Despite Higher Alzheimer’s Risk, Black and Latinx Americans Less Likely To Test Positive on Amyloid PET

Black and Latinx Americans are at an elevated risk of Alzheimer’s and dementia. But they face diagnostic delays, are underrepresented in research trials, and are far less likely to access  disease-modifying therapies for Alzheimer’s, such as Leqembi and Kisunla. 

Researchers wanted to know if the rates of testing positive on a gold-standard test for confirming Alzheimer’s differed among these racial and ethnic groups, contributing to these disparities. 

A study recently published in Alzheimer’s & Dementia followed more than 5,700 cognitively impaired Americans, including more than 22 percent who were Black and 20 percent who were Latinx — which includes Hispanic, Latino, and other ethnicities whose histories trace back to South America. Each individual received an amyloid PET scan, a gold-standard brain imaging method for measuring the levels of Alzheimer’s-associated beta-amyloid plaques in the brain. 

Dr. Consuelo Wilkins, a professor of medicine at Vanderbilt University who led the study, told Being Patient that participants who were Black or Latinx may have other diseases like vascular dementia that may mean developing Alzheimer’s symptoms at a lower level of beta-amyloid.

A real-world study of amyloid PET

The researchers wanted to see what amyloid PET positivity looked like in the real world. Rather than providing scans for free, they recruited participants with Medicare or Medicare Advantage plans being seen by a dementia specialist as part of their usual care. This allowed Wilkins and her colleagues to study real-world differences in amyloid PET positivity and the challenges people face when seeking a diagnosis.

The researchers split the participants into three groups: Black, Latinx, and all other races and ethnicities. The latter group was mostly white but also Asian and Indigenous individuals.

Black participants were 28 percent less likely to have a positive amyloid PET scan, while those who were Latinx were 22 percent less likely, even after researchers accounted for age, sex, and other factors. 

Susan Landau, a neuroscientist at the University of California, Berkeley, who wasn’t involved in the study, told Being Patient that the study is a “very important contribution” toward understanding how these biomarkers may differ in Black and Latinx individuals.

The researchers also looked at where the participants lived to see whether where an individual lived might influence their Alzheimer’s risk. Those who lived in the most prosperous areas were least likely to have a positive amyloid scan. Other social determinants of health did not affect the likelihood of a positive scan. 

In the study, Black and Latinx participants were also over 2.5 times as likely to be enrolled in a Medicare Advantage plan, where participants encountered challenges obtaining authorization from insurance to pay for the scans, even though they should be covered under Medicare. 

“I know there are some people who are really big fans of Medicare Advantage, but they are known to be predatory,“ said Wilkins. While they cover some extra like supplements, these plans require people to jump through hoops for “complex diagnostics or specialized treatments,” requiring more approvals before providing coverage. 

Filling in the knowledge gaps

Understanding the prevalence of amyloid positivity across ethnoracial groups is important since  individuals from under-represented ethnoracial groups have been disproportionately excluded from clinical trials that screen for participants through these scans.

“Some have suggested race-specific amyloid positivity thresholds may address this problem,” said Landau, “but amyloid positivity thresholds are designed to be a direct measure of underlying pathology,” and other research has found that the threshold for positivity is constant across ethnic and racial groups.

These differences might be driven by other conditions that may cause cognitive impairment. “My hypothesis which is not proven yet,” said Wilkins, “is that these groups have more mixed pathology.” 

It’s common for people to develop multiple protein plaques, aggregates, and pathologies as they age, and perhaps this extra disease makes the brain more vulnerable to beta-amyloid even at lower levels. Other factors, she said, like living conditions and experiencing racism or discrimination, may act as a stressor and impact cognition. 

Still many of these groups continue to be underrepresented in research, and sociodemographic factors are seldom reported. 

“We really have to push research to make sure that they’re including equity in the rigor,” said Wilkins. “You know there are certain populations that have a greater burden of the disease, then why aren’t you one, making sure you have those people in your study.”