Some minorities more likely to have dementia but less apt to signal so on PET imaging

Some racial and ethnic minorities are more likely to have dementia but less likely to signal so on PET (positron emission tomography) imaging, according to new research. 

In particular, Black and Hispanic individuals—known to be at greater risk of developing the degenerative disease—are significantly less apt than others to show Alzheimer’s pathology on brain imaging. The finding comes from a new study of nearly 5,800 Medicare beneficiaries nationwide, who had mild cognitive impairment or dementia at the time. 

Experts with Vanderbilt University, which led the investigation, believe their findings may indicate differing causes of dementia symptoms may drive downstream diagnosis and treatment disparities. 

“We need desperately to combat the scourge of Alzheimer’s, but our results highlight that a fixation on Alzheimer’s pathology, to the exclusion of other causes of dementia, could inadvertently worsen stark ethnoracial health differences,” corresponding author Consuelo Wilkins, MD, a professor of rural health and geriatric medicine at the Nashville, Tennessee-based institution, said in a statement May 27. “Our findings urge further study,” she added.

For their investigation, published Wednesday in Alzheimer’s and Dementia, researchers analyzed differences in amyloid PET positivity by ethnicity and race. The final Medicare sample was approximately 22% Black subjects and 20% Hispanic, while the remaining 58% including all other races/ethnicities. Amyloid plaques in the brain, identified using PET nuclear imaging, are a hallmark of Alzheimer’s disease, accounting for 60% to 80% of dementia, experts note. However, people who develop other forms of the disease may lack these plaques altogether. 

Among the study sample, Wilkins and colleagues found lower odds of amyloid positivity in both Black (28% lower) and Latinx (22%) patients compared to all other races and ethnicities. Individuals in “comfortable” and “distressed” Area Deprivation Index groups also had greater odds of amyloid positivity than individuals in the “prosperous” group, the study found. (ADI is a neighborhood-level metric ranking areas by socioeconomic disadvantage.) Wilkins and colleagues divided ADI into quintiles including prosperous (the lowest AD), to comfortable, mid-tier, at risks and distressed (the highest). 

Compared to all other races and ethnicities, Black and Hispanic participants also were more likely to present at a dementia stage rather than with mild cognitive impairment. They also were more than twice as likely to be enrolled in Medicare Advantage, which the authors linked to access-to-care barriers. Odds of amyloid positivity in comfortable and distressed areas were 22% and 40% higher, respectively, than in prosperous ones. Meanwhile, PET positivity odds in mid-tier and at-risk areas did not differ from those in prosperous ones. The study found no significant differences in positivity odds when comparing across gender, educational attainment or type of Medicare coverage. 

One of the key takeaways for study co-author Corey Bolton, PsyD, an assistant professor of geriatric medicine at Vanderbilt: “Among people with cognitive impairment, normal PET results may lessen treatment access and clinical trial eligibility,” he said in the announcement. “Our results confirm that these disadvantages are apt to fall inordinately on Black and Hispanic people.”

Experts emphasize that the results highlight the need for other non-amyloid interventions for the treatment and prevention of cognitive decline. The study was funded by the American College of Radiology, the Alzheimer’s Association, Avid Radiopharmaceuticals, GE HealthCare, Life Molecular Imaging and the National Institutes of Health.