Extreme heat is associated with a significant increase in emergency room visits for a wide range of ailments, including accidental gunshot wounds, kidney problems, skin conditions, and even marijuana-related mental health issues, according to a comprehensive study of Chicago hospital records. The research, which analyzed over 900,000 emergency room and urgent care visits from 2011 to 2023, identified more than a dozen categories of illnesses and injuries that become more frequent when temperatures reach 92.6 degrees Fahrenheit (33.7 degrees Celsius) or higher.
While the study focused on Chicago, its findings highlight broader, often underestimated health risks and rising healthcare costs linked to rising global temperatures. Researchers from Northwestern University examined hospital and urgent care data, looking for trends beyond traditional heat-related illnesses like heat stroke.
The study found that some conditions saw dramatic increases during hot spells. Accidental gunshot wounds, for instance, were found to be more than 30 times more frequent on hot days compared to cooler periods. Injuries from assault also showed a notable increase. The research noted that the association between high temperatures and these medical issues does not definitively prove causation but provides strong correlational evidence.
"Heat-related illness is undercounted when studies only search for explicit heat codes like heat stroke," said Dr. Nicholas Cozzi, president-elect of the Illinois College of Emergency Physicians, who was not involved in the study. "This study helps confirm that we've been underestimating health risks from heat exposures."
Kidney and renal system issues were among the most frequently observed conditions with an uptick during hot weather. Skin problems, while known to doctors, are less commonly discussed in relation to heat in public discourse. The study also found a link between high temperatures and exacerbations of drug effects, specifically noting mental health issues associated with marijuana use. Researchers suggest that when the body is under physiological stress from heat, certain substances may have more pronounced effects.
Conversely, cardiovascular problems, often linked to heat in other research, did not show a significant spike in this particular study. Researchers theorize this may be because patients experiencing cardiovascular issues often have co-occurring conditions, such as kidney or fluid imbalances, which influence how their medical records are coded. These underlying issues might mask the direct heat impact on the cardiovascular system in the data.
Co-author Daniel Horton, a climate scientist at Northwestern, emphasized the growing intensity and frequency of heat waves, stating, "So a study like this indicates that those heat waves have real effects on people, not only on the likelihood of mortality, but of morbidity as well."
Experts suggest that the findings underscore the need for greater public awareness. Dr. Abel Kho, the study's senior author and a professor at Northwestern University's medical school, advised that individuals with chronic conditions, such as kidney disease, multiple sclerosis, or venous issues, should treat extreme heat days as triggers for extra caution, rather than solely viewing them as days for limiting outdoor activities.