The effects of climate change are evident around the globe. These impacts are affecting ecosystems and communities worldwide, with many implications for human health. In this episode of Dialogues, I talk with Dr. Amir Sapkota, professor at the University of Maryland, and an expert on the relationship between human health and climate change. From investigating the relationships between frequency of extreme events, changes in plant phenology and increased risk of respiratory diseases, Dr. Sapkota is developing public health strategies to combat the effects of a changing climate.
Dr. Maddux: Tell us just a little bit about your sense of how climate change can actually affect human health and just give us a little framing of that as we get into our discussion.
Dr. Sapkota: So I think to start the discussion I would like to first start by talking about the climate-related exposure, right, so what does it mean to be exposed to climate change? So one of the things that we look at is extreme weather events such as heat waves, extreme precipitation, droughts, wildfires and so on and so forth. If we look at the historical data, well, heat waves has always been around, but what is different is that the frequency, intensity and duration of such extreme heat events are changing in that the heat waves are becoming more frequent and when they do happen they tend to be a lot nastier and they tend to last longer. And we have excellent empirical data showing this. And as we look into the future decades, what the climatologists tell us is that this trend will continue into the future decades in response to anthropogenic climate change. So the question then becomes how does such extreme event impact human health and there's lots and lots and lots of data around us documenting this. Heat wave, for example, can lead to heat stroke, increase risk of mortality, hospitalization for a number of other health, you know, outcomes. So this is some of the example of direct impact of climate change on human health. Then of course there are other indirect impacts that are a little bit less discussed that we can get into.
DR. MADDUX: So thinking about acute and chronic impacts of this, do you think it's frequency, intensity or duration of these extreme weather events that impact folks either in the long-term or in sort of the short-term?
Dr. Sapkota: I think all those three elements are very important. Of course, you know, for it to, you know, have an impact and you need that extreme event, heat event to take place, right. So the frequency is absolutely critical. But when they do happen, you know, like how, you know, what's the intensity of that exposure and how long do they last. I think they are all very critical. There's been some study that, you know, have shown heat waves that last longer tend to be a lot more nastier in terms of, you know, how it impacts hospitalization risk or risk of mortality and so forth.
DR. MADDUX: You and I were coauthors on a paper recently related to the impact of heat events in patients with advanced kidney disease. And I'm just curious what other disciplines of medicine and other health care activities we think predominantly around respiratory-type illnesses and things like that, but what are some of the other things that you've studied with regard to health impact for individuals?
Dr. Sapkota: So one of the examples that I would like to give you is respiratory illnesses, you know, including asthma and asthma exacerbation. So we have shown and many other studies that are out there have shown yes, this extreme heat event can increase risk of asthma hospitalization because heat is, you know, a precursor to a lot of other pollution including ozone. So when the heat increases, the ozone concentration in the environment increases as well. But the other example that I would like to give you sort of like gets at it from more indirect pathways so to speak. So when the wintertime temperature and the springtime temperature, for example, are higher, the timing of spring onset, this is when your trees start to bloom, when your tulips come out, you know, they shift, right. So when the springtime temperature is warmer, trees start to bloom earlier. Now why is that important? Because tree blooming in North America signifies start of pollen season. So if the trees are blooming earlier, that means the pollen season is starting earlier so the duration of exposure to pollen is longer. So if you happen to be somebody living with asthma or other allergic condition, that's, you know, not a good sign, right. So that's one thing. And the other side of that spectrum is in fact when the, you know, temperature is very erratic and the spring gets pushed back, so rather than, you know, spring starting let's say in, you know, end of February, early March, it's pushed back to the end of March. So what happens in those situations is that, you know, the trees don't bloom, they don't bloom and all of a sudden all different species of trees will gangbuster simultaneously. So the pollen season actually may be shorter but the propensity of exposure is much higher. The pollen concentration in the environment can be very higher because every different species is blooming simultaneously. So that also is a risk factor for asthma hospitalization. So it comes at you from both directions. Similar to if you look at temperature, right, very hot temperature kills you; very cold temperature kills you as well. There is a sweet spot in somewhere in between that we like. It's the same thing it turns up, it's the same thing with the timing of spring onset too is that when the spring starts very early we are exposed to longer duration of pollen. When the spring starts very late, you know, then we may be exposed to smaller, you know, shorter duration but the exposure level tends to go up so that also increases your risk of asthma hospitalization. So this is an example of what I earlier mentioned to you as an indirect pathway in that your climate changes actually impact the timing of spring onset. Climate change and climate variability, I should say. So it's impacting the timing of spring onset in that changes on that timing of spring onset is then increasing risk of asthma hospitalization among individuals who live with asthma.
DR. MADDUX: How plastic and flexible are human responses to, for example, temperature changes that they have chronically over time? Do we have a lot of plasticity in our response to accommodate climate change or is there a fairly narrow window?
Dr. Sapkota: I think one thing that distinguishes our species is we are incredibly resilient. So yes, you know, we have that capacity to adapt, but there is certainly a limit to that, right. So the fact that, you know, humans are living in the most coldest place and in the desert environment is a testament to how resilient we are and how we can adapt to it. So I think we are definitely very capable of adapting to that. But it's the changes, you know, that oftentimes gets us, right. So but we, what we also need to think about that is yes, we are, you know, very capable of adapting but there are amongst us very vulnerable population. You know, people that are not able to handle those, you know, exposures. So I want to say this in the context of where the world stands as of today, you know, if you look at, you know, we have made a tremendous stride in terms of increasing life expectancy, whereas in this country, you know, like 70, 80 years, you know, 70 years ago, life expectancy was in the fifties and now people live routinely in their eighties, nineties and even hundreds. But that increases in life expectancy is all not healthy life, right. So a lot of people are living with what we call these chronic conditions, right. So how do these added stress, you know, and this exposure impact these vulnerable people that are already living with, you know, diabetes; that are already living with congestive heart failures; or COPDs or a host of other, you know, ailments. So that's, you know, those are the population we are, you know, very concerned about because they do not have the capacity that normal people do in terms of, you know, adapting to those changing conditions.
DR. MADDUX: So let's shift gears for just a minute and talk for a moment about two things. First I'd like you to just for our audience distinguish climate and climate change from weather and what are the distinctions there; and then secondarily, let's talk a little bit about what's driving climate change in general.
Dr. Sapkota: Weather is basically what you get, right, to look outside your window. Today right here in Maryland it's a beautiful, you know, mild fall day, right. That's very different from Florida. That's very different from California. That's very different from Boston, right. So weather is the current condition given the location, right. Whereas climate represents an aggregate pattern of weather. So when somebody asks you how's the weather like in Boston, they're not really asking you how the weather is today, you know, they're asking in general how the weather is like in Boston. In the fall, it's cool. In the summertime, it's hot and humid. How's the weather in Florida? It tends to be very, you know, always hot. They're not talking about today or, you know, a certain location. So weather tends to describe the aggregate-- I mean, climate tends to describe the aggregate pattern of weather. And then there is climate variability, right. And so just to take a step back, so temperature is just one aspect of that. We could be talking about let's say the area covered with snow. Or you know, frozen lakes. So if you happen to live in Minnesota, for example, you know, a lake in Minnesota in the middle of winter gets frozen, right, and you go ice fishing, for example. So every year it's your family tradition to go ice fishing on Christmas day and all of a sudden one year you cannot go ice fishing because the lake is not frozen. Does that mean it's a climate change? Absolutely not. But if year after year after year, like in your, you know, family Christmas holiday all of a sudden you cannot go ice fishing because that lake is not frozen, whereas before when you were growing up it was always frozen and that was your family tradition but you can't do that anymore because year after year it's been, you know, unfrozen. So now all of a sudden there is a new paradigm that's emerging and that's' different from the old paradigm and that's a climate change because it's different from the prior paradigm.
DR. MADDUX: I think those independent definitions are actually important because in the public sphere we frequently hear people that might deny issues of climate change or what the condition is in the long-term of our environment. And what they're really trying to recognize is that the weather will go up and down, the temperatures will go up and down, the rain will come and go, the winds will change. But this fundamental change over time really is a different measure of how we're looking at both the climate impact and of course for us, as physicians and health care workers, trying to look at how does that impact our societies and how we work. What are the causes of this long-term climate change, not a weather event, but the long-term climate change that we're seeing, what is driving it predominantly in today's world and what are the things that you see that would begin to address some of those issues?
Dr. Sapkota: One of the major drivers are the greenhouse gas emissions. You know, these are energy trapping gases that, you know, drive up the temperature in our planet. But in terms of talking about, you know, I'm going back to your question about, you know, like what can be done and what, you know, obviously all of us have a role to play in it, right. So a lot of times people tend to think that my small contribution is not going to make any difference. And I say to that, because it's really it's every single drop of water that makes the ocean. So yes, you know, if everybody were to say that then we're not going anywhere; but if everybody is committed to making some contribution, those collectively make a difference and I think that's what's being lost in this discussion is that everybody has a role to play.
DR. MADDUX: To what degree does the impact of climate change on the health of people sort of uncover the ethnic diversity and the social diversity of impact of this? Can you speak to that for a moment?
Dr. Sapkota: If we are to look at chronic kidney illnesses, particularly end stage renal diseases, right, so the lifetime risk of developing end stage renal disease, for example, is almost 8 percent in African-Americans as opposed to if you look at the Caucasian, that's like 2 percent. Right, so huge difference exists, you know, racial and ethnic disparities exist in terms of the prevalence of those diseases. There's also differences in terms of access to care, right, then differences in terms of, you know, other preexisting conditions such as diabetes, obesity, you know, things of that sort that are also related to, you know, these chronic kidney diseases, is obviously. So when you have then this external exposure, let's say extreme heat event, you know, that takes place, then obviously it's going to have a disproportionate impact on those, you know, populations because really having a better understanding of these underlying differences. I think that's really, really critical moving forward because I'm sure we'll talk a little bit about, you know, how we adapt to this too. And, you know, in terms of that sort of, like, in-depth understanding of the underlying vulnerability both in terms of racial-ethnic differences but also geographic vulnerability is very, very critical because then only we will be able to target, you know, those populations with intervention.
DR. MADDUX: How do you think we should be measuring the health impact in these populations generally and especially for us and our kidney disease population, are there any metrics or particular methods we should be looking at that we don't do today routinely?
Dr. Sapkota: Let's say for example somebody is prescribed to a low potassium dialysate because they are hyperkalemic, right. But this person then comes to undergo dialysis, for example, and it happens to be, you know, right after a major heat wave. So that in this individual, he or she has undergone extra renal loss of potassium because of through perspiration. And so then they will come and undergo dialysis with the low potassium dialysate. I think that may increase their risk of, you know, cardiac arrest further. So I think, you know, in response to your question about what can be done, how should we be measuring about this is it's not only, you know, measuring the risk of hospitalization or mortality but also what are the, like, subtle drivers that may be, you know, contributing to these increases in risk, sort of like what we call the different modifiers, right. And I mention this because these are, like, in terms of moving forward, there is pretty, you know, straightforward solutions to that, right. So if we know in fact, yes, you know, this patient undergoes, you know, is experiencing a loss of potassium, then the solution is pretty straightforward. Maybe like rather than measuring the baseline potassium once a month, you could conceivably, particularly during, you know, hot summer months, you know, measure it right before the dialysis and adjust the dialysate accordingly, right. So I think those are the subtle things that, you know, can be modified. I mean, so this is what I mean by informing the location-specific treatment protocol. You know, I think that's where there are a lot of action is.
DR. MADDUX: So I think that's a very timely comment that you make because we have regular discussions these days around how we move our diagnostics capabilities within our treatment ecosystem to something that's much closer to real time. Because in many cases there are a number of analytes that change with a frequency such that a monthly lab has much less meaning that would allow you to tailor a prescription for today's condition and not the condition from two weeks ago or a month ago.
Dr. Sapkota: Yeah.
DR. MADDUX: And so I think that your example of the impact that the environment and whether it's a weather event or it's a climate change-related activity, what are the things that in fact we would reassign how we prescribe therapy is actually quite telling and I think very important.
DR. MADDUX: I think that's an excellent point. And I think this is also the sort of, like, sneak peak of ways that, you know, at things that are to come into the future, right. So I think we are going to see more and more of this kind of scenario. So the question then becomes sort of like how do these different risk factors interact with each other and do they, you know, is the joint effect of those risk factors much worse than individuals. Climate change is here and it's not going anywhere in the near future, right. So what we know is such extreme events are becoming more frequent and they will continue into the foreseeable future because of the changes that are already ongoing. So the future of medicine is really how do we anticipate these threats and adapt to them in advance, right. You know, so you can have a preventive measure in place rather than reacting to the threats after the fact. I think that's the critical challenge moving forward to be able to anticipate it in advance and adapt to it so you can minimize the morbidity, you can minimize the mortality and you can minimize the cost associated with the hospitalization and treatment, because that's critical because these threats are not going anywhere. If anything, they are becoming-- going to becoming more frequent. So the challenge to the health community is really to better anticipate and have these early warning systems so you can mobilize your resources or, you know, whatever that may be so we can minimize the burden because we cannot eliminate the threats at this point.
DR. MADDUX: I would just like to thank Dr. Amir Sapkota to joining us on this dialogue session and to help educating us a little bit on both what climate change is and how it impacts our health care system and the people that we're trying to keep healthy. So thank you so much.
Dr. Sapkota: My pleasure. Thank you.