Summertime acute heat illness in U.S. emergency departments from 2006 through 2010: analysis of a nationally representative sample

Abstract

Background: Patients with acute heat illness present primarily to emergency departments (EDs), yet little is known regarding these visits.

Objective: We aimed to describe acute heat illness visits to U.S. EDs from 2006 through 2010 and identify factors associated with hospital admission or with death in the ED.

Methods: We extracted ED case-level data from the Nationwide Emergency Department Sample (NEDS) for 2006-2010, defining cases as ED visits from May through September with any heat illness diagnosis (ICD-9-CM 992.0-992.9). We correlated visit rates and temperature anomalies, analyzed demographics and ED disposition, identified risk factors for adverse outcomes, and examined ED case fatality rates (CFR).

Results: There were 326,497 (95% CI: 308,372, 344,658) cases, with 287,875 (88.2%) treated and released, 38,392 (11.8%) admitted, and 230 (0.07%) died in the ED. Heat illness diagnoses were first-listed in 68%. 74.7% had heat exhaustion, 5.4% heat stroke. Visit rates were highly correlated with annual temperature anomalies (Pearson correlation coefficient 0.882, p = 0.005). Treat-and-release rates were highest for younger adults (26.2/100,000/year), whereas hospitalization and death-in-the-ED rates were highest for older adults (6.7 and 0.03/100,000/year, respectively); all rates were highest in rural areas. Heat stroke had an ED CFR of 99.4/10,000 (95% CI: 78.7, 120.1) visits and was diagnosed in 77.0% of deaths. Adjusted odds of hospital admission or death in the ED were higher among elders, males, urban and low-income residents, and those with chronic conditions.

Conclusions: Heat illness presented to the ED frequently, with highest rates in rural areas. Case definitions should include all diagnoses. Visit rates were correlated with temperature anomalies. Heat stroke had a high ED CFR. Males, elders, and the chronically ill were at greatest risk of admission or death in the ED. Chronic disease burden exponentially increased this risk.

Figure 1

Annual population-based rates of ED visits for heat illness by average annual temperature anomalies for NEDS states. A trendline with 95% CI is included for reference. The Pearson correlation coefficient is 0.882, p = 0.005.

Figure 2

Adjusted odds ratios of hospital admission or death in the ED for different degrees of chronic disease burden, stratified by all ED visits, all acute heat illness, and only heat stroke visit (ICD-9-CM code 992.0). The index was calculated based on combining the CCS and CCI information provided in HCUP.