What Is More Deadly in the U.S.: Hot Weather or Cold?

THURSDAY, Aug. 27, 2020 (HealthDay News) -- Extreme weather days have been on the rise worldwide since the advent of global warming. But a new U.S. study finds that cold weather is responsible for most temperature-related deaths in Illinois.

Researchers analyzed data on heat- and cold-related injuries that required a hospital visit in the state between 2011 and 2018. They identified around 24,000 cases each related to the cold and to heat.

Of those, there were 1,935 cold-related deaths and 70 heat-related ones. The cold caused 94% of temperature-related deaths, even though hypothermia (a drop in the body's core temperature) was responsible for only 27% of temperature-related hospital visits.

The University of Illinois Chicago study was recently published in the journal Environmental Research.

"With the decrease in the number of cold weather days over the last several decades, we still see more deaths due to cold weather as opposed to hot weather," said study author Lee Friedman, an associate professor of environmental and occupational health sciences.

He said this is partly due to the body's poorer ability to regulate its temperature once hypothermia sets in. But fewer cold weather days overall also contributes because people don't have time to acclimate when those rarer cold days do occur, Friedman said.

Even mildly cool temperatures can trigger hypothermia, which is a drop in body temperature from the normal 98.7 degrees to 95 degrees Fahrenheit.

When people develop hypothermia, their organs and systems begin to shut down in an effort to preserve the brain. Once started, this process can be difficult to get under control.

People who are more regularly exposed to lower temperatures are better able to resist hypothermia, as was shown in this study.

"People who were experiencing homelessness in the records we looked at were less likely to die from temperature-related injury," Friedman said in a university news release. "Because they have greater outdoor exposure, they acclimate better to both heat and cold."

In general, people are better able to avoid heat-related issues by going to a cooler place or by hydrating, Friedman said.

"Currently, the public health community focuses almost exclusively on heat injury. Our data demonstrate that improved awareness and education are needed around the risk for cold injuries, especially since there are fewer but more severe cold weather days -- leaving less chance for acclimation, which can be protective against hypothermia," he concluded.

The researchers said the study shows how public health messages regarding weather must be tailored to different climate zones in the United States.

More information

The U.S. Centers for Disease Control and Prevention has more on hypothermia.