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Each week, Health Affairs' Rob Lott brings you in-depth conversations with leading researchers and influencers shaping the big ideas in health policy and the health care industry.
A Health Podyssey goes beyond the pages of the health policy journal Health Affairs to tell stories behind the research and share policy implications. Learn how academics and economists frame their research questions and journey to the intersection of health, health care, and policy. Health policy nerds rejoice! This podcast is for you.
As listeners may know, this month marks the release of a new theme issue of Health Affairs Journal dedicated entirely to climate, health, and equity. Now, one question we're always asking when evaluating research and thinking about what to publish is, does this article expand the base of evidence that policymakers may turn to in any given field? And so we're especially excited because as a collection of articles, this month's theme issue does exactly that. Many of these studies deepen our understanding of the ways that climate change affects health. But then they go even further to illuminate which people and which communities may feel the impact more deeply or more acutely than others.
Rob Lott:And that's the subject of our podcast today. I'm here with Doctor. Dara Patel, a primary care physician and research fellow at the Cambridge Health Alliance and Harvard Medical School. Together with coauthors, she has a new article in the May issue of Health Affairs. Its title is, quote, cold related illness in an era of extreme climate events, US trends 1998 to 2022.
Rob Lott:It's a really very interesting article. It begins to fill important gaps in the evidence base that policymakers could use to guide next steps at the intersection of climate and health. And I can't wait to dig in. Doctor. Dara Patel, welcome to our Humble Podcast.
Dhara Patel:Thanks so much for having me, Rob. I'm excited to be here.
Rob Lott:Well, let's start with some context. I know you're a doctor, not a climate scientist, but this is a really interesting study at the intersection of those two fields. And so maybe you can tell us a little more about how climate change leads to extreme cold events.
Dhara Patel:Yeah. It's a great question because at first glance, it doesn't seem like an intuitive link. We commonly equate climate change with rising global temperatures, which is true. Mean temperatures are rising. At the same time, though, climate change doesn't eliminate the cold.
Dhara Patel:It changes weather patterns. So severe cold snaps can still happen and sometimes in places that aren't used to dealing with them. Part of the reasoning is that the polar vortex, which is a band of cold, frigid air that lives near the Arctic year round, can periodically become unstable due to rapid warming of the Earth and the Arctic region. And that allows very cold air to escape and plunge southward, creating these temperature drops and cold snaps in places that usually have more moderate temperatures. So just to make that tangible, this past winter gave us a clear example of that paradox.
Dhara Patel:January 2026 was warmer than average nationally, but still produced a dangerous cold storm with widespread snow and ice, power outages, and Arctic outbreaks reaching the Deep South in Florida. And you might remember the Texas winter storm of twenty twenty one that led to massive power outages, water shortages, and an estimated three hundred to up to eight hundred deaths. So while average temperatures are rising, climate change can still create the conditions for dangerous cold snaps, which is why extreme cold remains a serious health threat in a warming world.
Rob Lott:Great. And so tell us a little bit about how that affects health. Your paper uses the term climate related illness and cold related illness. And tell us how those sort of, how do you define those terms and what do they mean for your your study?
Dhara Patel:Yeah. That's a nuanced question because there's a narrow research definition and a broader clinical and public health definition. So in studies like ours, we utilize ICD codes that identify medical conditions directly related to climate exposure, such as heat cramps, heat stroke, hypothermia, meaning low body temperature, or frostbite, for example. Those are diagnoses that are most clearly and immediately attributable to the climate. But really those aren't the only conditions considered to be climate related illness.
Dhara Patel:They're only part of the picture. Climate related illness also includes many other health conditions that are triggered or aggravated by exposure to extreme weather. So for example, prior studies have shown that extreme heat or cold can cause an acute worsening of cardiovascular diseases, respiratory diseases, and psychiatric conditions, just to name a few, often enough to require hospitalization. So someone may come to the hospital with an asthma exacerbation or a mental health crisis that was precipitated or made worse by the weather, even though the chart doesn't list a climate specific diagnosis code. So you can think about climate related illness in two layers.
Dhara Patel:There are the direct effects of weather exposure like hypothermia or frostbite like we used in our study. And then there are the indirect effects where extreme weather aggravates underlying diseases, which can be equally dangerous. Most studies focus on the direct effects of weather exposure, but the true health burden is actually much broader than that.
Rob Lott:And so what do we know about the prevalence? Or I would say prior to this study, what did we know and kinda how did that inform your steps as a researcher?
Dhara Patel:Before this study, we already had evidence that the general health burden of extreme cold temperatures in The US was substantial and growing. On the mortality side, prior studies have shown that deaths due to extreme cold temperatures have been rising with extreme cold actually causing more deaths in The United States annually than heat. On the morbidity side, there is research showing that extreme temperatures drive people to the emergency room and require many to be hospitalized due to illness severity. But most prior studies for cold were small. And based on analyses on individual cities or states or specific subgroup populations and typically over shorter periods of time.
Dhara Patel:And so we didn't know what the national burden of CRI hospitalizations or cold related illness hospitalizations was or how that's evolved over time in the context of climate change or how that burden is distributed across different groups based on potential vulnerability. And that's what our study aimed to examine.
Rob Lott:Great. Well, so against that backdrop, you kinda had a sense of where things were heading. But as you say, this is sort of the first nationwide take on those hospitalizations. You looked at it over the period, a pretty broad period from 1998 to 2022. What are some of your top line findings?
Dhara Patel:So we had analyzed a national dataset that represented all US hospitalizations between 1998 to 2022, as you mentioned. And we focused on the months of October to April annually, which are traditionally considered the colder months based on previous studies. Our main finding was that despite rising temperatures on average, the CRI hospitalization rate has risen dramatically in The United States over twenty five years. In fact, it's tripled. Second, we found that the patients most affected were those with psychosocial vulnerabilities.
Dhara Patel:So those experiencing housing insecurity, those living in high poverty neighborhoods, and individuals with substance use disorders or mental health conditions. That highlighted to us a clear socioeconomic gradient that's linked to increased vulnerability of extreme weather exposure. Our study also showed that cold related illnesses are serious. Once hospitalized, these patients faced a four times higher in hospital mortality risk compared to all other inpatients combined. One last important finding was that cold related illness isn't confined to traditionally colder regions.
Dhara Patel:So while the Midwest and West saw some of the steepest increases, cold related illness hospitalization rates rose in every region, including the South, which suggests that cold related illness is becoming a broader national issue, including in areas that may be less prepared for when extreme cold does occur. And I'll caveat, Rob, that our study focused only on hospitalizations coded with cold specific ICD codes, as we mentioned earlier. So hypothermia, frostbite. That means we didn't capture the likely many other hospitalizations that were triggered or worsened by cold exposure, such as cardiovascular or respiratory events. So based on that, our findings are likely an underestimation of the true health burden of extreme cold.
Rob Lott:Got it. Wow. Well, some pretty, stunning findings there. I wanna look under the hood a little bit, with you in just a moment. But first, let's take a quick break.
Rob Lott:And we're back. I'm here with Doctor. Dara Patel, a primary care physician and research fellow at the Cambridge Health Alliance and Harvard Medical School, talking about a new research paper in the May issue of Health Affairs about cold related illness in an era of extreme climate events. Events. And that those, the rates of cold related illness, your study found, really rose dramatically.
Rob Lott:And as you said, there's this sort of socioeconomic gradient. And I'm wondering if you can sort of paint us the picture, I realize that these are population level numbers and every situation is unique, but I'm imagining individuals who might sort of already be vulnerable living in sort of the margins and struggling with a substance use disorder, some sort of serious mental illness, and it's this extreme weather event, this cold snap that sort of pushes them over the edge from vulnerable to actually hurt and in many cases hospitalized. Is the factor there the increasing frequency of these cold events? Or is it that there are more people kind of living on the margin and therefore more vulnerable? And how do you think about those factors interacting with each other?
Dhara Patel:I think it's an intersection of both. So one of the key ideas behind our study is that cold related illness isn't just about the temperature itself. It's also about whether people are able to protect themselves from exposure. And so just to explain the reasoning of some of those conditions we chose, based on prior local and regional studies, we focused on psychosocial vulnerabilities that can directly limit a person's ability to stay warm, recognize danger, or seek help early. So for example, we looked at substance use disorders because alcohol and psychoactive substances impair body temperature regulation and judgment.
Dhara Patel:We also looked at specific mental health conditions, including dementia and intellectual disabilities because cognitive and psychiatric illness can make it harder for someone to recognize symptoms, care for themselves, or access shelter and medical care in time. And housing insecurity is another major factor because people without stable housing may face prolonged exposure to cold environments and may have limited access to safe indoor spaces or reliable heat. And importantly, these risks often overlap. Someone experiencing homelessness may also be living with a substance use disorder or a serious mental health condition, which can all compound their vulnerability.
Rob Lott:Can you say a little more about sort of the potential interventions that someone might take at the local level when they sort of think about this context here? And so I live in Chicago. We obviously are no stranger to cold snaps, and I know, you know, well when in the January when we have one of these instances, the city rolls out their warming centers, and maybe they find additional shelter beds and that kind of thing. And obviously, there's this sort of immediate desire to protect people from, you know, hypothermia and that kind of thing, particularly folks who might otherwise be without shelter and without a home. And do you have a sense of how folks in that sort of public health role, that sort of city led or municipality led role are thinking about the health impacts?
Rob Lott:Is it just let's get people as protected as possible as quickly as possible? Or is there sort of a more broad systemic approach to handling moments like this?
Dhara Patel:There are immediate public health interventions, which I do think we see already, but maybe we're not seeing them in all regions in The US. And our study shows that we do need to be thinking about them everywhere in The United States. And so from a public health intervention standpoint, there are ways to expand our cold weather resilience, whether that's expanding emergency shelter capacity during severe weather, improving cold weather outreach and warning systems when cold weather is supposed to occur in the area, and strengthening coordination between health systems, social service organizations, public health agencies so people don't fall through the cracks. But I do think even going beyond the public health level, we should be focusing on other policy interventions. One of the most important implications of our study is that these risks are not fixed.
Dhara Patel:They're shaped by policy. Cold related illness is influenced by whether people have stable housing, reliable heat, access to behavioral healthcare, and access to health coverage. Those are all areas where policy can make a real difference. And so at the broadest level, we need to still focus on strong environmental and public health protections. Even if federal progress is limited right now, reducing greenhouse gas emissions is essential to mitigating climate change and limiting the weather variability and extreme volatile weather patterns that we know are contributing to climate related illness.
Dhara Patel:From a health perspective, policies that weaken emission standards or roll back foundational climate protections move us in the wrong direction. At the same time, there is a lot we can do right now to reduce exposure and protect the people at greatest risk. One major area is energy and security. Expanding utility assistance programs like LIHEAP can help households afford safe indoor temperatures during both winter and summer. Another is housing.
Dhara Patel:Increasing access to stable and affordable housing would directly reduce prolonged exposure to dangerous cold. We also need stronger behavioral health systems because untreated mental illness and substance use disorders can make people much more vulnerable during extreme weather. And I'll note that health coverage matters too. Many of the patients that were most affected in our study were covered by Medicaid or were uninsured. And Medicaid is especially important because it helps support behavioral health treatment and management and provides the ability to have routine medical care, all of which can reduce risk.
Dhara Patel:So from a public health standpoint, maintaining and strengthening access to health care coverage for all is part of climate adaptation too. So ultimately, I think the answer is that we need action on both fronts, long term climate policy to address the root cause and targeted social health and public health policies to protect the people at greatest risk right now.
Rob Lott:Do you have a sense of the sort of impact of basically the story that you're telling with this paper? Does the public understand or sort of appreciate just how dramatically these numbers have changed over the years?
Dhara Patel:It's a great question because, you know, even anecdotally, when I mention our study and that cold related illness hospitalizations have tripled in twenty five years, the first question I get is, but I thought temperatures are rising. And it's and it's difficult to make that link between climate change, global warming, and cold events. But, you know, I recently saw a survey online that said, I think sixty to eighty percent of people have experienced cold weather in the last five years. So we're all experiencing it, but it's difficult sometimes to make that link with climate change. But I will say, you know, what our research suggests is that the burden of cold related illness is growing and that that growth isn't random.
Dhara Patel:It's concentrated in populations that are already socially and medically vulnerable. And that makes sense because these vulnerabilities are becoming more prevalent in The United States. For example, we live through multiple waves of the opioid epidemic since the nineteen nineties with the highest number of overdose deaths seen in 2022. We also continue to see major treatment gaps and workforce shortages in mental health care, which can leave serious psychiatric conditions untreated and poorly managed. And since 2017, around that time, we've seen a steady rise in housing insecurity and homelessness driven in part by affordable housing shortages and increasing rent burden.
Dhara Patel:And so the trends that we're seeing in our data are really reflecting the changes we're all experiencing in The US in housing, in behavioral health, and in access to resources that protect us from environmental exposure. And so I think the key messaging that we should have is that climate change affects everyone, but not equally. And cold related illnesses are rising not only because of weather instability, but because too many people lack the resources to protect themselves from it. And so I think we need to emphasize that our findings highlight how existing socioeconomic conditions here in The United States already determined who is most exposed and who ultimately gets sick.
Rob Lott:Good reminder to our listeners to check out Doctor. Patel's article on the May issue of Health Affairs and the numerous other research articles on the same topic in our theme issue on climate, health and equity. Doctor. Dara Patel, thank you so much for taking the time to chat with us. I had a lot of fun.
Dhara Patel:Thanks so much, Rob. This is great.
Rob Lott:To our listeners, thanks for tuning in. As I said, check out the whole theme issue at healthaffairs.org. If you enjoyed this episode, please leave a review, share it with a friend, and of course, tune in next week. Thanks, everyone. Thanks for listening.
Rob Lott:If you enjoyed today's episode, I hope you'll tell a friend about A Health Podyssey.