African Americans may be twice as likely to develop Alzheimer’s than their white peers – and yet they are less likely to be diagnosed.
That’s according to a new study that reveals fresh clues about what could be driving the gaps in disease rates and diagnoses.
The study of 1,215 people showed black people have lower levels of the protein called tau in their blood, which is normally a good sign because it tends to fuel build-ups in the brain.
In fact, African Americans with the high-risk gene APOE4, which is strongly associated with Alzheimer’s, actually had lower levels of tau.
It seems that something else may drive the disease in African Americans, which could be more aggressive than the way tau manifests.
However, experts warn we are struggling to solve the mysterious gap because most of our Alzheimer’s studies have been performed on white people and the medical community’s understanding of black bodies is much more limited.
Researchers found white Alzheimer’s patients have much higher levels of tau in their blood. But that is not the case for African Americans. And yet, rates are higher for blacks (file image)
‘If we only study Alzheimer’s in Caucasians, we’ll only learn about Alzheimer’s in Caucasians,’ said John C. Morris, MD, the Harvey A. and Dorismae Hacker Friedman Distinguished Professor of Neurology at Washington University, St Louis.
‘If we want to understand all the ways the disease can develop in people, we need to include people from all groups. Without a complete understanding of the illness, we’re not going to be able to develop therapies that work for all people.’
In Dr Morris’s study, published in JAMA Neurology, 14 percent (173) of the participants were African American – close to the local rate in St Louis, where 18 percent of Alzheimer’s diagnoses are in black people.
The average age was 71 years old.
A third of the participants had mild Alzheimer’s, while two thirds had no memory loss or confusion symptoms.
They all either underwent a PET scan to see build-ups of toxic amyloid protein in their brains, an MRI scan to see brain shrinkage, or a spinal tap to see proteins in their blood.
Using the MRI and PET scans, they were able to identify patients’ disease state, and there were no clear differences between races.
However, the blood samples were all off for the African American patients.
Tau levels were elevated for Alzheimer’s patients regardless of their race.
However, in African American patients the levels were much lower – to the extent that they wouldn’t normally class as concerning.
‘What this may indicate is that the cutoffs between normal and high levels of tau that were developed by studying whites are probably not accurate for African-Americans and could cause us to miss signs of disease in some people,’ Dr Morris said.
His team believe the Alzheimer’s gene APOE4 may function differently in different races.
They found that African Americans with APOE4 had a higher risk of Alzheimer’s, but they were more likely to have low levels of tau.
Conversely, people who carried the low-risk forms of the gene, tau levels were similar, regardless of race.
‘It looks like the APOE4 risk factor doesn’t operate the same in African-Americans as it does in whites,’ Dr Morris said.
‘We need to start looking into the possibility that the disease develops in distinct ways in various populations. People may be getting the same illness – Alzheimer’s disease – via different biological pathways.’
He called on the medical community to dig deeper into these differences with research and trials including all races.
‘We’ve been focusing on African-Americans because we have a large African-American community here in St. Louis, but we also need Asian-Americans, Native Americans, Hispanics, everybody to participate in research,’ Morris said.
‘I think we’ll find we’ve been missing a lot by having such limited study populations in the past. We need to find out what else is going on, so we can develop better therapies that apply to everyone.’