Metro Phoenix heat is no joke, even in what the rest of the country might call spring time. The danger of heat-induced catastrophic incidents is well-documented — from heatstroke to wildfires.
Eun Young Choi, a postdoctoral researcher at the University of Southern California, wanted to study the longer-term effects of heat on the human body. What exactly does it do to a person to spend as much time as we Valley residents do living in extreme temperatures?
In a recent study, Choi and her team looked at the ways that extreme heat affects people on a cellular level. Choi joined The Show to talk about what they found.
Full conversation
EUN YOUNG CHOI: We thought that this is an important gap in the literature, because the physical toll of heat might not show up right away as a diagnosable health condition. But they could be taking a silent toll at the molecular or the cellular level in our body.
SAM DINGMAN: So tell us what the results of your study suggest about that. What is happening to our cells when we spend extended periods of time in extreme heat?
CHOI: So yeah, our study essentially finds a significant association between neighborhoods with more days of extreme heat and older biological age — comparable to the effects with smoking and heavy alcohol consumption, the two well-established risk factors for accelerating aging. So, for example, we found that residents in places where extreme heat events happening for near half of the year, such as Phoenix, experienced up to 14 months of additional biological aging compared to those living in much cooler areas with fewer than 10 heat days per year, such as in Seattle.
What's important is that this association that we find remained even after controlling for a lot of other individual and community level differences, such as income, education, race, ethnicity, physical activity, smoking and alcohol use. All factors that could otherwise explain differences in aging.
DINGMAN: Wow, so it really is, it's the heat that is aging the cells more quickly. Can you talk a little bit about what the downstream effects on someone's physiology on their health might be as a result of having their cells age faster? Like what could that lead to?
CHOI: There is a growing body of literature suggesting that this acceleration can lead to development of chronic conditions such as cardiovascular disease, or even early death.
DINGMAN: Obviously what you're describing for a lot of folks listening to this could conceivably be a little terrifying. Just this idea that by virtue of living in a place like Phoenix, where it is extraordinarily hot, without doing anything else, potentially, that could be bad for your health, you're just existing somewhere where it's, it's making your body age faster. Are there steps that eventually people living in environments like Phoenix could one day take that would counteract this at all?
CHOI: Mhm. Yeah, so, there are two points that I really want to mention regarding your question. First, our study suggests that it's chronic heat exposure, not the, like, just several months of exposure. So, one definite way to prevent this adverse health impact is definitely prevent repeated exposure that is happening to people.
But also, second thing is our city really looks at the overall local level exposure, so that our findings don't really mean that every person living in Phoenix has an older biological age. But rather it's just average. And there are many factors at play and some individuals may be more resilient or have ways to reduce their heat exposure, and that's definitely the area where more research is needed. But we can't just tell people, “pack up and move to somewhere cooler,” right?
So that's really why we need to be thinking about age-appropriate mediation strategy. We really think that we can't just focus on individual solutions. We need to think about how we design our neighborhoods more heat resilient. So, even simple changes to neighborhood design can make a big impact, like adding shade to bus stops. So that older adults can sit down with shade. Like, simple interventions like these can be life-saving for especially vulnerable populations, like older adults.
DINGMAN: Yeah, well, so obviously you, you've just published this study that has these really remarkable findings about the effects on epigenetic aging of chronic heat exposure, and I know you're actually planning to move here to Phoenix later this year, presumably to continue this research. What do you feel is the next step?
CHOI: One of our biggest priorities is understanding why some people are more affected than others. Right now, we've looked at shorter time frames, but we need to really understand the long-term effects — that's heat exposure from early life, for example, even accelerate aging over decades. Are there any critical windows? Does the damage build up over time? Like, more importantly, I think that I want to focus on some — why all this like answering scientific question, I want to do more community engaged work so that, like, raise the awareness among nursing home residents. So that we can work together to educate people and empower people.
DINGMAN: Yeah. Well, in the meantime, if somebody is listening to this and they're thinking, “Oh, my God, like what do I do? Summer is coming.” I mean, we know that things like stress are bad for our bodies — smoking, lack of sleep, excessive alcohol consumption, these sorts of things. Does your research so far suggest that those things are extra dangerous when one lives in chronic heat?
CHOI: So, our study didn't explore that, but we know a lot from other environmental-exposure literature — like air pollution — that if you're living in really highly polluted areas, and if you feel a lot of stress. From, like, highly disadvantaged neighborhoods, or like bad health behaviors, then those are the most vulnerable population. So, in addition to this well-known risk factor, if you also live in a very hot area, there are potentially this compounding impacts on your body.
