Nationally, heat-related mortality rates have increased by nearly 17 percent annually since 2016. As a result, New York City now issues heat warnings and opens cooling centers when the heat index is predicted to reach 95 degrees Fahrenheit or higher for at least two consecutive days, or when the heat index is predicted to reach 100 degrees Fahrenheit or higher.
Older people, on the other hand, are known to be at higher risk of heatstroke and related mortality, have chronic heat-sensitive illnesses such as heart disease, kidney disease, and diabetes, and are more likely to take medications that impair heat regulation.
Researchers at New York University Grossman School of Medicine analyzed data from electronic medical records of patients 65 and older in two New York City emergency departments within the same health system to see who was most at risk from heat and at what temperatures. Researchers sought to determine whether patients presented to the emergency department with heat-related illnesses at temperature thresholds that differed from local government heat advisories.
Published in an online journal on March 20th JAMA network openResearchers found that in one ED that served a more climate-vulnerable population (patients from underserved minority racial and ethnic groups and with higher Medicaid dependence), patients were at risk for heat-related ED use starting at a maximum daily heat index of 66°F, with amplified risk observed between 90°F and 101°F. This amplified risk threshold of 90°F is lower than current municipal heat trigger thresholds. Advisory and related cooling programming. No significant association between heat and ED use among older adults was observed in ED facilities that serve more white, privately insured patients (a potentially climate-vulnerable population).
“With a severe heatwave already underway in the western United States, now is the time for health systems to prepare,” said Alexander Azan, MD, PhD, assistant professor in the Department of Population Health and senior author of the study.
Electronic health record data provided our team with the opportunity to identify heat exposure thresholds associated with emergency department (ED) use in vulnerable populations, but we found these to be distinct from population-level trends that inform municipal alert systems. ”
Alexander Azan, New York University Grossman School of Medicine
“In the health systems in this study, we found that ED use among vulnerable elderly patients spikes around 90°F rather than 95°F. Our hope is that other health systems will leverage their own electronic health record data to identify the heat thresholds at which patients are most at risk and target appropriate interventions,” Dr. Azan added.
Targeted deployment of heat safety measures tailored to the unique vulnerabilities of older adults can increase their ability to adapt to heat in a way that New York City’s current municipal practices, which rely on a 95°F threshold for initiation, do not take into account, Dr. Azan said.
How to conduct research
The researchers analyzed EHR data from patients aged 65 and older who visited two acute care hospitals in New York City, called ED-1 and ED-2, located 10 miles apart within the same health system. Researchers analyzed a total of 55,200 emergency department visits representing 15,092 unique patients in ED-1 and 19,559 unique patients in ED-2 during the 2022-2022 summer season (May to September). 2024. ED-1 works with community-based academic hospitals serving a socioeconomically, racially, and ethnically diverse patient population. ED-2 is housed in a larger academic medical center that serves a larger number of high-income patients. The proportion of patients enrolled in Medicaid in ED-1 was twice as high compared to ED-2.
The researchers matched each emergency room to temperature data from the LaGuardia Airport monitoring site. This data is highly correlated with other major New York City National Weather Service sites. We then calculated heat index values based on other heat indexes so that they could be directly compared to the New York City Heat Advisory thresholds.
In ED-1, the risk of heat-related ED use among older adults began to increase at 66°F, and increased risk was observed between 90°F and 101°F. Researchers observed no significant association in ED-2. The researchers roughly estimated that activation of the health system-based heat warning system on days with temperatures above 90°F when no heat advisories were issued could have prevented approximately 116 ED-1 visits during the study period.
“By leveraging EHR data, health systems can customize heat warning interventions to save lives and improve health during extreme heat events,” said co-investigator Leora I. Horwitz, MD, director of NYU Langone’s Center for Healthcare Innovation and Delivery Sciences.
Horwitz, who is also a professor in the Department of Population Health, says the research team next plans to combine identification of locally relevant exposure thresholds with a comprehensive assessment of how social and structural risk factors may further exacerbate the risk of heat-related ED use, and which health conditions in older adults have what effects. Such studies are expected to provide healthcare system-based customized heat warning strategies to reduce preventable heat-related ED use in older adults.
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New York University Grossman School of Medicine
Reference magazines:
Siau, E. et al. (2026) Extreme urban heat and emergency department visits among older adults. JAMA network open. DOI: 10.1001/jamanetworkopen.2026.2645. https://jamanetwork.com/journals/jamanetworkopen/fullarticle/2846734.
