterparts to develop dementia and also face some of the highest obesity rates in the nation — troubling numbers as St. Louis researchers say the two conditions may be more closely connected than once believed.
New findings from Dr. Cyrus Raji and his team at Washington University School of Medicine suggest obesity — long known to increase the risk of heart disease and diabetes — may also play a significant role in accelerating cognitive decline, raising urgent questions about prevention and health equity in communities already disproportionately affected by both conditions.
More than 7 million Americans are living with Alzheimer’s disease, the most common form of dementia, and that number is expected to climb sharply in the coming decades, according to the Alzheimer’s Association. In St. Louis, where the African American population is roughly 45% to 50%, the stakes are particularly high.
“Our lab is about trying to optimize brain health,” said Raji, associate professor of radiology at Washington University. “Anything you can do to optimize all the different functions” of the brain and body matters, he said.
Raji leads a lab in the Neuroimaging Labs Research Center at WashU Medicine Mallinckrodt Institute of Radiology, which focuses not only on diagnosing Alzheimer’s disease, but also on understanding the broader health factors that may shape who develops it — and when.
“You look at all the risk factors (for Alzheimer’s disease) — traumatic brain injury, depression, smoking, low educational attainment, air pollution,” he said. “Obesity is the most common one. If we can modify these risk factors, we can cut the burden of dementia.”
Raji’s research focuses on visceral fat, which is stored deep in the abdomen around internal organs and is more closely tied to diabetes, cardiovascular disease and metabolic dysfunction.
The WashU team uses abdominal MRI scans to measure visceral fat and compares those findings with brain imaging and PET scans that detect early Alzheimer’s-related changes.
“The brain pathology develops 20 to 25 years before the symptoms show up,” Raji said. “We have been able to identify the earliest link between obesity, particularly visceral obesity, and Alzheimer’s pathology in individuals who are completely presymptomatic.”
Multiple studies have linked visceral fat to chronic stress. A 2025 study published in Alzheimer’s & Dementia found that structural racism, economic hardship, lower educational attainment and reduced access to health care contribute to higher risk and faster progression of dementia among Black residents in St. Louis.
Jill Cigliana, executive director of Memory Care Home Solutions, works with families caring for loved ones living with dementia by providing programs and access to resources.
“Families may come to us with or without a diagnosis, and we know African Americans are about 35% less likely to be diagnosed than their white counterparts,” she said. “What we often do is help people understand what dementia is, what the typical signs and symptoms are, and the functional changes and behaviors. We help link them with health care providers who can provide a clearer diagnosis.”
Raji’s preliminary findings also show that neighborhood disadvantage correlates with changes in certain brain biomarkers. The lab is expanding its work to gather more detailed data on childhood adversity, chronic stress and life-course factors to better understand how social conditions influence dementia risk.
“African American communities, particularly in the St. Louis area, have a higher risk of being located in food deserts, where proper nutrition and resources are not readily available,” Raji said. “It was very important that we factored that into consideration.”
Raji’s team measures neighborhood disadvantage to examine how environment and health intersect. In St. Louis, the stark divide along Delmar Boulevard illustrates how geography can shape opportunity, access to food and long-term health outcomes.
A critical dimension of Raji’s work is representation. Black Americans, he noted, remain significantly underrepresented in brain imaging research.
“African Americans comprise only about 7% of participants in studies using brain imaging to understand diseases of the human brain,” he said. “In the field of Alzheimer’s therapeutics, only about 2% of participants in clinical trials are African American.”
Senior research coordinator LaKisha Lloyd said building trust among research participants is essential — particularly in African American communities, where longstanding mistrust is rooted in unethical medical research practices.
Those include the Tuskegee syphilis study, the use of Henrietta Lacks’ cells without her consent and the use of enslaved Black women to test early gynecological methods without anesthesia.
“With recruiting participants for any research study — whether Alzheimer’s or mental health — you have to gain the trust of the people you’ll be working with,” Lloyd said. “I tell participants I would never ask them to do anything I wouldn’t do myself.”
Lloyd said she and some of her family members participate in brain imaging research.
Raji believes the window for prevention opens decades before memory loss begins.
“If you can understand the risk factors that early, you’re more likely to develop interventions that can help prevent the disease in the future,” he said.