Zip Codes Are More than a Number: Study Finds Link between Neighborhoods and Memory-related Brain Structures

Transcript

Intro: I'm Dr. Nathaniel Chin, and you're listening to Dementia Matters, a podcast about Alzheimer's disease. Dementia Matters is a production of the Wisconsin Alzheimer's Disease Research Center. Our goal is to educate listeners on the latest news on Alzheimer's disease research and caregiver strategies. Thanks for joining us.

Dr. Nathaniel Chin: Hi, this is Dr. Nathaniel Chin. If you are a regular Dementia Matters listener, you know that since April our episodes have focused on the very important topic of caregiving during a pandemic. The COVID-19 special series has ended, but I want to remind you that the pandemic has not. Between regular episodes about Alzheimer's disease research and prevention education, I will offer special topics and bonus episodes pertaining to the pandemic when updates feel necessary. As always, please email us at dementiamatters@medicine.wisc.edu with your questions, topics, suggestions, and comments. Today's episode was recorded back in February, since then our guest, Jack Hunt, hit an important career milestone in his medical training. In April, he defended his thesis to earn his PhD in cellular and molecular biology. This summer, Dr. Hunt will return to medical school to finish his MD training and will later go on to a residency program in psychiatry as a research assistant. At the Wisconsin Alzheimer's Disease Research Center, Dr. Hunt studied the links between neighborhoods and brain structure and aging. He was lead author on a paper that was published in JAMA Neurology that showed that disadvantage in our neighborhoods is linked to brain structures involved in memory function. I hope you enjoy this episode. 

Jack, Welcome to Dementia Matters.

Dr. Jack Hunt: Thank you so much for having me.

Chin: Now your paper, titled Association of Neighborhood Level Disadvantage with Cerebral and Hippocampal Volume, examined correlations between where people live and trends in their brains. Before you talk to us about the results, tell us what you were looking at specifically and why this is important in Alzheimer's disease research.

Hunt: Sure. So in this study, we were really interested in looking at how the context that we live, in is related to our brain structures as we age. In particular, we were looking at how your neighborhood social and economic environment relates to your brain structure using neuroimaging; both kind of globally, and then specifically in areas of the brain that are involved in learning and memory that are affected by things like Alzheimer's disease. So the ultimate goal is really to try to identify new risk markers and risk factors for dementia. Knowing some of these risk factors will really help us to be able to come up with new strategies for fighting dementia and preventing it hopefully.

Chin: Now you used the word "context of the neighborhood", Can you explain that? What does that mean?

Hunt: Yeah. So we can think of a neighborhood as both the people, and also kind of the physical environment around where you live. The context really is about several different things. There's the physical context. So things like, are there streetlights that are functioning? Are there roads? Are there grocery stores? And there's things like the social context. Are there people around that are providing social support? Are there a lot of abandoned houses and buildings, so you're not having that same level of connectedness? And there's also the economic context, are there good paying jobs available? Things like that.

Chin: So there's a lot more to it than just your zip code.

Hunt: Exactly. Certainly.

Chin: What did your research uncover?

Hunt: Our main findings were that participants from very highly disadvantaged neighborhoods actually had smaller hippocampal volumes, so about 4% lower than participants from the more advantaged neighborhoods. This was equivalent to about four to seven extra years of brain aging. We know that as we age, our brains will shrink a little bit just as kind of the normal course of aging. But the amount of difference in the brain volumes was equal to about four to seven years of aging.

Chin: So accelerated brain aging? 

Hunt: Well, this was just a snapshot of people's brains. This was just one point in time. So from this study, we can't say that it was necessarily accelerated, we just know that there was a difference.

Chin: And so what do you mean by most disadvantaged? 

Hunt: Yeah. So to kind of measure disadvantage in this study we used what's known as the area deprivation index. This is basically a composite, so it measures several aspects of a neighborhood, including the average income in that area, housing conditions, average educational level, that kind of thing. And then we take that area deprivation index and we compare it across either the United States or across all of the neighborhoods within a state, which is what we did in this study.

Chin: Who were the people specifically that you studied?

Hunt: This study was composed of participants from two studies; the Wisconsin Registry for Alzheimer's Prevention and the Wisconsin Alzheimer's Disease Research Center Clinical Cohort. Everyone in this study was actually cognitively unimpaired, so they didn't have any signs of dementia or cognitive impairment. 

Chin: And you refer to that hippocampal area of the brain in your results. Can you explain to us why you looked at this area and what actually is this area? 

Hunt: Sure. So the hippocampus is a part of your brain that is very much involved in learning and memory processes. We also know that it starts to shrink early in the Alzheimer's disease process. So we're particularly interested in this area of the brain because we know that it's really important for memory and then loss of memory in conditions like Alzheimer's disease.

Chin: And so when you think about this 4% reduced hippocampal volume, what does that mean for our audience members listening?

Hunt: Yeah, that's a really good question. One of the followup questions to this study was does this change and hippocampal volume actually translate to cognitive functioning? So that was one of our follow-up questions that we didn't look at in this study. But, we can think of it as an indication that people might be at a little bit higher risk. If their hippocampus are smaller to begin with, this might mean that it takes less to kind of push them over the edge to start losing some of their memory processes.

Chin: And you're also in essence, looking at bigger variables; neighborhood variables, policy related variables that could be affecting our thinking. And so people could look at that and say, well, I'm going to make adjustments.

Hunt: Oh yeah, absolutely. Yeah. That you know, it was one of the exciting things about this study, I think is that it really ties together a lot of different levels of thinking about our health policies, our economic systems, and then down to our biology and what might put us at risk for dementia. So I think it provides some interesting opportunities to start to think about those questions.

Chin: Now, in addition to that area deprivation index that you just explained, you also looked at cardiovascular disease factors, and I think that's an important thing in your study. Can you explain to our audience why you looked at those and which specific factors you included?

Hunt: Sure. So we wanted to look at cardiovascular factors because we know that these factors are also related to the neighborhoods where we live. So there's been previous research showing that high levels of neighborhood disadvantage are also associated with cardiovascular risk factors. And we thought that maybe some of these risk factors could also be at play in determining a person's brain structure. So it's kind of interesting to think about links between the neighborhood cardiovascular risk and neurodegeneration or loss of loss of brain structure.

Chin: You also looked at, when thinking about cardiovascular risk, things like smoking and high blood pressure. And in essence controlled for that, saying that your results meant that despite those things, it really wasn't due to that, it was due to the neighborhood.

Hunt: Right. We both thought about controlling for those factors, but then we also thought of it in terms of looking to see if those factors were kind of along the same pathway. Can we draw a line between neighborhoods’ cardiovascular risk factors into the brain? You can think about some ways that those things might be related. So things like access to grocery stores and healthy food options, access to the ability to get exercise, which we know is also related to our brain structure. There's a lot of overlap there.

Chin: And again, with this area deprivation index, can people in the community type in their zip code somewhere and see what their score would be?

Hunt: Yeah. Actually the area deprivation index through a research team at University of Wisconsin led by Dr. Amy Kind, has made the area deprivation index available publicly. It's called the Neighborhood Atlas. And you can look it up online and see it, the level of relative disadvantage in a certain area.

Chin: And we're going to have that link on our website for those that are listening so that you can click and look at yours. I think one of the important things to note though, is that it is a full spectrum when we talk about advantage and disadvantage, and I believe there's up to 10 different options or levels of disadvantage. Would you say that Wisconsin has all 10 within our state alone?

Hunt: Yeah, absolutely. We really have a full range of levels of disadvantage. If you look compared to the entire United States, Wisconsin tends to be a little bit more advantaged just overall, but we still do have a range within the state. And it's kind of interesting to look at both more rural areas and more urban areas. Because we also have a range in both rural and urban areas. It's not confined to one versus the other.

Chin: And your study examined research participants in their current neighborhoods. So not necessarily where they grew up or live between their childhood and adulthood. So is historical and neighborhood data available for different periods of time throughout their time in the United States?

Hunt: Yeah, I think that's a really interesting question. And one that Dr. Kind's team is actively working on. For this study, it was just looking at their current address. So these were middle aged participants. The average age was about 64. And I think it will be really interesting to go back and look historically to see if neighborhood disadvantage at different times in your life might also impact your brain health.

Chin: When we speak of a person's life course and the things that happen from birth to death and how that affects your brain, it seems like you opened a door to an interesting research question.

Hunt: I hope so. I hope that researchers can take this study and build on it and start to look at some of those historical factors. We know that health and dementia risk doesn't just happen in older age, it really happens throughout the entire life. So it will be important to look at that too.

Chin: Now, one of the key conclusions you report in your paper is that there is an association between brain size during aging and the community socioeconomic level. Now this is different from an individual's personal socioeconomic status. So why do you think this is important?

Hunt: Yeah, it's a really important distinction and really important to think about. So in this study we controlled for an individual's educational level, which is a really kind of good indicator of their personal socioeconomic status. And we found that both the neighborhood level factor and the individual level education separately were associated with brain structure. So I think it's important to start to tease apart some of these differences between levels of factors, so that we can really think about what would be potentially the most effective intervention strategies or prevention strategies. Something that works at the neighborhood level and individual level, they might have really different approaches.

Chin: And you did mention education level because that was a possible mechanism for this relationship between the neighborhood and brain size, but you found something interesting. Can you explain that?

Hunt: Sure. So we found that even controlling for an individual's educational level, that neighborhood disadvantaged still was associated with brain structure with hippocampal volume and global brain volume.

Chin: So there's something more than just the education level. Right?

Hunt: Exactly.

Chin: And the same can be said about those cardiovascular diseases that we talked about.

Hunt: Right. Exactly.

Chin: So while these are important, especially at the personal level, there is something beyond that when we look at a neighborhood's health.

Hunt: Yeah, exactly.

Chin: So this is a really tough question, and I know you won't have an exact answer, but I want you to speculate for us. What do you think are the possible reasons for this relationship between where you live and the size of your brain?

Hunt: Yeah, I think the heart of this research is really trying to understand this pathway between the neighborhood and your brain. I mean, it's kind of a long distance between our neighborhoods and the cells in our heads. But I think there's a lot of interesting possibilities. So ones that we've already looked at were things like cardiovascular risk factors. So things in the neighborhood that could affect these again, would be things like access to food, access to recreational or exercise opportunities. Other possibilities that we are interested in looking at in the future are things like exposure to chronic stress. So we know that unfortunately the socioeconomic advantage of an area also impacts the crime rate. So if people are exposed to what they feel are more dangerous living environments, they might be exposed to chronic stress, which we know also affects the hippocampus, those parts of the brain involved with memory. So those are some possibilities. But there's a lot of other interesting things to look at environmental toxins, all sorts of things.

Chin: I'm glad you just mentioned that because I was going to ask if there is this opportunity to overlay maps. You have this area deprivation index, and then you have state and federal maps about environmental toxins, maybe seeing if there's a possible relationship?

Hunt: Yeah. I think this'll be a really interesting thing to follow up on. There's a lot of publicly available data. I'm using mapping technology to look at things like air quality, water quality, even looking at how many grocery stores are in a given area, that kind of thing. And there's a lot of really cool opportunities to combine that with something like the area deprivation index to both help researchers to understand these processes, but also to help policy makers help community organizers. There are all sorts of people to tackle this complex problem.

Chin: So then let’s rewind from these future projects to now, what can people out in the community do with this information?

Hunt: Yeah, that's a really good question. I think that one thing that we're hoping is that this study can start to raise awareness. So clinicians, family members and community leaders can start to consider this when they're thinking about older people in their communities. They might actually be at a little higher risk for developing dementia down the road or cognitive changes. So just to be able to pay closer attention and keep an eye on these individuals and try to figure out ways to help them.

Chin: And what are your next steps after this publication?

Hunt: One of the kind of immediate next steps is to do a follow up study. So in this first study, we looked at a snapshot of people's brains, looked at structure at a single time and searched for a difference based on neighborhood disadvantage. But what we really need to know is if neighborhood disadvantage is a risk marker of neurodegeneration, or loss of brain structure as we age. So that's part of the follow up study that I'm currently working on to see if we actually lose brain structure in those memory related areas as a result of neighborhood disadvantage. So to see if there's an association between loss of brain structure in those memory related areas and neighborhood disadvantage and then also to see if there are cognitive changes that go along with those structural changes. So using cognitive testing to see if people actually are declining in their cognitive function associated with the neighborhood disadvantage as well.

Chin: I'm going to end this interview by asking you a question. I ask a lot of my guests about things we cannot control. For instance, not everyone can control where they live, but we can control what we do during the day. And I want to know from you, as someone who researches both macro looking at neighborhoods, but also looks at the brain, what is something that you do to protect your brain and age in the best way possible?

Hunt: Wow, that's a great question. I think probably the thing that I try to do to help my brain age, is to eat healthily. I try to cook vegetables, whole grains, all those kinds or things, as much as possible. I think about that not only for both thinking and aging, but just for how I feel on a day to day basis; I usually feel a lot better when I'm eating healthfully. So that's what I try to do with all that.

Chin: Thank you again, Jack, for being on Dementia Matters.

Hunt: Thank you.

Outro: Please subscribe to Dementia Matters on Apple Podcasts, Spotify, Podbean, or wherever you get your podcasts. And rate us on your favorite podcasts app -- it helps other people find our show and lets us know how we're doing. Dementia Matters is brought to you by the Wisconsin Alzheimer's Disease Research Center. The Wisconsin Alzheimer's Disease Research Center combines academic, clinical, and research expertise from the University of Wisconsin School of Medicine and Public Health, and the Geriatric Research Education and Clinical Center of the William S. Middleton Memorial Veterans Hospital in Madison, Wisconsin. It receives funding from private, university, state, and national sources, including a grant from the National Institutes of Health for Alzheimer's Disease Centers. This episode was produced by Rebecca Wasieleski and edited by Bashir Aden. Our musical jingle is "Cases to Rest" by Blue Dot Sessions. Check out our website at adrc.wisc.edu. You can also follow us on Twitter and Facebook. If you have any questions or comments, email us at dementiamatters@medicine.wisc.edu. Thanks for listening.

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Show Notes

"Association of Neighborhood-Level Disadvantage with Cerebral and Hippocampal Volume" was published in JAMA Neurology online on January 6, 2020. 

Read a summary of Hunt's publication.

Hunt and his co-authors defined the socioeconomic status of neighborhoods using the Neighborhood Atlas tool.