Researchers Are Figuring Out How African Ancestry Can Affect Certain Brain Disorders

This episode explores the impact of African ancestry on the prevalence and expression of various brain disorders like Alzheimer's, stroke, and Parkinson's.

1. Alzheimer's, stroke, and other brain disorders exhibit differing prevalence rates among racial groups, influenced by genetic ancestry.
2. Parkinson's disease shows a lower incidence in African Americans, potentially due to genetic factors related to inflammation.
3. The research underscores the critical distinction between race (a social construct) and genetic ancestry (biological heritage) in scientific studies.
4. Community engagement and ethical considerations are vital for conducting research in historically marginalized populations.
5. The study sets a precedent for precision medicine, aiming to tailor medical treatment based on individual genetic profiles rather than racial categorization.

1. Introduction to the Topic

Overview of the ongoing efforts to diversify brain science and the unique challenges faced by African Americans in medical research. Insight into how race and genetic ancestry are considered in scientific studies. John Hamilton: "Race is often described as a social construct... Ancestry... is our bloodline."

2. The African Ancestry Neuroscience Research Initiative

Discussion on the formation and goals of the initiative, emphasizing community involvement and the historical context of medical research in African American communities. Kainan Jade Benjamin: "We see these health disparities, which we know are partly to do with environment, but there's also a huge genetic component."

3. Findings of the Study

Detailed explanation of the study's findings, showing how European and African ancestries influence different aspects of brain health and disease susceptibility. Kafwi Zarasa: "Two of those brain cell types that it points to are part of the blood vessels, their lining, and also the cells that deal with inflammation in the brain."

1. Engage with local community leaders and institutions when conducting research involving sensitive genetic information.
2. Educate communities about the importance of genetic diversity in health research.
3. Advocate for the inclusion of diverse genetic backgrounds in large-scale genetic studies to enhance the relevance and applicability of the findings.
4. Support precision medicine initiatives that focus on individual genetic profiles rather than broad racial categories.
5. Encourage open dialogue about the historical misuse of biological data in research to build trust and cooperation.

Black Americans have been underrepresented in most genomic studies of neurological disorders. As a result, scientists don't know much about whether African ancestry affects a person's risk for these disorders or their response to a particular treatment. To help close this gap, the Lieber Institute for Brain Development, African American community leaders in Baltimore, and researchers from Duke University and Morgan State University created the African Ancestry Neuroscience Research Initiative in 2019. The team found that genes associated with African ancestry appear to affect certain brain cells in ways that could increase the risk of Alzheimer's disease and stroke.

People

Kainan Jade Benjamin, Kafwi Zarasa

Content Warnings:

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Emily Kwong
Npr member, FDIC, you're listening to short wave from NPR.

Hey, short waivers. Emily Kwong here with a look at how an effort to diversify brain science has led to a discovery about diseases like Alzheimer's, stroke and Parkinson's. NPR's main brain correspondent John Hamilton has been covering this story. John, hello.

John Hamilton
Hey, Emily. What I've got for you is actually an update on something that you and I chatted about on this podcast several years ago.

Emily Kwong
I remember this conversation, John. We were talking about how Alzheimer's disease seems to be more common in black Americans than in white Americans.

John Hamilton
But nobody knows why exactly the questions are is it the way doctors are assessing symptoms? Is it living conditions? Is it racism? It's all a big mystery. And it's not just about Alzheimer's. We know that stroke and some psychiatric disorders are also more common in black Americans. At the same time, we know Parkinson's disease is less common in black Americans.

So during that episode, I mentioned this community group in Baltimore that is trying to figure out what's causing these disparities.

The group is called the African Ancestry Neuroscience Research Initiative. It was founded in 2019, and just recently I got a chance to learn about the first scientific study to come out of the initiative.

Emily Kwong
Who led the study?

John Hamilton
It was a team effort, like most studies are. But I talked to the lead scientist, whose name is Kainan Jade Benjamin, and he is a researcher at the Lieber Institute for Brain Development and Johns Hopkins University. Here's how he described the thinking behind this new study.

Kainan Jade Benjamin
We see health disparities that are in my community, black american community.

We see these health disparities, which we know are partly to do with environment, but there's also a huge genetic component that also contributes to disease risk. So the idea is, can we tease apart anything that might be influenced by our ancestry, our genetic ancestry.

John Hamilton
But getting to that study involves a huge leap of faith by black families, a lot of cadaver brains, some really elegant genetic analysis, and our country's history of slavery.

Emily Kwong
Today on the show, the links between certain brain disorders and genetic ancestry and.

John Hamilton
How scientists were able to separate a person's ancestry from their racial identity.

Emily Kwong
You're listening to shortwave, the science podcast from NPrDeM.

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Emily Kwong
Okay, John Hamilton, before we get into this research earlier, you were mentioning this difference between race and ancestry. Can you just break down how those things are different?

John Hamilton
Yeah. Well, race is often described as a social construct. It's part of the identity we give ourselves or the way other people see us. But race is really a pretty poor indicator of our biology. You know, what genes we're carrying. Ancestry, on the other hand, specifically genetic ancestry, it's what we might call our bloodline. It's our parents and grandparents and great grandparents. And obviously, ancestry does determine what genes we may be carrying, including the ones involved in diseases.

Emily Kwong
Yeah, I've learned a lot of this from you over the years from Janina Jeff, the geneticist who hosts that incredible podcast in those genes. But given this difference, why would scientists even then use race in a research study?

John Hamilton
In some studies, it's used to help identify groups that are likely to have had different life experiences. But even more than that, a person's self identified race and ethnicity are still one way that our country tracks health disparities.

Sometimes, as we heard Kainan mentioned, those disparities are the result of the environment. So things like where you live, how much you earn, how are you treated. But health problems can also be influenced by genetics. So when researchers see that self identified black Americans are more likely to be diagnosed with Alzheimer's or some other brain disorder, they want to know whether genes might be part of the reason.

Emily Kwong
That makes a lot of sense. Okay, but what do you do, then, in light of the fact that race just doesn't tell you much about a person's genetic background?

John Hamilton
That was exactly the challenge that was facing the scientists who did this study.

Emily Kwong
Right.

John Hamilton
And kindan told me they decided to take this kind of unusual approach.

Kainan Jade Benjamin
Instead of looking at a white population versus black populations, which is the traditional method, we leverage the history of the US to pinpoint in just a black population how european ancestry versus african ancestry affects gene expression in the brain.

Emily Kwong
That's super interesting and also just sounds very complicated to do. So what did it take to turn that idea into a whole scientific study?

John Hamilton
Describe the entire process at length in the journal Nature Neuroscience. That's where the study was published. We will link to it in the show notes for anyone who wants to check it out. The condensed version begins with overcoming a major hurdle to even attempting this study. And that was building trust in the black community.

Emily Kwong
Sure. I mean, there's a lot of reasons that trust is broken. You have history dating back to even before the Tuskegee experiment in Alabama that let black men with syphilis get sicker even after there was a cure.

John Hamilton
Yeah. And keep in mind, Baltimore was the home of Henrietta Lacks. She was a black woman with cancer whose cells were taken by doctors at Johns Hopkins Hospital without her consent. That happened in the 1950s, and those cells, now called hela cells, have been incredibly valuable to researchers ever since. But they've also become a symbol of white doctors and scientists exploiting black patients. So before doing any research, the African Ancestry Initiative and the Lieber Institute teamed up with with black business and church leaders and Morgan State University, a historically black institution in Baltimore. There was a whole lot of community outreach and discussion about how the research they were going to do would be used and who would benefit.

Emily Kwong
That's incredible. And truly the way science should be done.

Right in conversation with the community.

John Hamilton
Exactly. By the way, this initiative also did something interesting. They recruited a brain scientist and psychiatrist at Duke University. His name is Kafwi Zarasa, and his ancestors are from Ghana. He's an MD, PhD, really influential guy, and his area of expertise is research on genes involved in psychiatric disorders like schizophrenia and depression.

Emily Kwong
Oh, interesting. Okay.

John Hamilton
So back when the ancestry initiative was just getting started, I was able to ask Kafui how he got involved, and he told me about a conversation he had with doctor Daniel Weinberger, who is the head of the Lieber Institute.

Kafwi Zarasa
As we were sitting there talking, he mentioned the initiative and then started going through some of the details around the genetics, particularly around what I would say are disturbing aspects of the lack of african ancestry research. And even me, as a researcher had never realized that these large scale studies didn't include folks of african ancestry. And it was clearly and immediately evident to me how much of a problem this was.

Emily Kwong
Okay, I see how this team was formed. So you got the Lieber Institute, you got the brain scientist on board. All of this, ultimately, is to disentangle race from ancestry in the research. After laying all of this groundwork, what went into the physical doing of the study?

John Hamilton
Okay, first they got brain tissue samples from 151 people who had died, many of them from the Baltimore area.

All of those people had identified as black or african american during their lives. And after they died, family members agreed to donate their brains for exactly this sort of research.

Next step was the scientists did a genetic analysis of each person in the study to determine how much of their ancestry was european and how much was african.

It turned out almost every person in the study had a mixture of genes, and some had mostly european ancestry.

Emily Kwong
That doesn't surprise me. I mean, given the legacy of slavery and just how many enslaved people were sexually assaulted.

John Hamilton
Right? I mean, before 1865, that was undoubtedly a factor. And of course, since then, the two ancestries have become increasingly entwined. And that is precisely what allowed Kainin and the other scientists to see how each ancestry influenced the risk for certain brain disorders.

Synchrony Bank
Wow.

Emily Kwong
This is just such incredible research. It takes a lot of courage. What did this team ultimately find?

John Hamilton
One thing they found was that a person's ancestry did not seem to affect the function of neurons. You know, those are the cells responsible for thinking and memory and movement. Instead, Cuffwe told me that the genetic analysis suggested ancestry was a affecting the function of cells involved in the brain's immune system and its blood supply.

Kafwi Zarasa
Two of those brain cell types that it points to are part of the blood vessels, their lining, and also the cells that deal with inflammation in the brain. There are differences there, too, and these differences can be linked to risk for stroke and actually risk for Alzheimer's.

Emily Kwong
Why would these brain cell types be linked to those diseases?

John Hamilton
Stroke involves the lining of the blood vessels. That's where plaques build up and clots form that cause a stroke. So even a really subtle difference in how genes are expressed in these cells could affect a person's risk. With Alzheimer's. There's more and more research suggesting that inflammation is a key part of the process that ultimately leads to the death of neurons. So if a person's genes are making immune cells in the brain react more strongly and cause more inflammation, it could definitely accelerate that disease.

Emily Kwong
Wow. These are some really interesting theories that I imagine could really help with closing gaps in health disparities, caring for these communities better. Okay. When you started talking, John, you mentioned that Parkinson's was also at play. Specifically that black Americans are actually less likely to get Parkinson's than white people. Did the study offer any explanation as to why that is?

John Hamilton
Yes. Parkinson's also seems to be related to inflammation in the brain. And in the study, they found that european ancestry seemed to make a difference. Group of immune cells more reactive. And these cells are found in an area of the brain that's affected by Parkinson's.

Emily Kwong
Okay, we've talked about Parkinson's, about Alzheimer's, about strokes.

I want to talk about other groups.

You know, it's going to take a lot more studies to fully understand how african ancestry influences brain disorders. What about for people of asian ancestry and latino ancestry? What about their genes?

John Hamilton
Yeah, I mean, ancestry is really complicated. You have Latin America and Asia, for instance, and even within those areas, you're going to have many different ancestries break apart.

Emily Kwong
The monolith, John.

John Hamilton
I know, right?

Africa has more genetic diversity than the rest of the world put together. It's amazing.

Scientists really may need to know not just what part of Africa or Asia or South America from, but ultimately, you know, sorting through geography probably won't be the right approach because the world doesn't have that many genetically isolated groups anymore.

Emily Kwong
Right. Genes don't care about boundaries and borders.

John Hamilton
They do not.

Emily Kwong
They just kind of flow.

Synchrony Bank
Yeah.

John Hamilton
And Kafui says that at the moment, he told me he still looks at what his patients say about their racial identity, but he says that is a really flawed approach.

Kafwi Zarasa
The more optimal future is one in which we understand each person's individual genomic architecture and then prescribe medicines based on this. And so I think the future of medicine actually looks a lot like all of us.

Emily Kwong
Oh, John, is cuffweed talking about this thing I've been hearing more about called precision medicine?

John Hamilton
Exactly.

Emily Kwong
It's like personalized medicine.

John Hamilton
Exactly. Right, right. It's this idea that lots of places, including the National Institutes of Health, is pushing really hard.

And it could be the thing that finally moves medical care beyond looking at a patient's race to something that is far more useful.

Emily Kwong
John, I'm completely obsessed with this research. I hope you keep coming back on shortwave to share updates about it. Thank you so much.

John Hamilton
I'll be back. Emily.

Emily Kwong
Before we head out, a quick shout out to our short wave plus listeners. We appreciate you and we thank you for being a supporter. Shortwave plus helps support our show, and if you're a regular listener, I think it's time for you to join so you can enjoy the show without sponsor interruptions. Wouldn't that be nice? Find out more at plus dot npr.org shortwave.

Today's episode was produced by Rachel Carlson. It was edited by our showrunner Rebecca Ramirez and fact checked by John Hamilton. The audio engineer was Kwesi Lee. Beth Donovan is our senior director and Colin Campbell is our senior vice president of podcasting strategy. I'm Emily Kwong. Thank you for listening to short wave from NPR.

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