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High heat and health

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Extreme heat events that were once rare are now becoming more common because of climate change. SciLine’s media briefing focused on the physical and mental health effects of experiencing extreme heat for different demographic groups, including children and vulnerable adults such as the elderly and outdoor workers. The panelists discussed trends in deaths, hospitalizations, and other heat-related health outcomes, as well as disparities in these areas and steps communities can take to keep vulnerable people safe.

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MEREDITH DROSBACK: Hello, and welcome to SciLine’s media briefing on extreme heat and health. I’m one of SciLine’s deputy directors. My name is Meredith Drosback, and I’ll be your moderator today. For those new to our briefings, here’s a little bit about us at SciLine. We are a philanthropically funded, editorially independent, free service for journalists and scientists based at the nonprofit American Association for the Advancement of Science. Our mission is simple—to make it easier for reporters like you to get scientific evidence into your news stories. Among other things, we offer a free expert-matching service that connects you with scientists who are both deeply knowledgeable in their field and excellent communicators, all on deadline. Just go to and click on the blue I Need An Expert button. While you’re there, you can also check out some of our other helpful reporting resources.

A few logistics before we start—we have two panelists who will make short presentations before we open things up for questions. To enter a question either during or after the presentations, simply select Q&A at the bottom of your Zoom window, and enter your name, your news outlet, and your question. If your question is for a specific panelist, please be sure to include that information. A full video of this briefing should be available on our website by tomorrow and a transcript within the coming days. But if you’d like a raw copy of the recording sooner than that, please submit a request for that with your name and your email in that same Q&A box. We’ll send you a link to that raw video by the end of today. You can also use the Q&A box to contact SciLine staff if you’re having any technical difficulties during today’s briefing.

So now turning to our main attraction, detailed bios of our speakers are on the SciLine website, so I’m not going to go through those details here. We’ll first hear from Dr. Perry Sheffield, an associate professor in the departments of environmental medicine and public health and pediatrics at the Icahn School of Medicine at Mount Sinai. She’ll share what we know about the impacts of extreme heat on children and what parents and communities can do to keep children safe. And then Dr. Amruta Nori-Sarma, an assistant professor at Boston University’s School of Public Health, will explain what we know about the health impacts, particularly mental health impacts of exposure to extreme heat on adults. And with that, Dr. Sheffield, the floor is yours.

Hot weather and children’s health


PERRY SHEFFIELD: Thank you, Meredith. So—hi, everybody. It’s an honor to be here. And I’m going to briefly summarize what we know about children and the effects of hot weather on their health. It’s particularly salient given the scorching summer that the Northern Hemisphere is having and also in light of the warming trends that we’re seeing because of the changing climate. Some of our funding through our national PEHSU network comes from both CDC and EPA.

So we’ve found that young children—think toddlers, think early childhood, early school-age children—go to the emergency room more often when it’s hot due to a whole bunch of reasons. And they get—when they go, they get a range of diagnoses, and some are very specific to heat, and others are not at all specific to heat, but very common and infuriatingly broad labels of diagnoses for people like me who are trying to do epidemiology work on this, things like general symptoms. So there’s a range that we see. And another way to get at this question or another way to ask this, as we’re thinking about children and heat, is to ask, you know, what’s the burden of heat on children in the United States? And to answer that, you really have to consider a full range of impacts, and you have to think across the broad age spectrum of childhood. And so I just wanted to give a few examples here.

So first, we’ll talk about the most severe—deaths. We know that about 30 deaths per year occur because—inside cars, for children left in cars, generally. And those tragic deaths are thankfully not that common. The much more common deaths usually have nothing specific about heat, though whether or not heat plays a role and how it plays a role is really pretty unquantified so far. So we know there’s missing data there in terms of painting this bigger picture.

The second point there about health care visits—we know, through an article that we published earlier this year, “Warm Season and Emergency Department Visits to U.S. Children’s Hospitals“—we saw that—we estimated that maybe as much as 11% of emergency department visits during the warm months were attributable to hotter temperatures. So that suggests that there’s—that it’s playing potentially a big role in child health.

But the third category here is the subtle health effects. And those—in my opinion, you have to talk about those if you’re thinking about what the overall burden is. And these could include short-term effects, like you get exposed to a hot day and then you have a bit of a stomach ache or you have some learning issues, meaning you’re taking in information maybe not as easily as you might have and it might affect test scores. Sports performance can be affected. But then there’s also a bigger question of longer-term impacts—in utero impacts, kidney damage from repeat exposures to high heat and dehydration. And all of those categories are fairly unquantified. So I give you these three examples to sort of show you that we have suggestions of significant burden but lots of missing pieces in our puzzle.

Furthermore, we know that some individuals are more likely to have health effects when exposed to heat. One example is persons who have a blood condition called sickle cell disease or just one copy of the gene that causes that. So they are considered to have sickle cell trait, which generally we don’t think of as having health effects. But we know that those who are affected, which is thousands of babies born every year in America and up to 3 million people living with sickle cell trait, are at a higher risk of sudden death during exercise in hot weather. Some of the studies around this are around military recruits and—who are going into really intense physical activity at a young age, maybe not acclimatized to that. But we’re also starting to learn that other genetic variations can increase your heat health risks, too. There’s some interesting work around genetic variations that affect muscle contraction and muscle contractility, and that might predispose you to health effects from heat.

We also know that disparities—there are gross disparities in exposure. So many of you are probably familiar with a map that looks something like this. This one’s from the 1930s. It shows the Home Owners’ Loan Corporation designation of desirable and high-risk neighborhoods when they were allotting mortgages. This was largely a race-based designation, disproportionately affecting negatively Black and brown communities. And we know that this type of historic policy and then ongoing policies like exclusionary zoning—they—basically, all the things that contribute to making any area hotter, particularly in cities—so think less shade, fewer green plants, more pavement—all of those things are higher in these areas that were negatively impacted by these policies. And there’s a couple things—like you couple those things with conditions like lower car ownership, greater reliance on public transportation, less access to air conditioning, and those—that’s a dangerous combination, higher exposure to heat.

Our team, in response to this, to try to develop clinical tools that simultaneously educate clinicians—because many of us did not get this in our training—has developed these things that we call prescriptions for prevention. It’s simultaneously educating the clinicians while equipping families with action items. And we’ve created these for a range of ages—pregnant persons, babies, young children, school-age athletes—because it turns out that heat has different effects in each of these age groups. And also, there’s different strategies for protecting yourself or your loved ones.

And so I come back to this idea, this spectrum of effects ranging from death up at the top. And the size of the triangle or the width of it is really meant to represent sort of the number of people affected. And thankfully, in this severity pyramid, death is less common. But there are many important ways that people are still affected. And so we’re slowly coming to understand that heat has these insidious effects. This has been a similar arc through many types of environmental health research. We did it first with chemicals, looking at pesticides. You might be familiar with things like lead. Initially, it was only at very high levels that we thought there were health effects. But now we understand, at much lower levels, there’s impacts. And these can be the subtle health effects or what we might call invisible health effects that you wouldn’t necessarily take someone to an emergency room for. But certainly, when they affect a whole population, it has public health impacts.

And so I leave you with this concept about how we have a long way to go. But there’s these many areas in which heat is potentially playing a role in child health. And so I hope I’ve piqued your curiosity. I look forward to the discussion, and I will leave you with just a couple of resource slides. The PEHSU is the national network, the Pediatric Environmental Health Specialty Units, and it serves as a resource. There are people around the country who are primed to answer questions and provide additional information. And here are my references. Thank you very much.

Hot weather and adult health


MEREDITH DROSBACK: Thank you. And now, Dr. Nori-Sarma, over to you.


AMRUTA NORI-SARMA: Wonderful. Thank you so much, Meredith. And I’m really pleased to be here to share with you some of the work that we’ve been doing looking at the impacts of extreme heat exposures on physical and mental health among adults across the U.S. And I just wanted to start off by acknowledging some of the funders of this work, including the NIEHS as well as the Wellcome Trust.

And I like to start with this figure, which is from the CDC’s Third National Climate Assessment, because I think it does a really great job of explaining all of the different ways in which climate change is impacting human health, including, for example, extreme heat and rising temperatures. But also, it does a great job of illustrating that the health impacts associated with extreme heat exposures and other climate-relevant extreme weather are pretty broad-ranging across asthma, cardiovascular disease, infectious disease epidemics, as well as mental health and a whole host of other health outcomes that are associated with these various climate-related exposures.

And as a little bit of background, we know that seven of the warmest years on record for the continental U.S., the 48 contiguous U.S. states, have occurred since 2015, with 2016 being the warmest year on record. And 2019 and 2020 are now ranked as the next warmest years in our available 141-year record. And we know that climate change is going to lead to more extreme weather events, including, for example, heat waves, but potentially also more extreme storms, increased wildfires, more extreme drought and longer-lasting drought periods. And this is something that we’re seeing occurring in different parts of the U.S. today and in the recent months. And so the particular example that I’m focused on for today, for my talk, is that as climate change leads to more days that see these extreme summertime temperatures, we expect that the burden of both physical and mental health associated with these extreme heat days is expected to increase as well.

And as my colleague Dr. Sheffield touched on briefly in her talk specific to children, but we know the same is true for adults as well, the impacts of extreme heat on physical health outcomes has been fairly well documented. We know that there are primarily two ways that extreme heat impacts health among adults. There are direct effects, which we might think of as being very intuitively linked to extreme heat exposure. And these include things like heat stroke, heat stress, swelling, heat rash, etc. But there are also indirect effects of extreme heat exposure on physical health in adults. And this is because people with underlying health conditions may experience stress because of their exposure to extreme heat that causes issues in those underlying health conditions. So we do see that heat exposure can cause a whole variety of other health outcomes, including cardiovascular illness and renal insufficiency, which is related to dehydration.

But by comparison, the impacts of extreme heat exposure on mental health among adults was relatively less well documented and poorly understood. So our recent study, which I’ve provided a QR code for here in the top right corner of the slide, was trying to look at the relationship between higher summertime temperatures and heat-related emergent or, sorry, mental-health-related emergency department visits during those summertime periods. And I also want to share some of the results that we’ve looked at for potentially vulnerable populations within this group of all adults across the U.S. So we focus on age, gender and different regions in the U.S. as well. So for this study, what we’ve done is looked at county-specific daily maximum temperatures. So this is the hottest temperature each day from the period between 2010 to 2019 for the period—the month of May to the month of September. And we defined the extreme heat as the 95th percentile of this county-specific distribution of temperatures over this historical time period. So you could think about this as approximately what are the five or six hottest days of each summer.

And here I show you what those five or six hottest days look like. And I think the important takeaway from this figure, which is showing you that 95th percentile of temperature for each of the counties across the U.S.—and this is a figure that I’ve drawn from our paper—is that the U.S. is a very climatologically different, heterogeneous area. So we see that the 95th percentile of temperature in the Northeastern U.S., for example, looks very different from the 95th percentile of temperature each summer in the U.S. Southwest and in the U.S. South. And I think this is an important factor when you’re thinking about what are the characteristics of different communities that might make them more or less resilient in the face of extreme heat exposures.

So for our outcomes data for this particular study, we were looking at about 3.5 million emergency department visits across the U.S. for mental health among just over 2 million unique individuals. And this is using a commercial health insurance data set called the OptumLabs Data Warehouse. And it’s among adults over the age of 18, and we include just under 2,800 counties across the U.S. in this analysis. So we have a wide range of—a very diverse patient population included in this study. And here I show you a map of where these emergency department visits are happening. So this is the number of emergency department visits per day in each of these different counties across the U.S. for the summertime periods. And the darker blue indicates places where we have a larger number of emergency department visits. That’s not necessarily saying that the greatest number of emergency department visits overall are occurring in those counties. It could also be that we have more insurance beneficiaries in those counties, for example.

And what we found in this study is that as temperature increased, the rates of emergency department visits for mental health across all of the mental health causes that we’re interested in correspondingly saw an increase. And so here, what I’m showing on the horizontal axis is the ambient temperature. And we’re comparing everything to the lowest temperature that is experienced in the summer. So each of these different ambient temperatures represent an increase from the lowest temperature each summer. And what we have on the vertical axis is the incident rate ratio. So, again, we’re comparing that particular temperature across the spectrum to the lowest temperature in the range. And so what this overall figure is showing us is that as temperatures are increasing, the rates of emergency department visits for mental health are increasing as well. And what we see is that this is true for all mental health causes, and this is also true if you break up all of these emergency department visits by what was the specific cause of mental health for which a patient was seeking emergency care.

So here, we’ve characterized the same curve. So on the horizontal axis, we see the temperature. And on the vertical axis, we see the increases in the rates of emergency department visits as temperature changes. And what we see is that for a whole host of mental health-related outcomes, including, for example, substance use disorders, anxiety, mood disorders, schizophrenia, self-harm, etc., we see that there are increasing rates of emergency department visits associated with increasing temperatures. And this indicates to me that heat is likely to be an external stressor that is exacerbating people’s existing mental health conditions. So if we saw that the rates of increase of these emergency department visits were fairly different across the different types of mental health outcomes, we might expect that there was something specific happening to cause new mental health—mental illness among these patients because of their exposure to extreme heat. But because we see these similar rates across all of these different outcomes that are associated with mental health, we might imagine that people are experiencing stress on top of whatever other characteristics they’re facing that are leading to mental illness in people who already have existing poor mental health.

But what are some of the ways in which we think that heat is contributing to people’s poor mental health? Well, one of the things that we could hypothesize would be disrupted sleep periods that are happening because people are experiencing high temperatures or even daytime discomfort or irritation. And one of the other pathways that I want to mention, which I think is really interesting, is the increase in hopelessness and maladaptive anxiety and stress that people, especially young folks today, are experiencing in anticipation of climate change and the future events that they might be facing as well.

And so what can we do about these issues of the physical and mental health impacts of extreme heat? So as was mentioned earlier, I’m a faculty member at Boston University in the School of Public Health. And so I wanted to pull out the city of Boston’s climate adaptation plan as a great example of a lot of the different ways that cities can work together with communities to try and reduce people’s vulnerability to the stressors of extreme heat and other types of climate-relevant exposures. And you’ll see here from this figure that I’ve pulled out of the Climate Ready Boston Plan that there’s a lot of different activities that the city of Boston has proposed and is in the process of implementing to try and reduce people’s vulnerability to extreme heat, including green spaces and sustainable design and development and, you know, flooding protection and also different infrastructure to improve buildings to try and reduce people’s exposure to heat and extreme cold as well when they’re inside buildings.

And one of my very talented doctoral students, Quinn Adams, has been working on a paper that’s up and coming to look at the locations of cooling centers as another great example of improving resilience among different community members across the country. So this is a map of the identified locations of cooling centers for over 70 different cities across the U.S. And so this is to say that communities and different city planning officials have already started the process of making communities more resilient in the face of extreme heat exposure. And I think that this is one of the great ways that we can start to prepare for and respond to extreme heat events that we anticipate happening into the future. And so with that, I’m really excited to share any other information about any of our results or other work that I’ve been conducting in this area. And I’m very excited for the Q&A session, and I’m also happy to answer any questions by email as well. So thank you. And I’ll turn it back over to Meredith.


What is being done well in press coverage of these issues, and where is there room for improvement?


MEREDITH DROSBACK: Thank you very much for both of those presentations. A reminder to all of the reporters who are with us—to submit questions, please use the Q&A option at the bottom of your screen. To get started, I’d like to ask each of our panelists to briefly address a question about their thoughts on news coverage of the health impacts of extreme heat. What have you seen in the media’s coverage of this topic that has either frustrated or concerned you as an expert on this issue or has impressed you and you’d like … Perry, why don’t I turn to you first for that question?


PERRY SHEFFIELD: Sure. Thanks. I would say that I have been really impressed with some of the visualizations, some of the data visualizations, that I see coming out of journalism writ large, sometimes in the form of storyboards. I think they’re more so—I remember at the beginning of my career, there was creative use. And one example of that is in the redlining that I touched on. And so it is critical to tell the story, to not blame the individuals for a lot of the environmental exposures that are happening or just systematically blame groups of people for being disproportionately exposed. And I think telling the story, showing the maps of the redlining, explaining that arc of how we got from these historical decisions and to situations today, where we have neighborhoods that have much higher micro-urban heat islands that are segregated communities. And so, you know, whole groups of people are getting disparate proportions, but not—because of exposures, but not because of choices that they’re making now because—actually because of choices that were made, in some cases, almost a hundred years ago.


MEREDITH DROSBACK: Thanks. And Amruta.


AMRUTA NORI-SARMA: Yes. So I think I agree with Perry. I’ve been really impressed with a lot of the information that I’ve seen around, how do we conceptualize vulnerability to extreme heat exposure? And, you know, sharing that data and sharing those resources with the general public through the media is, I think, a very powerful tool. And one of the things that I’ve also noticed is that there’s been an uptick recently in the news media reports around extreme heat events that have been happening. And it’s not limited to the U.S. This is a global issue that we’ve seen across the world, especially this year, starting, of course, in the southern hemisphere. The hot season occurs at a different time of year, so it’s in December, January. We saw heatwaves in Australia. We’ve seen them this year in South America. We’ve seen them across the Midwestern U.S. and last year with the Pacific Northwest heat dome in 2021.

And so I really do commend the media for bringing this to the attention of people, not just—what are the dangerous exposures that people are facing? But what are the ways that you can protect yourself? And what are the resources that are available to try and, you know, beat the heat? And I think that one of the things that we could do to encourage people to, you know, improve their resilience in the face of extreme heat exposures is to try and highlight some of these stories even a little bit earlier as we’re going into summertime periods.

So providing warnings about, you know, the potential dangerous impacts of heat exposure and what people could be doing to protect themselves in a time where people who are particularly vulnerable could start preparing for upcoming summertime seasons and having some time to make sure they have—they know where their nearest cooling center is and they know when the cooling centers will be open, for example. Or what are the other ways that they can get access to resources that they might need to protect themselves? So I think that that would be a really great area that I can think of to kind of better our protections during periods of extreme heat, especially for those who are most vulnerable.

What are the best metrics to track health and economic impacts of extreme heat?


MEREDITH DROSBACK: Thank you. We have a question from Brittani Howell at Side Effects Public Media. Brittani asks, if we are trying to show the health impact of extreme heat at the local or city level, what metrics are best for us to look at? Brittani asks, similar question for economic impacts of extreme heat, what metrics should they be looking—should reporters be looking for to track and quantify and communicate the burden and impact of extreme heat?


AMRUTA NORI-SARMA: Go ahead, Perry.


PERRY SHEFFIELD: Yeah. Well, I think, stay—one, so on the second question first about the economic valuation—it’s probably not very satisfying, but I say, stay tuned. I know that there’s, like, plans in the works with some very stellar researchers, not myself or my team, who are starting to look into that to better quantify it. And it’s basically—the gist is, we have to have pretty solid epi—epidemiology research to be able to understand what our dose—we say, our dose response function is. And then we can start to unpack, particularly if we’re forward-looking. The question wasn’t necessarily about future projections. But we have pretty good future projections of what we think the temperatures are going to be in—you know, in New York City, for example, or how many hot—extremely hot days we’re going to have. And so it’s a matter of putting those numbers together. And actually, I will say, this is—you don’t have to stay tuned for that long. New York state is working on their—on an updated climate impact assessment. And as part of that is an economic impact component. And then, Amruta, I don’t know if you want to jump in there.


AMRUTA NORI-SARMA: Sure. So I think that the first question—sorry, Meredith. If you don’t mind refreshing, the first question was on, how do we best measure what the health impacts are for heat exposure? Like, what are the best ways to measure it directly?


MEREDITH DROSBACK: Particularly for reporters, if they want to demonstrate the health impact…




MEREDITH DROSBACK: …At the local or state level, what metrics should reporters be looking for?


AMRUTA NORI-SARMA: Yeah. So I think that’s a really great question. And it can be really difficult to do because of a few different things that we see from the academic side and, as Perry was mentioning, from the epidemiological perspective. And the first is that there’s no really consistent definition for what a heat wave is. So a lot of different people will characterize what a heat wave period is differently. Like, the National Weather Service has their own version of a heat forecast, and it might be different depending on what part of the country you’re in. It might be different depending on what are the particularly vulnerable populations that you’re looking at in different cities or in different rural versus urban areas? And so it can be a combination of, here’s the temperature that we’re worried about, and here’s the number of days of the heat wave that we’re worried about. So that can make it very complex. And it’s not just for reporters that it’s complex. It’s also for public health practitioners as well. It becomes very complex to measure these issues.

And then also, there’s been a lot of dialogue and discussion about the best way to measure the health impacts of extreme heat exposure. So you could think of looking at the number of people who die on any given day as a good measure of the impacts of the heat. Of course, you know, people are born and people are dying each day. So that’s part of a constant cycle. And so it’s about measuring the difference on heat wave days versus not a heat wave day. And then you can think about hospitalization—so getting data from hospital registries. And you don’t necessarily have to limit it to those specific heat-relevant causes that I mentioned, because we know that heat can cause stress for people who have underlying health conditions. So even things that might not get automatically picked up as a heat-related illness might actually be somebody who experienced an exacerbation of their health condition because they were also exposed to extreme heat.

So you could just look at the total number of hospitalizations or the total number of emergency department visits for different causes, as we did. And that data—generally you can get it from different local hospitals. I think different hospitals will have different reporting procedures. So what is the time scale? I’m not entirely sure. There might be daily counts or there might be weekly counts, so depending on what the local resources are that are available. So I think that can be one of the valuable things to look at, is counts of emergency department visits or counts of hospitalizations during heat waves compared again with non-heat wave periods.




AMRUTA NORI-SARMA: But it’s not a simple issue, and I don’t know that anyone has the ideal solution for it.




PERRY SHEFFIELD: And I would just echo that—what Amruta was touching on, that if we are going to talk about heat-associated illness or heat-associated deaths, sometimes they’re not—they don’t have that in the title. And so you have to ask—if somebody’s giving you a number, you have to ask what they were including under their umbrella.




PERRY SHEFFIELD: And so the methods that Amruta was talking about, if you’re—it’s great to look at excess mortality or excess death during a specific event. That’s a big umbrella, and that’s probably getting closer to some measure of accuracy, as opposed to looking at things like heat exhaustion or heatstroke, which is a very narrow pinpoint on probably the big picture.


AMRUTA NORI-SARMA: Yeah. Not to mention that if you’re focusing on heat stress or heatstroke, there’s a little bit of a chicken and egg problem there. Like, did people have heatstroke added to their diagnosis because the doctor knows that it’s hot outside, or is it because they truly were suffering from a heatstroke? I’m not necessarily saying that that happens very often, but it’s always a question that we have. So I think looking at the total number can try and eliminate some of that potential for bias that we might see in those numbers.


What share of child ER visits are associated with hot weather?


MEREDITH DROSBACK: Perry, I have a clarifying question for you about one of the statistics you mentioned. This is coming from Nick Gerbis at KJZZ Public Radio in Arizona. Nick says that you mentioned that 11% of visits to ERs and children’s hospitals occur during warm months, but warm months make up 30 to 50% or so of the year, depending on where you live. So Nick is wondering if that number seems low. Or are you saying that in warm months, 11% of children’s ER visits are for health-related illnesses?


PERRY SHEFFIELD: Yeah. Let me try that again because I probably muddled it. What I was trying to say is that during—so our study looked at the warm season, and what we found was that during our study period, we think that higher temperatures accounted for about 11% of those visits that we saw. So I agree with all those points that were made in the question. It’s not the full year, but it was during the season in which we expect the temperature would actually play a role in—a risk factor. And so of those summer months, basically, 11% of those visits are probably because of slightly higher temperatures, not necessarily extreme heat. And that’s another point maybe we’ll come back to. But I mentioned child deaths in cars, which is a serious, you know, obviously incredibly tragic event when it happens. But temperatures in cars can get deadly hot when an outside temperature is under 70 degrees Fahrenheit. So it doesn’t—again, it doesn’t have to be during heat waves or extreme heat events that there’s a risk to health from heat.

Do data on high heat and ER visits for mental health include patient demographics?


MEREDITH DROSBACK: Thank you. And, Amruta, also a clarifying question for you, this one from Larry Johnson from the Cobb County Courier—Larry asks, did the county-level data you used to determine increases in mental health emergency department trips have other demographic characteristics included, such as race or income level?


AMRUTA NORI-SARMA: That’s a great question. And due to patient confidentiality in these protected health care records, we actually don’t have a lot of individual-level identifying information. But I want to make one point, which I think is relevant to this question that’s a very important one, which is that in a couple of senses, there are some pretty severe limitations to this study that I’ve presented today. And the first one is that we’re only looking at people who have commercial health insurance. So we can anticipate that we’re missing out on a really vulnerable subpopulation across the U.S., which is adults who are living with low insurance or who are uninsured or who are publicly insured. And so that population wouldn’t be captured in our data. And so I think we can assume that this is an underestimate of the actual burden for mental health illness associated with extreme heat exposure.

And then the second thing that I want to mention, which I think goes back to maybe a discussion that we had earlier, is that what we’ve done here is looked at emergency department visits, but there’s a whole host of mental health outcomes that are short of someone needing to go to the emergency department. Or as Perry was mentioning during her presentation, there’s a lot of, you know, very subtle mental health issues that might occur as a result of exposure to heat, exposure to other stressors. And we haven’t captured those in our dataset either. We’re only looking at the most extreme interactions between a patient and the health care system, which is the emergency department visits. So I think in a couple of different ways, we’re likely underestimating the burden that’s associated with heat exposure for people experiencing adverse mental health.

How are outdoor workers affected by high heat?


MEREDITH DROSBACK: Great. This is from Melissa Feito from Florida Public Radio. Melissa asks, we have a lot of construction and agriculture workers in the state of Florida who face long hours in the heat. How may people who work regularly in hot conditions be affected long term? Certainly, we expect with climate change that these hot conditions are going to continue.


AMRUTA NORI-SARMA: That’s a—oh, sorry, go ahead, Perry.


PERRY SHEFFIELD: No, go ahead.


AMRUTA NORI-SARMA: That’s a really great question. And I think that’s been the topic of conversation for a lot of different colleagues of mine who study occupational risks. And I think that it’s certainly the case that people have potential for a very high occupational exposure to heat, either because they’re outdoor workers or because they work in non-ventilated or un-air-conditioned spaces as well. So I think there’s a couple of different pathways that we know people can be exposed through their occupations to higher heat. And I think that we can anticipate that we could see—increases in injuries is one of the items that I’ve seen being hypothesized as a potential outcome of higher heat exposures in the workplace. People become a little bit—you know, they start to experience some symptoms that might lead them to have injuries on the job or be a little bit less able to carry heavy items, I think is another concern if they’re dehydrated or don’t have enough water. And so I think there are a couple of different practices that I’ve seen implemented as part of heat adaptation plans to try and make workers less susceptible during extreme heat periods.

So one of the solutions is, you know, encouraging more frequent water breaks during hot periods, encouraging workers to sit down and take a few minutes of rest every—you know, periodically to make sure that their heat exposure is reduced. For people who work outside, providing some sort of shade where they can rest during the hottest parts of the day—this has been, you know, a really excellent tool to reduce the health effects of extreme heat exposure. And another one that’s been proposed that I think has been a very successful program is to actually eliminate the hottest—the working hours during the hottest part of the day and instead have people start early in the morning and maybe work a little bit later in the evening when things might have cooled off or the heat might not have picked up as much, so that people are still working the same hours, but—and having the same levels of productivity but maybe not working in those extremely hot mid-afternoon periods. And then, you know, again, for outdoor workers, of course, drinking water is crucial, so providing shade and providing drinking water.


PERRY SHEFFIELD: The National Institute for Occupational Safety & Health, NIOSH, has an app that’s aimed to empower workers, but also to educate employers about the risks of heat and send them alerts when there’s high heat days and to give them safety precautions like Amruta was just sharing. We have started to see, particularly in other parts of the world but now also here, what we think is heat-associated kidney disease. And we think that repeated dehydration events plays a role in that damage to the kidneys. We don’t know if repeat dehydration events has cognitive or mental health effects yet. Cardiovascular, respiratory—it could play a role in all of those, but I think more research is being done.


AMRUTA NORI-SARMA: Yeah. That’s one of the things that I think we found as well in our study, looking at physical health impacts of heat exposure in this similar population that I described for the mental health work. But we did see increases in emergency department visits for renal insufficiency, which I think I mentioned. Yeah.

What are the best data sets to quantify health impacts of high heat?


MEREDITH DROSBACK: We’ve had a few questions from reporters on data sets and access to data, so I want to pose one of them to you here. This is from Rebecca Johnson from KESQ-TV in Palm Springs. Rebecca asks, in efforts to report on heat impacts on health, reporters are challenged by the data recording since, as you alluded to, Amruta, already, many deaths and hospitalizations that could be compounded by extreme heat may not be officially marked as being heat-related. What datasets do you recommend for finding this information?


PERRY SHEFFIELD: Real-time data is hard to come by, partly because of what Amruta talked about with the HIPAA regulations around that—but probably some strategic partnerships with departments of health that have surveillance systems because that’s going to be the fastest data. New York City is an amazing data landscape. And we—after 9/11, they have bioterrorism surveillance systems in place, and they get twice daily downloads of drugstore receipts looking at specific types of medications that people are checking out. And that hasn’t been—to my knowledge, we’ve used it for things like pollen and allergies, but it hasn’t been used for heat. But it has incredible potential is the point. And it has—and they also get emergency department, you know, presenting symptoms and things like that. And so they can see upticks basically same day, and they have data, and they’re processing it that fast. So in that case—not that I or a journalist could necessarily see that data. But if—but with the right partnerships and the right communication and the right sort of aligned priorities about getting out heat messages, which is often a priority of health departments, you might be given indirect access to that kind of information.


AMRUTA NORI-SARMA: Yeah. I was going to say the same thing. Because of the issues around patient confidentiality and around other, you know, deidentifying patient data in order to be able to use it for the type of research that I’ve presented here, there’s a pretty substantial time lag that makes it just not feasible for real-time communication to the public. So I absolutely agree with Perry. I think the key is to develop strategic partnerships.

And one of the things that I want to mention is that, you know—I mentioned the climate adaptation plan for the city of Boston. I think a lot of cities and, as Perry mentioned, a lot of departments of public health—sending out alerts to the public that we are expecting days or a period of extreme heat is a key central component of the heat adaptation activities, making sure that the messaging is getting to the folks who could benefit from it the most. So I think, you know, there’s kind of a win-win situation here that I think could be beneficial for the media, for the public, for the departments of health that are potentially looking for partnerships to try and publicize information about heat wave periods more broadly to the general public. So I really do encourage development of those key partnerships.


PERRY SHEFFIELD: Two more points I want to make about this data question. Hospitals increasingly are using electronic health records or electronic medical records, and so often there’s a potentially quicker turnaround time. Some hospitals are already automating alerts to patients that they have deemed vulnerable for a number of different things, like a, you know, high wind event or hurricane is coming and that type of sort of disaster preparedness. And so heat is in lockstep with that. And I think—I’m not aware of a hospital system using that yet, but journalists raising the question or posing it or finding out about another city that’s doing it and challenging your local hospital system or health system to think about that would be great and possibly a motivator.

And then if you have the luxury of time or working on longer-term projects, there is lots of data available. And depending on what kind of analytic skills you have—or you could look at sort of events-based views, like Amruta was saying. We—for our research, we use—one of the projects I worked on uses a New York state data set that—to get very detailed data, like where patients live, you have to go through lots and lots of hoops, but they publish composite data online, and it comes up through within a few years of now. So again, if you’re looking retrospectively—and many states or, increasingly, municipalities have that kind of data that they’re making available. And in that case, it’s claims data or administrative data records. So those are the things you’re asking for. And it usually is governed by the local health department or the state health department in our case.

How does sickle cell trait correlate with heat-related health concerns; what other groups are at high risk during hot weather?


MEREDITH DROSBACK: Great advice. Perry, this is another follow up question for you, this time from Keneisha Deas from FOX54 News in Huntsville, Alabama. Keneisha asks, you touched on people diagnosed with sickle cell who have higher risks of heat-related illnesses. Can you share a little more about why they are at higher risk and what other groups of people might also be at higher risk?


PERRY SHEFFIELD: Yeah. Well, we know that people who have sickle cell disease, so two copies of the same thing—they have the full manifestation—are exquisitely sensitive to being dehydrated. And that has to do with the way the wall of the red blood cells are constructed and what happens when they are in stressed conditions. And they change shape which can cause clotting, effectively, and microclotting and can affect multiple organ systems. And so not being a hematologist—but making a little bit of a transition there to having a sort of a more mild form of that. We used—I mean, when I came through medical school, we were taught that sickle cell trait was a concern if you had a baby with someone else who had sickle cell trait because then your child might have the disease. But what we now understand, kind of along the lines of what I was saying—usually, we start with the big effects, and then we start to understand the subtle effects. And so we now know that people with trait have generally lived normal lives, but in certain conditions like these—being exposed to extreme heat, might have a risk of—higher risk of health effects, probably because it’s a similar mechanism along the way the red blood cells work, the hemoglobin.

And then and—oh, in terms of other groups, this is an area that we’re starting to unpack a little bit. We did a study looking at children with chronic disease—other chronic disease conditions. And in some cases, even though we know physiologically they are more at risk if they’re dehydrated, we actually saw in our data in terms of emergency room visits and hospitalizations that during hot weather, they had less visits, they were protected. And we think that’s probably a phenomenon of being a child, being protected, being—having caregivers that know that it’s hot out and know that you’re not supposed to go out then. And so there’s actually a—probably a compensatory protective effect, even though we think that some of those groups, if they get dehydrated or are in high heat conditions, need to take special precautions.

So that’s—we’re not—if we had reports from the family, for example, or other mechanisms of figuring out if they had to increase their medications or other more sensitive things, we might be able to see a signal with that. And then I touched a little bit in the presentation on genetic variants that they’re starting to unpack—not my area of research, but an interesting one for sure as we start to understand that there’s just—there’s a lot of genetic variability. And we are—in some cases, but I think the example I gave had to do with muscle contractility. And so it’s certain—under certain conditions, certain people’s bodies will respond differently.

How can mortality from high heat be quantified?


MEREDITH DROSBACK: Thanks. We have another data-related question, this time from Ciara McCarthy with the Fort Worth Star-Telegram. Ciara says, how would you evaluate our knowledge regarding the number of deaths that are caused either directly, like heatstroke, or indirectly, like cardiovascular deaths, by heat? Do we actually have a reliable number?


AMRUTA NORI-SARMA: That’s a great question, and it’s one that we’ve been working on for a while. And I think we have a range of numbers. I don’t know if we have the right number. I’ve seen some reports of—using mortality registry data that attribute, I think it was 5,000 deaths over the period from 2004 to, I believe, 2013 or 2014 across the U.S. That’s from one study. So I think the short answer is no. I don’t think we have a very good estimate of the number of deaths that are attributable to extreme heat. And it’s for some of the reasons that we’ve mentioned before—that we don’t have good measures of what the actual outcomes are. We don’t have recent enough data that we can use to try and answer this question. The data are all lagged. I think even estimating what is the attributable number is a complicated question that we probably will continue arguing about for a while in academic circles.

But I think that a lot of people are doing a lot of really excellent work to try and understand what the elevated risks are of extreme heat. And so I think that’s the—you know, for now, I think that’s the best way that we have to characterize the health impacts of extreme heat exposures. And, you know, if you look in the literature, you’ll pretty easily be able to find some of the papers that I’m mentioning here. And searching for attributable numbers is the easiest way to bring those up if you’re looking for what are the spectrum of estimates of attributable number or attributable fraction—excuse me—of deaths attributable to extreme heat exposure.


What other underlying health conditions pose a risk during hot weather?


MEREDITH DROSBACK: Another follow-up for you, Amruta, again from Keneisha Deas at Fox 54 in Huntsville. You mentioned that heat can cause stress on people with underlying health conditions. Can you give some examples of the types of underlying health conditions you’re talking about?


AMRUTA NORI-SARMA: Sure. I think it’s some of the ones that we’ve mentioned maybe in some of the previous questions—so people with cardiovascular disease, people with renal insufficiency. I think we’ve seen increases in emergency department visits for a few other outcomes. I believe respiratory illness was among them. I think that we’ve also looked at—there have been some studies that have looked at people who are in treatment for different cancer outcomes and so they might be on medications. And I think that maybe there’s some combination of medications that people are taking plus extreme heat exposure that might lead to elevated risks of adverse health outcomes. So those are some of the things that I’ve seen previously. But I’m sure there’s a whole spectrum of other chronic health conditions that are associated with—the adverse events are associated with extreme heat exposure. And Perry might have some other examples as well, I think, among children. I think you mentioned a few already, but…


PERRY SHEFFIELD: Yeah, we’re definitely still trying to unpack that. And as I said, some of the findings have been surprising in terms of—but we think that that is because children have more social protections, which is good news, right?




How do people know if they have sickle cell trait?


MEREDITH DROSBACK: One more follow-up for you, Perry, on sickle cell. This is from Karen Bouffard from The Detroit News. Karen asks, are people with the sickle cell trait likely to know they have it, or would they only know if they had genetic testing? Karen’s wondering if the Black population generally would be more likely to suffer heat risk due to the prevalence of this trait.


PERRY SHEFFIELD: So if somebody was born here in the last decade plus—I don’t have my numbers quite specific. But when—since we’ve been doing newborn screening, we do screen for hemoglobinopathies. And so yes, they should know. That wouldn’t necessarily include the immigrant population. The prevalence is higher in people with African ancestry, though the prevalence in any people with—any groups of people with ancestry from areas that had endemic malaria is elevated. And so—and many of those people might not consider themselves or be documented in a medical record as Black-presenting. And so it could have—it has wide-reaching impacts across the population. And it—and knowing whether or not you have it is probably dependent on where and when you were born in terms of what kind of testing was done.

What is one key take-home message for reporters covering the health effects of high heat?


MEREDITH DROSBACK: Great. I want to close this afternoon by asking both Perry and Amruta to offer our reporters a final thought. If there is one thing you really want journalists to think about or to include as they consider putting together stories on this topic, what would it be? So Amruta, I’ll turn to you first this time.


AMRUTA NORI-SARMA: Great. I think that in thinking through all of these physical and mental health impacts of extreme heat, it’s easy to go into all of the damages and all of the consequences that people face as a result of higher temperatures. But I think I’ve also tried to highlight some of the ways that different communities are coming together to try and provide better resilience in the face of extreme weather exposures.

And one of the things that I didn’t have a chance to mention, but I think anecdotally in my time as a person working in this field and in my experiences and talking with different community members—time and time again, we see that the social ties that people have is one of the best protections that they have against the adverse health effects of extreme heat—so friends checking in on friends, neighbors checking in on neighbors, making sure your loved ones are OK during these extreme heat waves. And, you know, as we’ve shown, there are some protective effects of parents taking care of their children during extreme heat. And it’s just, you know, these types of social bonds that we have that I think are going to be really powerful to try and protect different vulnerable members of our communities from the adverse effects of extreme heat.


MEREDITH DROSBACK: Thank you. And Perry.


PERRY SHEFFIELD: I have been very inspired by the questions that were asked, and I was also just struck by that and how often just asking the questions can be so powerful. So I think a lot of what we’ve said today has ended with, we need more information. We’re still working on that. But it—I think by telling the story of even to the edge of what we know is powerful and then telling the story of what we still need to know in order to be able to answer those questions. Journalists are so good at taking that step back and being like, so why do we care? Why does this, you know—why should the public care about this? And so thank you to the journalists and that—and to a charge to keep doing that and using that murky and sometimes frustrating unknown area as the area of the edge to advance.

And I would echo the point that Amruta made about some of the powerful things that we do see happening in the social networks. Getting the information—we know that with the highly mobile populations we have in the United States and coming from elsewhere, sometimes people are in new climates, and they might not understand the heat risks that they’re experiencing. And it might be because they grew up in a warm environment, and they think they can handle it. Say, they came from the islands, and they can think they can handle it in New York City, and they don’t want to, you know, have to pay the extra energy bill. And so that’s a whole confluence of things that takes some policy to try to, in some cases, subsidize summertime energy bills, which is being worked on. But it also takes neighbors sort of checking in on people and making sure that they’re staying safe and also just recalibrating that this is not your grandfather’s climate that we’re living in anymore. And particularly in hot, dense cities, it’s—they’re not built for the heat. And so we have to take extra precautions and help keep each other safe. So telling that story is really important.


MEREDITH DROSBACK: That’s all the time we have this afternoon. I want to thank both Perry and Amruta for so generously sharing their expertise today. And thank you to the reporters for listening and exploring ways this information might be relevant in your communities. To the reporters, as you log off today, you’ll see a prompt for a short survey. Your feedback on these surveys really does help us to plan and redesign these briefings to be most helpful to you. So please take just a minute to answer those questions and let us know what you think. SciLine’s next media briefing is just a week away. We’ll be talking about community resilience to wildfires with a focus on buildings, water infrastructure and land use. You can sign up at our website, and we hope to see many of you there. As always, please follow us on Twitter at @RealSciLine and make sure that you’re registered with us, once again, at to be notified about other upcoming events. Thanks again, and have a great afternoon.

Dr. Amruta Nori-Sarma

Boston University School of Public Health

Dr. Amruta Nori-Sarma is an assistant professor in the environmental health department at Boston University School of Public Health, where she studies the relationship between environmental exposures associated with climate change and health outcomes in vulnerable communities. Her previous work has examined the impact of heat waves and air pollution on health in vulnerable communities in India, South Korea, and across the U.S. Her current research aims to understand the impacts of interrelated extreme weather events on mental health across the U.S., utilizing large claims datasets. She also has an interest in evaluating the success of policies put in place to reduce the health impacts of climate change.

Dr. Perry Sheffield

Icahn School of Medicine at Mount Sinai

Dr. Perry Sheffield is an associate professor in the departments of environmental medicine and public health and pediatrics at the Icahn School of Medicine at Mount Sinai in New York City, where she co-leads the children’s environmental health team.  For the U.S. EPA Region 2 Pediatric Environmental Health Specialty Unit serving New Jersey, New York, Puerto Rico, and the U.S. Virgin Islands, she leads the Caribbean initiative.  Her research focuses on the health effects of climate change with a focus on children and climate justice. Current work includes exploring children’s vulnerability to heat.

Presentation: Dr. Amruta Nori-Sarma


Presentation: Dr. Perry Sheffield


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