Extreme heat: Who is most vulnerable?

Last year, extreme heat killed 2,325 people in the United States, a 117% increase in such deaths since 1999, according to an August study published in the Journal of the American Medical Association.

While people often think of daytime heat as being particularly dangerous, high overnight temperatures can be even more so, said Duke University’s Ashley Ward at the Council for the Advancement of Science Writing’s New Horizons in Science briefings at the ScienceWriters2024 conference Nov. 9 in Raleigh, N.C.

Ward, director of Duke’s Heat Policy Innovation Hub, told the audience of science writers that finding solutions to the health effects of rising heat, such as setting a national temperature standard, requires listening to the people who are the most vulnerable.            

Ward discussed a study her team conducted on the effects of heat on preterm births—before 37 weeks gestation—in the Piedmont and eastern regions of North Carolina. When overnight temperatures reached 75 degrees, there was a 4% increase in preterm births compared to nights with lower temperatures. At 80 degrees overnight, it was 7%. “That’s not small anymore,” Ward said.

It’s not just pregnant women that are at risk from extreme heat. “The number one risk group in North Carolina is men, ages 15 to 45, and they don’t live in cities,” Ward said. “The solutions that we developed for heat, tree-planting campaigns, cool pavement, cooling centers, these things don’t transfer easily to a rural environment.”      

Ward’s interest in extreme heat began when she worked for a National Oceanic and Atmospheric Administration (NOAA) program in rural North Carolina more than a decade ago. Some residents told her that they rationed their energy use, like turning off air conditioning or fans, during the summer so they could afford to buy food.

“We have people that are creating ovens out of their homes so they can buy their insulin, and they’re having to make that kind of choice, which is just awful,” she said.

 For some, like students and prisoners, the choice is out of their hands. Roughly 40 percent of public schools in the United States don’t have adequate HVAC systems. “In the middle of the summer, we see learning outcomes impacted,” Ward said, “primarily in math and science and particularly among female students.”   

In prison, extreme heat can be deadly—especially without the reprieve of cooler overnight temperatures.  “Every year you hear about some extraordinary cases where prisoners literally cook to death in their cell,” Ward said. “This is a human rights issue.”