Gordon: Oh, my goodness, uh, what a delight and honor to have Professor Laura Carstensen on our podcast today. Welcome.

Laura: Thank you. It’s a — it’s a honor for me to be here with you. 

Gordon: Some of our listeners have been listening to molecular and cellular biologists talking about mechanisms and model organisms and mice and flies and so on. And we really feel like  it’s time –to broaden the scope of-of the podcast and-and seriously ask where we are in terms of human aging, and that so it’s just wonderful to have you here, to-to talk  about that.

Could you just start by maybe giving us a-an outline of-of where we are in terms of human life expectancy around the world and what’s happening to aging populations?

Laura: If we zoom out for a moment, um, life expectancy throughout most of human evolution was short, and I mean really short. Uh, we don’t know for sure what it was, but the estimates of what life expectancy was as we were evolving on the African plains, uh, ranged from 18 to 20.  

Gordon: And-and this means from birth, right?So it’s not just there weren’t people that lived longer than that but from birth this was the expectancy.

Laura:   Exactly right. So that means we had, uh, an enormously high rate of infant mortality, uh, but also from examinations of anthropological finds, there were people who made it into the teen years and adolescence, death was common at all ages. Uh, and in fact there is speculation that occasionally somebody would make it all the way to, say, the fifties or even sixties. But that was really rare. And-and you know if we think about this in humans it-it threatened the survival of the species because, uh, in humans, uh, we have to not only age old enough to be able to reproduce but then hang around long enough to ensure that those offspring can get old enough to be able to reproduce. So, you know, life is touch and go for the species for mo-most of evolution.

Gordon: That’s amazing. 

Laura: It then started to kind of inch up but not until very recently, I mean as recently as the Bronze Age. If we go back 5,000 years ago life expectancy was still in the low 20s. 

Gordon:  So, what’s happening in the last, say, 50 years?  

Laura: Yeah. Well, if we go back first to 150 years ago that’s where we really started to see life expectancy go up. So in the Middle Ages it started to tick up. It got to be like the mid-30s. In the United States in 1900 life expectancy was 47, and by the end of that century life expectancy was 77. Basically we-we nearly doubled life expectancy in a single century. So after, you know, eons of, uh, very, very slow if any change in life expectancy suddenly we see this dramatic exponential increase.  

Gordon: And so if we focus down on, let’s just take the U.S.A. and focus down on individual states, and maybe even individual counties, what-what do you see there as of interest?

Laura: Yeah, well, you know, the-the story of these increases in life expectancy, and today’s variability in life expectancy, is a story about culture. Uh, the environments into which humans are born have dramatic effects on how long they live. And that’s what happened in the 20th century, we improved, uh, the safety of water, uh, we increased the food supply, agricultural technologies began to ensure, uh, a steady, uh, stream of food throughout the year, not just in the spring and the summer.  So lots changed in the 20th century, not to mention science that led us to vaccinations, inoculations against disease, so there was a lot that happened. It’s was- really I describe it as culture change. And by culture I’m referring to the crucible that holds science and technology and broad social norms, behavioral practices, that’s what I mean by “culture”.  And so that’s what led to this leap. Now you’re asking about changes today as a function of — or differences today as a function of where people live. And if you go from the county with the lowest life expectancy to the county with the highest life expectancy the difference can be close to 20 years. Again speaking to culture, it’s what are the resources we’re born into. In some ways it’s-it’s like the Petri dish, right, uh, for humans is the culture. Uh, do we have access to food, do we have safe environments where we live, are we exposed to air pollutants and toxins within our homes, these are all factors that contribute to how long we live. And today there’s tremendous disparity within the United States and how long people live.  

Gordon: Yeah, it’s it’s shocking, really, isn’t it? I mean, if we if we zoom back out again from the disparities to the bigger picture. I mean, you’ve you’ve spent your whole career thinking about quality of life and what people experiences their aging. But many of us use this word healthspan, amongst the biologists. And I wonder if you, you also use that word, and then go a little bit further to, to answer the question as to whether healthspan or quality of life is tracking with increased life expectancy or not. Is there a gap opening up?  

Laura: Yeah, well, that-that’s, um, the answer to that question is pretty sobering actually, and, uh, we are increasing health span if we take the long view. So if we go from 100 years ago, uh, we’re-we’re healthier as we get older. Um, if we look at just the last 50 years what we’re starting to see are differences in how closely healthspan tracks to life span.  Some people call this, by the way, the compression of morbidity, so the ideal would be that we stay healthy until the very end of our lives. You’re born, you have great physical health, uh, a couple days before you die, uh, you might get sick but most of your life health span, your healthy life, matches your life expectancy, the length of your life. And, um, of course compression of morbidity is really the-the goal. It’s the goal of basic geroscience, it’s the goal of, uh, societies, uh, families, communities, we want to be able to be healthy throughout our lives. What we’re seeing in the United States is a compression of morbidity if we look at the most affluent people in society.  

Gordon: I see, yeah.

Laura: But for most of the U.S. population we’re not seeing a compression of morbidity. So to me that’s good news and bad news. Uh, the good news is it’s possible because we’re seeing it now so we know that we can achieve this. The sobering part of it is, is that the vast majority of the population is not in that group of affluent, educated, financially secure individuals and we’re not seeing much compression of morbidity there. 

MUSIC BREAK

Gordon: You’re a psychologist by training and a social scientist and, um, I-I just wondered when you got into all this. What age did you kind of think to yourself that’s what I want to do for the rest of my life?

Laura: Well, I was pretty young when I got interested in aging.  Uh, in my undergraduate years I was interested in the degree to which aging, which is a biological process absolutely, but that where the degree to which that process of biology was shaped by the social world, that was really the interest I had, uh, when I first began studying aging, um.

Gordon: What was your major in?

Laura: I majored in psychology. When I first got interested in aging I assumed that I should go into medicine, uh, because those were the people who worked with older people. And you know at the time, this is the 1970s, at the time old age was often equated with illness. You could almost use them synonymously. Aging meant getting sick. Uh, and it meant that in psychology too by the way. I had a — I had a textbook when I was in graduate school that had a chapter on different psychiatric disorders. There was a chapter on phobias, a chapter on depression, a chapter on addiction, and then there was a chapter on old age. It was just called old age! So old age was considered pathological, and the thinking was, as you no doubt know, many people thought dementia was an inevitable consequence of aging too.  It was some people who got it earlier than later, but, you know, that was — that was the fate of-of living a long time. So the view was pretty negative. But when I got to-to — I-I took a course in the medical school when I was an undergraduate and I realized that the questions being asked at that time anyway in medicine were not about the interaction of the social world and the biological, uh, properties of aging. And so I began to explore different majors, different disciplines, to see, uh, which one might really address that question and eventually landed on psychology. And even today I think that’s probably true. You know psychology spans the, you know, basic physiology, biology, uh, neuroplasticity and so on all the way to, uh, well-being and how happy people are. So, uh, that’s how I came to psychology. 

Gordon: I think there’s a quote from your Kleemeier Award lecture from your father and it’s the tentative nature of knowledge that does not speak against science, it is science. And I was just curious when-when you heard that quote and what, uh, influence that had on you. 

Laura: Well, my father was a biophysicist, and he was the most influential scientist in my life, in all of my training. We had a very close relationship, so we talked a lot about basic science, not necessarily, um, differences across disciplines but what is science. And, he wrote about that and was deeply interested in it, in part because he thought a lot of people got it wrong who were in the sciences themselves!  That is a lot of sciences will say, uh, or scientists will say, well, we know the facts, we know that that’s how we’re different from, uh, religion. In religion you just believe things and-and in science, uh, we-we look for facts and we know the facts. And-and what my dad would say is there are very few facts. Uh, what science does is to provide a way to reject hypotheses and to rule out altern-alternative explanations when you’re exploring something. And-and so the more that we can rule out an explanation the closer we get to a truth, but we will never fully get to that truth. And, uh, his thinking about that, it was really philosophical thinking about science and knowledge and what is knowledge and-and it certainly affected me a great deal.

 Gordon: Yeah, and actually you’ve written about the importance of being wrong, and-and, uh, throughout life, and how as a scientist and even other people can-can really grow from that, recognizing that you-you’ve not seen the way they are.

Laura: Right. But it’s so hard. I think this is a psychological aspect of humans that, why would that be so hard? But it is hard. You know, we have — we have designed the experimental method so that we can, uh, we can really test things without them just being subjective perceptions, right? So-so but-but humans are storytellers, uh, by nature. You know we-we look at associations and we start to, uh, think about cause and effect. And it’s really hard to get people to question it, uh, psychologically. Humans, we-we want to believe that what we see is really the reality. And, uh, it’s-it’s hard — it’s hard for people to get to a point where they can be more tentative.

Gordon: You’ve talked about the need for psychological and social changes, to to happen along with this sort of biomedical approach. So they need to go hand in hand. Now we hear about the difficulties of behavioral changes in society. And so in some ways the priority is not the biology, the priority is preparing society for the potential changes that could come along. Would you agree?  

Laura:  There are individuals today who are super interested and excited about the basic biology of aging. And sometimes when I talk to them about the psychology of aging and societal changes with age, they go, “That’s not what I do, though. That’s not what I’m interested in.” I’m interested in the basic biology of aging and really living longer and healthier. And I say you need these social changes. You need to think about societal changes, individual changes, psychological changes more than ever. Imagine if tomorrow there was this advance that let us live healthier, say, 15 years longer, than we did in the past. We need to rethink our lives, how we live them. What does a life course look like? When do we get an education? What should childhood look like? So there are so many implications of, of these increases back and forth, that bear deep thinking. If people are thinking about living healthier for longer, we need to think about why. What’s that for? Oh, it’s not simply for the number. It’s so we can do something with our lives. And what would that be? 

Gordon:  So I’m sitting at the heart of the Buck Institute here in Marin County devoted to suppressing the diseases of aging and maybe even extending lifespan. And, and what comes with that is, I guess, a sense of aging as the villain. And your body of work doesn’t really say that. It actually is a very optimistic view.  

Laura: There are many myths about aging, and I sometimes think the misery myth is the most pernicious. Because if people believe that they will get increasingly unhappy as they grow older, then why should we care about staying alive and staying healthy and fit and happy, right? It turns out not only is misery not inevitable, the older people get, the happier they seem to get. And to be clear, there, it looks like it’s not so much happiness going up as it is negativity going down. So, older people experience less sadness, less anxiety, less fear than middle aged and younger people do. And no less happiness day to day. And so on balance, people are getting happier. That’s the way to unpack those findings.  

Gordon:  It’s really amazing. I mean, it is truly an eye opener for people who don’t think about this very often. And then another myth, I think, that takes us closer to the biology that we’ve been talking about in previous episodes is the idea that this is all driven by our genes and is deterministic in a certain way. Do you want to comment on that?  

Laura:  Sure. An awful lot of people in the general public continue to think that the way they will age is dictated by their genes. You know, your you, your parents, you know, give you a good hand to play or a bad hand to play. And it turns out that the more we learn about genetic influences on aging, the more we turn to environmental effects of aging, because it looks like they’re probably more, more influential than genes. That is, there are some genes that are absolutely potent. You know, if you have a Huntington’s gene, you know, then you have an increased likelihood, right, of having Huntington’s disease. But, you know, there’s no way around that. But for most things, you know, if you’re going to develop cancer, if you’re going to, get heart disease, those have genetic contributions. But lifestyles are extremely important. Now, when people try to parse out what percentage the, the, the party line is, it’s about 30% genes and 70% lifestyle environment. I think that’s even a naive way of looking at it though, because everything’s in interaction, right? It’s how they interact, how is the environment interacting with my genes? And that might be different than how the interaction, how the environment interacts with your genes. Gordon. So I mean, almost everything is an interaction.  

Gordon: Do you think there’s any hope in this view of capturing the exposome? Everything that we are exposed to through life, contributing to aging trajectories, how do we how do we even study that? And do you see some hope there?  

Laura: Oh, that’s the question for you, Gordon. You tell me. I think we’re a long way from getting there, is what I think. How about you?  How close are we to something? That’s exciting!  Gordon:  Yeah, it is exciting. And. You know, I think some, even some studies show an even bigger percentage, an environmental influence on, on life expectancy. And, and so you have to turn to expose them in some ways. Now how do you study that. Obviously there’s compartments of studies where you people are looking at environmental toxins, looking at nutrition, looking at exercise. So there’s the whole compartmentalize right now and I don’t I, I don’t have a brain that can ever bring that all together. But it is exciting to to think about.  

Laura:  Maybe it’s one of the things AI will help us. 

Gordon:  That’s right, that’s right. I mean, if we were able to capture, some sense of the exposure, all these factors that play into our life from, from, from birth to to aging, do you think that that you, as a psychologist, a social scientist, would be in a better position to make predictions about the populations that you study or to be able to understand the the observed results in those populations?

Laura:  It’s a fascinating question. There are relatively simplistic ways of looking at it. You know, how much air pollution am I exposed to, and, you know, I hear climate scientists talk about being able to predict asthma and middle age and dementia and old age as a function of how many meters you live away from a highway overpass. So that’s one example that can be, you know, measured relatively directly. You know, from a psychological perspective, it would be fabulous to know what kinds of behavioral, environmental, exposures lead to my having confidence in my decisions. Lead me to be loyal to friends, to be conscientious about my behaviors. It’s like, what? What are the factors: social, emotional, physical that create differences in individuals and how they perceive their own control over the world? That’d be really making headway.  

Gordon:   That would be amazing. And it touches on you’re very well known for your social emotional selectivity theory. And I think that’s what you’re describing here in some ways. And maybe you could just unpack that a little bit more.  

Laura: Sure. Socio-emotional selectivity theory is a theory that’s really grounded in the uniquely human ability to monitor time and especially life time, so other species can monitor time in, the hour time on a calendar. But humans through most of our lives are aware of our own mortality. And what the broader field of psychology has shown many times is that goals are always set in temporal contexts. We can’t really execute a goal or begin to pursue a goal without some time factors considered. And what socio emotional selectivity theory maintains is that goal priorities shift as a function of how much time we perceive to have left in our lives. Now, because time horizons grow shorter as we grow older, there are many predictions that my group makes about age and the kinds of goals that people pursue, but at its core, it’s really about time horizons, not about age. It’s only because those two things are correlated that time horizons and age speak to one another. And in fact, in many studies we’ve tried to remove age from the equation and just see if time horizon changes in time horizons lead people, young people, to make decisions like old people in old, to make decisions like young. So that’s a lot of the work we’ve done. But here’s the what the the real part of it is that when time horizons are long and diffuse, vast as they typically are in youth. People prioritize learning and exploration. And when time horizons are constrained as they become the older we get, people prioritize emotionally meaningful goals. And there’s a very simple way of thinking about this. It’s that when you’ve got a long time horizon in front of you, you need to collect things, people, information, knowledge, skills because they may be useful to you in the future. So we’re in a collecting mode, but when time is running out, we focus on goals that we can realize in their doing, in the moment. And those tend to be about feelings, about, meaning, about doing things we really care about. 

Gordon:   And that manifests itself in happiness in some of the things you were talking about earlier. I just turned 30 last month, oh no wait a minute, 60 last month. So, I’m waiting for that wave of happiness to come over me. 

Laura: Well, you’re still pretty young, Gordon. I mean, you know, here’s a thought I’ve had because of this potential increase in lifespan: would we see these positive changes, you know, be pushed out way into the future? And theoretically, according to my work, we wouldn’t see happiness come about in the 60s because typically people today like you in their 60s perceive the future is very long. And so, we’re we’re still we see some constraints, but we’re seeing a more at the intellectual level than the emotional level of really feeling like today, this year could be my last year, when people reach very advanced ages or, health problems, they start to say, I don’t know if I’ll see another year or you have a visit from an old friend. And, you know, at some level it might be the last time you see this friend.

Gordon:  Yes.  

Laura: Those are the kinds of changes that prime, this sense of focusing on the present, on the here and now and worrying much less about the long term future.  

Gordon: And then your studies, have you seen differences, gender differences. And what might cause those- is that the perception that women live longer than men, or is it something more ingrained? 

Laura: Interestingly, we don’t see gender differences. I think that males and females don’t have sufficiently refined expectations about life expectancy to see those differences. These are more general kinds of differences and very idiosyncratic too. So I might have a longer time horizon than my next door neighbor who’s the same age.  

MUSIC BREAK

Gordon: One selfish thing I’d like to get out of this conversation is to ask you about your views on the biology of aging that you see going on. I know you’ve thought, thought about and written about SST interventions and whether that ever crosses into the biology when you think of it, those interventions. What do you see? I mean, stress in aging and the psychosocial stress and the biology of stress have at least some communication to each other. And there’s evidence that psychosocial stress causes biological change that can accelerate aging. Is that an area that you follow at all?  

Laura: I follow it some.  I don’t have great expertise in it, but it’s fascinating, of course, to think about, we are affected, at cellular levels by psychological stress. And the mapping of that is relatively recent in psychology. Steve Cole at UCLA has done a lot of work in this where he’s actually showing how these, these external beliefs or social influences come to be manifest in our basic biology. He and other people have done similar studies where you can tell people they’re being exposed to something or tell them they’re not being exposed. And you still see this. If they think they’re being exposed, they show this biology. It’s been shown with nutrition and the consumption, consumption of foods. Like I can tell you- if I tell you that a food has a very high caloric index to it, you respond to that differently as if you do the same food. But I tell you, it’s a diet food. It has very few calories. And so these are, you know, there’s a lot of evidence that that, that our, our basic biology and our beliefs are, are working hand in hand. We, I think this is one of the most exciting areas of psychology is figuring that out- is what are those pathways and how can we change our biology by changing our psychology.  

Gordon:  So when you go to a Gerontological Society of America meeting and you know they split up with the social scientists and the clinicians and so on. And then there’s, you know, a relatively small group of biologists that they end up meeting. Do you ever go to the biology sessions and what would you like to hear there? What would you like to see biologists doing right now that would inform on on your world?  

Laura: Yeah. Oh, well, first of all, I almost exclusively go to the biology meetings instead of the psychology ones. And this is just my own, kind of cynical, I guess view of, of, conferences, as, you know, you can go here a ten minute talk on something you already know about, and you’d probably do better staying in your hotel room and reading the paper. It’s kind of nice to see in here, but, boy, when I go to the Gerontological Society meetings, it’s really exciting because there’s such a diversity in disciplines. So, you know, the unifier is we’re interested in age across this. But, you know, I so, I love to go to the biology sessions and the policy sessions, both of those because I don’t have much expertise. So I can hear what people are saying about, you know, Medicare and Social Security, or I can go hear about Geroscience and the progress being made there. It’s such an exciting time in basic science. In fact, I think that, I think it is the most important and most exciting, let me say science today. 

Gordon: That’s wonderful to hear you say that. It also sort of begs the question, I guess, when you go back to your colleagues and and even to your populations that you study, what do you think the reception is going to be of this new science? Now, let’s take the extreme. The extreme would be interventions that really push back chronic disease by five, ten, 15 years, compress morbidity, which we do see in animal models, by the way, we see this, and maybe extend lifespan by a significant margin. What’s the response going to be from your colleagues and what’s the response going to be from the kind of people you study in different age groups like the elders, the middle age, the young?  

Laura: I think if breakthroughs come where people can reliably count on health as they grow older, we will see extraordinary progress in the workplace and families and communities. Because we will be able to be confident about what our plans are. You know, the older we get, the one thing that starts to interfere with plans is you don’t quite know. There’s some question about time horizons when you’re in your 30s, people tend not to question whether five years out they’re going to be able to do something or. Not when you’re in your 60s and 70s. You say, well, five years, you know, today for me, when I say somebody says, well, do you want to you’re going to admit another graduate student? That’s a five year commitment, right? And at some point you start to go, I don’t know. You know, you start to think about it. So it’s kind of one of those early signs. So I think if we could count on being healthy at old, more advanced ages, we would work longer. We’d have different kinds of work plans. Probably more people would go back to school to retrain, to do, because the time horizons are there to be able to do something with it. And so I think it’d be phenomenal.  

Gordon: What do you think that the evidence that you would like to see would look like? I mean, we, you know, I, we can show you pictures of mice that look younger or, you know, graphs of compression or probability or so, in a mouse. And so are you looking for that, that human clinical data before you get too excited.  

Laura:  Yes, I am! So I have to, you know, I mean, when you talk about working with my colleagues, one of my closest colleagues is Tom Rando. Tom, has, you know, a stem cell, biologist, geroscientist. He and I co-founded the Center on Longevity. And so we work closely together, and we’re very good friends and colleagues, and I’ve learned so much from him. And then, of course, I have other colleagues like Eric Burdon and Tony Weiskopf and people. So I, I, I do interact with people who are working in this area from the understanding I get from them. We’re a long way from taking mouse models to being highly confident about the human models. Right. So I, I heard and you tell me if I’m wrong, about 5% of mouse models eventually transfer, as you would see in mice to humans. So there’s, you know, there’s absolutely reason to be excited about the science. If you’re counting on a particular scientific intervention, biological intervention to give humans that kind of, increase in, say, life expectancy, I, I, I’d not put a lot of money on that bet myself.  

Gordon: Your numbers are absolutely spot on, Laura. One thing, though, that gives me optimism is when you target aging itself? So if you find an intervention that actually slows aging in mice, sorry. And even simple organisms, worms and flies, the numbers are much higher translating into mice. And hopefully that speaks to possibly a higher number translated into humans, but well, only to find out.  

Laura:  It’ll be wonderful. Wonderful. Of course! And I, I, I’m, I’m hoping that happens. You know, I, I recently had a conversation with a geroscientist and, and I said, so if it turns out all this work on slowing aging ends up only, I put this in quotes for those of you who can’t see me, only curing cancer, will people be disappointed? You know, that’s kind of, that’s that’s part of why I think the science is so interesting, actually, is that whether or not we accomplish, dramatic increase in healthspan when you have this many extraordinary thinkers and scientists working on a problem of understanding what aging is, we will have breakthroughs. So, you know, I, I what I’ve said to people, and I teach a course on the business of longevity at the business school at Stanford, and we’ve had some people talk about different companies, you know, that are bringing to market some of these kinds of interventions. And I remember saying last quarter, at one point, if I were betting woman, I’m not sure I would bet on any particular company at this particular time in history to say, I’m going to give you all my money because this is going to pay off. But at the same time, I bet the family farm that something big is going to come from this effort at this time. 

Gordon: Well, I share your optimism. Delighted to hear you say the things you’re saying. I think this field is amazing. And it is becoming truly interdisciplinary across biology into the social sciences. And you’re a big part of that, Laura. So thank you. It’s been really fun to talk to you today. And thank you so much for your time.  

Laura:  Thank you. It’s just been a great pleasure for me too get to talk to you  Keep up the good work!  

Gordon: Thank you for listening. Please subscribe, share and give us a five star review in Apple, Spotify, or wherever you get your podcasts. We’re Not Getting Any Younger, Yet! is produced by Vital Mind Media. The Buck Institute’s very own Robin Snyder is the executive producer. Wellington Bowler is right next to me directing the recordings. Stella B is behind the scenes ready to debrief when we wrap. And the esteemed Sherif Ezzat weaves the show together for you. 

If you’re listening to the podcast, you’ll know that there has never been a more exciting time in the research on aging. Discoveries in the lab are moving to the clinic to help us all live better, longer. The Buck Institute depends on the support of people like you to carry on our breakthrough research. Please visit us at Buck Institute.org to learn more and to donate.