How electronic health records could refine hospitals’ heatwave strategies

When a heat wave strikes, its exact impact on patients isn’t always clear until months later, when insurance claims data becomes available.

But a study from Harvard University, Boston University, and health data and analytics company Truveta, published Aug. 31 in the journal Nature Health, shows data can be obtained much faster. In this study, researchers were able to access emergency department (ED) visit data within electronic health record (EHR) data just one week after a visit happened.

This means health systems and public health officials can, in theory, use EHR data to assess in near real time whether measures like cooling centers or outreach are working, Amruta Nori-Sarma, the study’s lead author and deputy director of the Center for Climate, Health, and the Global Environment at Harvard T.H. Chan School of Public Health, told Healthcare Brew.

The study also provided additional findings about heat’s health impacts. During the June 2025 heat wave, 9.2% of all-cause ED visits were attributable to heat, according to EHR data across 19 states from hospitals in the Truveta network. During the August 2025 heat wave, 8.3% were attributable to heat. These results echoed other studies that logged more ED visits during hotter weather. Illnesses like kidney disease and psychiatric conditions saw especially high spikes.

We talked with Nori-Sarma to learn more about this study and the potential she sees in using EHR data to inform responses during heat waves.

This interview has been lightly edited for length and clarity.

What part of the study’s findings were most interesting to you?

A lot of times, high-quality data aren’t available in real time after an extreme weather event occurs. So this was kind of a proof of concept.

[It] provides us with an opportunity to potentially understand, if we know the heat wave is coming, could we help prepare collaborators in different clinical settings to handle the surge in emergency department visits? And then could we use data like these to potentially evaluate the effectiveness of those types of interventions?

I think that’s the next stage. But this early work was a demonstration of the viability of leveraging these data to understand the health impacts of heat exposure. There’s been a long-standing hypothesis that people are more likely to get diagnosed with heat-related illnesses because it’s hot outside. We saw in our data that, in fact, there was a rapid increase in the rates of emergency department visits for heat-related illnesses during hotter periods last summer. But we see these other types of outcomes, including kidney diseases, including mental health ED visits, that accelerate a little bit more slowly as temperatures increase, and then you see the signal during the heat wave periods…So maybe if we look beyond heat-related illnesses to other types of health endpoints, we might find information that we could use to prepare. We’re starting to see these [heat waves] creep up, so we need to prepare for the surge in the need for care.

What would preparations for a heat wave look like?

If you’re worried about patients with kidney disease who are reliant on dialysis, for example, you might want to make sure that they have good access to dialysis care, especially during extreme heat waves.

It might also be that you know that there’s a patient who is particularly vulnerable, and having advanced information about an upcoming event leads to some sort of clinician-to-patient outreach. Maybe you want to get in touch with your patient that you know has a chronic mental health condition to say, “Do you have access to your medications? Do you have access to the types of behavioral health services that you would need?”

How can non-professionals help?

One of the best protections that we have is friends checking in on friends, neighbors making sure that your neighbors are safe. If you have a loved one that you know is particularly vulnerable or sensitive to heat, make sure that they have access to whatever they need to stay safe. We’re going to continue to see heat waves that are more frequent, more intense, lasting for longer, so these social networks become even more important in those contexts.