Chapter 1: What is the main topic discussed in this episode?
Smart, sharp, and slightly unhinged. Late night's fresh perspective. The Last Show with David Cooper. Inequality may not just live in your bank account, but also leave a fingerprint in your brain. What do I mean? Well, there's a study that suggests your social and economic status determines how your brain ages and how it starts to break down.
Let's discuss all this with someone who's done research in this area. He's a research fellow in genetic epidemiology at the Bristol Medical School in the UK, and his name is Dr. David Hill. David, welcome to the show. Thank you, David. Tell me a bit about yourself. Your research is so interesting.
Chapter 2: What is the link between socioeconomic status and brain structure?
Before we jump in, though. Yes, my work is looking at socioeconomic status and how it may have causal effects on certain health outcomes, such as the aging of the brain. And in this piece of work, what we've done is we've used genetic data to try and understand modifiable, potentially modifiable environmental exposures.
So what we had to do was to try and get a very good measure of socioeconomic status. So we took differences in income, differences in educational attainment, differences in individuals' occupation, and differences in the social deprivation in the area in which they lived. And we performed something that's called a genome-wide association study.
So what this does is look for individual differences in genetic variation that co-vary with these differences in these four socioeconomic status measures. And the reason we wanted to get a genetic measure of socioeconomic status is so that we could perform a technique called Mendelian randomization. It sounds a bit like a sci-fi concept. Do you want to define that a little bit for me?
Of course, of course. So Mendelian randomization is the idea of making a causal, is to be able to make a causal statement between two things. In this case, it's socioeconomic status and aging of the brain. So in science, if you want to establish a causal relationship, you do something called a randomized control trial.
You get two groups of participants, equal in every way, and you give one of them the treatment of the fact, be it a certain kind of surgery, an exercise program, a drug. And then because the groups are matched in every way except for this treatment that you want to assess the impact of, the only difference is that treatment.
And so you can say, because there's no differences, it must be the treatment that had this effect. Now, with socioeconomic status or education, it's not possible to randomly allocate education to someone, nor is it possible to randomly allocate income to people or their occupation. But with Mendelian randomization, what you do is you take advantage of genetic variation within population.
You don't select your genotype. So if you have a genetic variant linked to, let's say, differences in income, you can then treat these genetic variants as randomly allocated in the participants in your group. So in this way, you've got a randomized control trial as a product of natural genetic inheritance. Got it. Okay. Big picture.
Are we saying that the paycheck of our parents, where we grow up, can shape how our brain develops? Is that the basic premise here? What we seem to have found is that these differences in socioeconomic status have a causal effect on something called white matter hyperintensities. Now, what these are is very, very small lesions, sort of lesions in the brain.
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Chapter 3: How does genetic data help in understanding socioeconomic effects on health?
We don't really have them when we're children and young adults. But as we age, we typically accumulate more and more across our lifespan. And these are predictive of cognitive decline and dementia in older age. So individuals by the age of 40, if you have more of these white matter hyperintensities, you're more likely to develop dementia in older age.
Is the idea that the stress of having not as much money or growing up with less socioeconomic status causes these? I'm kind of missing the link here. How do these white matter hyperintensities develop in that environment? Well, at the moment, what we wanted to do is to establish if there is any causal link between these traits. We had a number of different brain aging phenotypes.
And by phenotypes, I just simply mean measures of the brain. So we had the white matter opportunities that I mentioned, total brain volume, different volumetric measures for different sections of the brain. But nothing seemed to be... a product or appears to be a product of differences in socio-economic status, no causal relationship. There was a correlation, but not evidence of causality.
So we don't know exactly which individual aspect of the environment is the causal element here, only that we took our differences in education, income, occupation, and social deprivation, and we found an effect of all four of these.
But beyond this, what we did is we looked to see if a single underlying dimension, genetic dimension, could explain the variation across these four socioeconomic status traits. Now, what I mean by this is that if you perform a genetic study on something like educational attainment, you're not capturing the DNA consequences of getting a degree or not getting a degree.
but rather you're catching other traits that lead to differences in how you get the degree. So your measure of education might be capturing your level of intelligence, your come to ability, aspects of your personality, other aspects of yourself, how hard you work, how prone you are to disease.
But we found there's this underlying genetic dimension across all four of these measures of socioeconomic status. And this underlying genetic dimension is what seemed to have the causal effect on brain health as measured by white matter hyperintensities in older age. I mean, you asked the question exactly how that link works. Yeah.
Could it be like stress, access to health care, access to healthier food? Like there's many such reasons, but I'm curious if you have any, I don't know, speculation as to which one it is. Or maybe it's the combination of them all.
Well, by finding this underlying genetic dimension, what it indicates is that it wouldn't matter so much which of these aspects of socioeconomic status we sought to improve because we'd still be seeing the good effect on your brain health as gauged by white matter hyperintensities.
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Chapter 4: What is Mendelian randomization and how is it applied in this research?
It is an interesting, fascinating link, and I appreciate you coming on the show. Thank you so much for having me. Dr. David Hill is a research fellow in genetic epidemiology at the Bristol Medical School. TV's hottest show. It's off. Be safe. Keeps getting hotter. Will you help? Happy to. Fire Country. Only Fridays at 9 Eastern on Global. Stream on Stack TV.