Significant increase of emergency department visits for heat-related emergency conditions in the United States from 2008 – 2019: a comprehensive nationwide study

Introduction Exposure to high temperatures is detrimental to human health. As climate change is expected to increase the frequency of extreme heat events, as well as raise ambient temperatures, an investigation into the burden of heat-related emergency department visits is necessary to assess the human health impact of this growing public health crisis. Methods Emergency department visits were sourced from the Healthcare Cost and Utilization Project Nationwide Emergency Department Sample. This dataset collects emergency department visit information from 989 facilities that represent a 20-percent stratified sample of United States hospital-owned emergency departments. Visits were included in this study if the medical diagnosis contained an ICD-9-CM or ICD-10-CM code specific to heat-related emergency conditions. Weighted heat-related emergency department visit counts were generated to estimate the total counts for heat-related emergency department visits across the United States. Visit year and month, hospital geographic region, patient age, and sex were recorded. Incidence rates per 100,000 US population, visit counts, and visit count percent change were analyzed on both a national scale and stratified by month, region, age, and sex. Results A total of 1,007,134 weighted heat-related emergency department visits between 2008 - 2019 were included in this study. The annual incidence rate per 100,000 US population increased by an average of 5.73% (95% CI: 8.64% – 20.1%) per year across the study period, rising from 20.56 in 2008 to 30.41 in 2019. For the twelve-year period, the burden of heat-related emergency department visits was greatest in the South (51.41%). Most cases occurred in July (29.56%), with visits increasing to the greatest degree in July (19.25%, 95% CI: 20.75% – 59.26%) and March (14.36%, 95% CI: 19.53% – 48.25%). Conclusions This study found a significant increase in emergency department visits for heat-related emergency conditions across the United States from the years 2008 to 2019. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement Efforts by Dr. Henry Xiang in this study were supported by a grant from the CDC National Center for Injury Prevention and Control (Grant #: 5R49CE003074-03; PI: Dr. Gary Smith). ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines and uploaded the relevant EQUATOR Network research reporting checklist(s) and other pertinent material as supplementary files, if applicable. Yes All data produced are available online from the Healthcare Cost and Utilization Project website.