Extreme heat may be associated with far more health problems than the conditions commonly linked to high temperatures, including skin disorders, kidney failure, multiple sclerosis flare-ups and some forms of physical trauma, according to a new study.
Researchers found links between intense heat and more than 30 diagnoses that are often overlooked when assessing the health effects of extreme temperatures. The findings come as Europe experiences repeated heatwaves and record temperatures, increasing pressure on hospitals and emergency services.
Heat exhaustion, heatstroke and dehydration are among the best-known consequences of prolonged exposure to high temperatures. However, the study suggests the wider health burden could be considerably larger.
Published in Science Advances, the research examined 1,803 diagnoses recorded during almost one million emergency department and urgent care visits in Chicago between May and September from 2011 to 2023.
Researchers identified several conditions that became more common during periods of extreme heat. These included skin rashes and swelling, acute kidney failure, multiple sclerosis, mental and behavioural disorders, as well as insect bites and stings.
The researchers also found an association between extreme temperatures and a range of injuries, including accidental and violent trauma. A total of 23 injury, poisoning or external-cause diagnoses met the study’s criteria for being heat-related.
Hyojung Jang of Northwestern University, who led the study, said focusing only on familiar heat-related illnesses could lead authorities to underestimate the overall health impact of rising temperatures.
“If we’re only tracking the more commonly known heat-related illnesses, we’ll underestimate the true heat-related health burden,” Jang said.
The researchers said extreme heat can place significant stress on both the body and mind. Daniel Horton, an associate professor at Northwestern and co-author of the study, said previous research had found that extreme temperatures could contribute to more aggressive behaviour.
Heat can also increase the risk of accidents by affecting concentration and putting additional strain on the body.
Urban areas face an additional challenge from the urban heat island effect, in which buildings and paved surfaces absorb and retain heat, causing cities to remain warmer than surrounding areas.
The study’s findings could help healthcare providers prepare for increased demand during heatwaves. Researchers suggested expanding clinical alerts to include kidney and fluid-balance problems, some of which may develop several days after heat exposure.
Better monitoring could help emergency departments anticipate increases in patients suffering from dehydration and kidney-related complications during and after extreme heat events.
The researchers stressed that their findings are based on data from Chicago and need to be tested in other regions, climates and healthcare systems.
As extreme heat becomes more frequent in many parts of the world, the study suggests that preparing for its health effects will require attention to a much broader range of illnesses than those traditionally associated with heat.
