Researchers are figuring out how African ancestry can affect certain brain disorders
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EMILY KWONG: You're listening to Short Wave from NPR. Hey, Short Wavers, 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 Jon Hamilton has been covering this story. Jon, hello.
JON 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.
KWONG: I remember this conversation, Jon. We were talking about how Alzheimer's disease seems to be more common in Black Americans than in white Americans, but nobody knows why.
HAMILTON: Exactly. The questions are, is it the way doctors are assessing symptoms? Is it living conditions? Is it racism?
KWONG: Yeah.
HAMILTON: 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.
KWONG: Who led the study?
HAMILTON: It was a team effort, like most studies are. But I talked to the lead scientist, whose name is Kynon 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.
KYNON JADE BENJAMIN: We see health disparities that are in my community and 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?
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.
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KWONG: Today, on the show, the links between certain brain disorders and genetic ancestry.
HAMILTON: And how scientists were able to separate a person's ancestry from their racial identity.
KWONG: You're listening to Short Wave, the science podcast from NPR.
KWONG: OK, Jon 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?
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, is 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.
KWONG: Yeah, I've learned a lot of this from you over the years, from Janina Jeff, the geneticist who hosts that incredible podcast, inthosegenes. But given this difference, why would scientists even then use race in a research study?
HAMILTON: In some studies, it's used to help identify groups that are likely to have had, you know, 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.
KWONG: Oh, OK.
HAMILTON: Sometimes, as we heard Kynon mention, 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.
KWONG: That makes a lot of sense, OK. 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?
HAMILTON: That was exactly the challenge that was facing the scientists who did this study.
KWONG: Right.
HAMILTON: And Kynon told me they decided to take this kind of unusual approach.
BENJAMIN: Instead of looking at a white population versus Black populations, which is the traditional method, we leveraged the history of the US to pinpoint in just a Black population how European ancestry versus African ancestry affects gene expression in the brain.
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?
HAMILTON: Yeah, they described 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.
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.
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.
KWONG: Yeah.
HAMILTON: So before doing any research, the African Ancestry Initiative and the Lieber Institute teamed up 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.
KWONG: That's incredible. And truly the way science should be done, right? In conversation with the community.
HAMILTON: Exactly. By the way, this initiative also did something interesting. They recruited a brain scientist and psychiatrist at Duke University. His name is Kafue Dzirasa, 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.
KWONG: Oh, interesting. OK.
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 Dr. Daniel Weinberger, who is the head of the Lieber Institute.
KAFUI DZIRASA: 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.
KWONG: OK, 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?
HAMILTON: OK, 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. The 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.
KWONG: That doesn't surprise me, I mean, given the legacy of slavery and just how many enslaved people were sexually assaulted.
HAMILTON: Right. I mean, before 1865, that was undoubtedly a factor. And of course, since then, you know, the two ancestries have become increasingly entwined. And that is precisely what allowed Kynon and the other scientists to see how each ancestry influenced the risk for certain brain disorders.
KWONG: Wow, this is just such incredible research. It takes a lot of courage. What did this team ultimately find?
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, Kafui told me that the genetic analysis suggested ancestry was affecting the function of cells involved in the brain's immune system and its blood supply.
DZIRASA: 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.
KWONG: Why would these brain cell types be linked to those diseases?
HAMILTON: Well, stroke, you know, 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.
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. OK, when you started talking, Jon, 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?
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 different group of immune cells more reactive. And these cells are found in an area of the brain that's affected by Parkinson's.
KWONG: OK, 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?
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.
KWONG: Break apart the monolith, Jon. There's so many different groups.
HAMILTON: I know, right? It's like, you know, Africa has more genetic diversity than, like, the rest of the world put together. It's amazing. So scientists really may need to know not just what part of Africa or Asia or South America you're 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.
KWONG: Right, genes don't care about boundaries and borders.
HAMILTON: They do not.
KWONG: They just kind of flow, yeah.
HAMILTON: And Kafui says that at the moment, you know, he told me he still looks at what his patients say about their racial identity, but he says that is a really flawed approach.
DZIRASA: 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.
KWONG: Oh, Jon, is Kafui talking about this thing I've been hearing more about called precision medicine?
HAMILTON: Exactly.
KWONG: It's like personalized medicine?
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.
KWONG: Jon, I'm completely obsessed with this research. I hope you keep coming back on Short Wave to share updates about it. Thank you so much.
HAMILTON: I'll be back, 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. Short Wave 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.npr.org/shortwave. Today's episode was produced by Rachel Carlson. It was edited by our showrunner, Rebecca Ramirez, and fact-checked by Jon Hamilton. The audio engineer was Kwesi Li. Beth Donovan is our senior director, and Collin 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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