Obesity: the links with age and socioeconomic status

Christopher J. Ruhm interviewed by Romesh Vaitilingam, 12 June 2009

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<p><em>Romesh Vaitilingam interviews Christopher Ruhm for Vox</em></p>
<p><em>May 2009</em></p>
<p><em>Transcription of an VoxEU audio interview [http://www.voxeu.org/index.php?q=node/3654</em></p>
<p><strong>Romesh Vaitilingam</strong>: Welcome to Vox Talks, a series of audio interviews with leading economists from around the world. My name is Romesh Vaitilingam, and today's interview is with Christopher Ruhm, Professor of Economics at the University of North Carolina at Greensboro. We met in May 2009 at a conference hosted by the Center for Market and Public Organization in Bristol. The conference is all about the economics of dietary obesity, and I began by asking Chris to explain what his research on this topic was looking at.</p>
<p><strong>Christopher Ruhm</strong>: We're looking at a couple of things. First is how does body weight and obesity change with age, and then how is that related to socioeconomic status particularly with the notion that people who are disadvantaged or low SES are more likely to be overweight or to be obese. And how does that change as people get older. Then we try to figure out why that's going on to the extent we can.</p>
<p><strong>Romesh</strong>: Chris, tell me about the data that you've been looking at to try and analyze this issue.</p>
<p><strong>Christopher</strong>: The data are from the National Longitudinal Survey of Youth. This is a survey of originally 12,000 or so youths aged 14 to 21 in the initial year of the survey, and then they were followed. We actually observed them a total of 15 times over roughly a 20 year period. So, we're following them from late adolescence, early adulthood, through middle adulthood, so from say around 18 or 20 until in the 40s depending on the specific person.</p>
<p><strong>Romesh</strong>: So, you're looking across those range of people who are presumably a representative sample of the U.S. population, and looking at how their obesity changed over time. And I assume, we would think that they would maybe get fatter as they get older. And then how they're influenced by their backgrounds, their race, their ethnicity, their education, their socioeconomic status generally.</p>
<p><strong>Christopher</strong>: Yeah, exactly right. If you look at people in early adulthood, so say 18 to the early 20s, up through the mid 40s, yeah, they get heavier over time, so they're more likely to be obese. And then the difference by socioeconomic status increases over time. Our main measure of socioeconomic status is the education of the individual's mother, but we also look at a number of other alternative measures. This is socioeconomic status early in life. The other thing we try to do is try to understand what's going on, and is that because being disadvantaged when you're young translates into being disadvantaged when you're old, or is due to changes in income or health behaviors or those sorts of things?</p>
<p><strong>Romesh</strong>: So, what do you think are the mechanisms that go on? What is it that leads from poor, low socioeconomic status to greater tendency to be obese later in life?</p>
<p><strong>Christopher</strong>: Yeah. So, we discover there are two main linkages, and I want to be careful about saying they're linkages because we don't know what's causing what exactly. But, people who are disadvantaged when they're young get less education when they're older, and that seems to be an important avenue through which this operates. The second is the whole role of race and ethnicity. So, those are the two most important factors that we see. They'll explain maybe, depending on the age and the specific group, around half of the difference. The other half we really can't explain, and we look at things like health behaviors, family composition so you're married, how many kids do you have, that sort of thing and income later in life. And none of those seem very important once we take into account the role of education and race ethnicity.</p>
<p><strong>Romesh</strong>: What kinds of things are going on medically with these people? Is it people just not taking care of themselves? Are they eating badly, making bad decisions about the way they live their lives?</p>
<p><strong>Christopher</strong>: Well, that's a great question, and we really don't know. When we look at this, we're interested in the broader relationship between socioeconomic status and health. And it's true in our study, but in other studies as well, when we find there's an important effective education or an important linkage with race and ethnicity, it's very hard to know why. Now, we try to look at health behaviors. We don't see those as being a predominant measure, but the behaviors we have are quite limited. And so, for example, we don't know anything about diet. So, my suspicion is a lot of what's going on is it's operating through differences in diet, but we don't have the measures for that in this study. So, we can't identify it precisely.</p>
<p><strong>Romesh</strong>: Well, what does economics bring to thinking about this issue? Because you think of obesity as being very much a health issue that might be looked at by researchers in medicine and health. What does economics particularly bring?</p>
<p><strong>Christopher</strong>: Economics, I think, brings two or three different things. The first is we look at obesity and health measures partly as the result of a set of choices that people make. So, they make choices about what to eat, about how much exercise to get. That's a bit different than the standard approach to health, and so I think that can be useful. The second thing we bring is a lot more methodological sophistication in doing the kinds of statistical analyses that we do. So, that's something that economists are just really good at.</p>
<p>A third is in thinking about what socioeconomic status means. Often these terms are used, but they're not made precise, and so we certainly try to be quite precise. Now, we're not saying we have the correct definition, but we try to be as precise as we can in understanding what exactly we mean by that.</p>
<p><strong>Romesh</strong>: Do you feel that this body of research is in a position yet where it can make really serious policy recommendations?</p>
<p><strong>Christopher</strong>: I would say no, not yet. The problem again is we know these linkages with things like education, race and ethnicity, but until we get inside those black boxes, it's very difficult. For example, there's something about education that seems to matter quite a lot. If it's specific health behaviors, well, maybe there are other things we could do to try to improve those health behaviors. But, if it's something else entirely... For example, this isn't for obesity but management of diabetes, which often results from obesity, we know that more educated people tend to follow complicated medical regimes better. And so without knowing those underlying mechanisms, it's a little hard to say, I think, at this point.</p>
<p><strong>Romesh</strong>: Focusing on this education issue, is it very much about what we traditionally think of as education as being what kids learn in their young years, their teenage years, as opposed to going to people later in life and saying, &quot;Look you guys, it's clearly shown now that this kind of diet will lead to obesity.&quot;</p>
<p><strong>Christopher</strong>: Yeah. That's a great question, and I wish we knew the answer. I'm fairly convinced it's not due to the specific material they learn but is the idea that you learn how to learn. So, you can acquire new information more easily, and that's information related to health among other things. That could be part of it. Is it your peer group? So, you're in a peer group that's informed, that's inquisitive about these kinds of things. Is that what's going on, or is it something else? It may be that education leads you to have a lower discount rate, that is, to be willing to lose more at the present time to get more in the future. I suspect that the educational process helps you learn to defer gratification, and those kinds of things lead to better health later on. But again, to some degree those are guesses.</p>
<p><strong>Romesh</strong>: And presumably, there are similar things going on in looking at issues like smoking.</p>
<p><strong>Christopher</strong>: Yes.</p>
<p><strong>Romesh</strong>: Or well, people taking drugs or alcohol, this kind of stuff?</p>
<p><strong>Christopher</strong>: Absolutely. Yes. So, if you looked at smoking, you see a very big educational gradient. It's not information in the way we typically think of it. I mean, most people now, whether they're educated or not, understand that there are health risks to smoking. So, it's got to be something a little more complicated and subtle than that. And that's where I think a lot of the interesting future research will lie to figure those things out.</p>
<p><strong>Romesh</strong>: Well, talking about future research, where do you see your research program going on obesity and then this links with age and socioeconomic status?</p>
<p><strong>Christopher</strong>: What I'm looking at right now with regards to obesity is the whole role of how do decisions come into play? We were mentioning differences between economists and non economists. Economists do think about choices, but then we often think people are making rational decisions given the sets of constraints that are available. But, I think with something like obesity, it's more complicated, and clearly there are a lot of people who make what they consider to be mistakes. And so trying to understand that... And that could actually have some potentially large policy implications, but my work on that is preliminary at this point.</p>
<p><strong>Romesh</strong>: OK. Well, come back and talk about it next time. Chris Ruhm, thanks very much.</p>
<p><strong>Christopher</strong>: Thank you</p>

Topics:  Health economics

Tags:  obesity, socioconomic status

"Age, Socioeconomic Status and Obesity Growth", (with Charles L. Baum), September 2008, revised and resubmitted at the request of the Journal of Health Economics.

Professor of Public Policy & Economics, University of Virginia


CEPR Policy Research