Scientists Identify Dozens of Overlooked Health Risks During Heatwaves

Extreme heat can trigger far more health problems than overheating and dehydration. A new study has identified an association between high temperatures and more than 30 diagnoses, ranging from acute kidney failure and multiple sclerosis flare-ups to skin rashes and injuries.

This summer, Europe experienced some of its most extreme temperatures on record. During several consecutive heatwaves, thermometers repeatedly registered record highs, Euronews reports.

The scorching weather resulted in thousands of excess deaths, pushed healthcare systems to their limits, and highlighted the urgent need to improve preparedness for such periods in the future.

Extreme temperatures pose a serious health risk. The most widely recognized consequences include overheating, heatstroke, and dehydration.

However, researchers identified more than 30 diagnoses whose incidence increased significantly during periods of extreme heat.

The study, published in Science Advances, found a strong association between heat and less widely recognized health problems, including multiple sclerosis flare-ups, skin rashes, and various types of injuries.

“It is a responsibility of the public health system to protect the people and communities that are most vulnerable to the harmful effects of climate change,” said study author Hyojeong Kim of Northwestern University in the United States.

“If we only track the most well-known heat-related illnesses, we will underestimate the true health burden associated with heat. As a result, vulnerable people and communities may simply be overlooked,” she added.

For the study, researchers analyzed 1,803 diagnoses recorded during nearly one million visits to emergency departments and urgent care clinics in Chicago between May and September from 2011 to 2023.

The researchers found that heat was associated with diagnoses including skin rashes and swelling, acute kidney failure, multiple sclerosis, mental and behavioral disorders, as well as insect bites and stings — conditions that can often receive less attention in emergency care settings.

The authors noted that risks can be particularly high in cities because of the so-called “urban heat island” effect. In metropolitan areas, temperatures can be several degrees higher than in surrounding regions, while heatwaves may also last longer.

The findings also suggest that extreme heat may be associated with an increase in accidental and violent injuries, including assaults and incidents involving firearms. The researchers identified 23 types of injuries, poisonings, and other external causes that met their criteria for a “heat-associated” diagnosis.

“Previous research has shown that people are often more aggressive when exposed to extreme heat, and that likely plays a role here as well,” said study co-author Daniel Horton, an associate professor at Northwestern University.

“When it’s hot outside, the body is under stress, and the mind is under stress as well. That can lead to distraction and irritability and may result in more accidents,” he added.

According to the authors, the findings could help healthcare systems better prepare for future periods of extreme heat.

This could include updating clinical alerts to cover a broader range of conditions, particularly kidney and fluid-electrolyte disorders, which may not become apparent until several days after heat exposure.

By taking these potential diagnoses into account, emergency departments and urgent medical services could better anticipate and prepare for increases in visits related to dehydration and kidney problems during and immediately after periods of extreme heat.

The authors emphasize that the findings are currently based only on data from Chicago. Further research is therefore needed to determine whether the same patterns occur in other populations, climates, and healthcare systems.