In this analysis, the inclusion of hyperthermia as a contributing cause of death increased by 54% the total number of heat-related deaths during 1999–2003 that would have been counted through inclusion of a heat-related underlying cause alone. Because heat-related illnesses can exacerbate existing medical conditions and death from heat exposure can be preceded by various symptoms, heat-related deaths can be difficult to identify when illness onset or death is not witnessed by a clinician. In addition, the criteria used to determine heat-related causes of death vary among states. This can lead to underreporting heat-related deaths or to reporting heat as a factor contributing to death rather than the underlying cause (3). The demographics (e.g., sex, age group, and state) of the decedents described in this report are consistent with previous descriptions of persons at risk for heat-related deaths (4,5).
This analysis also provides additional information on the underlying causes of death in which hyperthermia was a contributing factor. Although this report might still underestimate the extent of overall heat-related morbidity and mortality, the inclusion of hyperthermia as a contributing factor to death provides a more comprehensive view of the actual effects of heat-related illnesses. The association between cardiovascular disease and heat-related death is well established (7); this analysis suggests the need for additional investigations of the association between noncardiovascular conditions, such as endocrine and respiratory diseases, and the risk for heat-related death.
Continued exposure to excessive heat can lead to hyperthermia or death. Of the heat-related illnesses, heat exhaustion and heatstroke are the most serious. Heat exhaustion is characterized by muscle cramps, fatigue, headache, nausea or vomiting, and dizziness or fainting. The skin is often cool and moist, indicating that the body’s mechanism for cooling itself (i.e., sweating) is still functioning. The pulse rate is typically fast and weak, and breathing is rapid and shallow. If untreated, heat exhaustion can progress to heatstroke (1). Heatstroke is a serious, life-threatening condition characterized by a high body temperature (>103ºF [>39.4ºC]); red, hot, and dry skin (no sweating); rapid, strong pulse; throbbing headache; dizziness; nausea; confusion; and unconsciousness. Symptoms can progress to encephalopathy, liver and kidney failure, coagulopathy, and multiple organ system dysfunction (2). Prompt treatment of heat-related illnesses with aggressive fluid replacement and cooling of core body temperature is critical to reducing morbidity and mortality (2).
Many heat-related deaths, regardless of whether they are associated with chronic medical conditions, are preventable. During periods of extreme heat, heat-related illnesses can be prevented by avoiding strenuous outdoor activities, drinking adequate amounts of fluid, avoiding alcohol consumption, wearing lightweight clothing, and using air-conditioning. Groups at high risk include young children, persons aged >65 years, persons who do strenuous activities outdoors, and persons with chronic (particularly cardiovascular) medical conditions (8).
During heat waves, young children, older adults, and chronically ill persons should be checked frequently by relatives, neighbors, and caretakers to evaluate their heat exposure, recognize symptoms of heat-related illness, and take appropriate preventive action. Regardless of the outdoor temperature, parents and other child-care providers should never leave children alone in cars and should ensure that children cannot lock themselves inside enclosed spaces, such as the trunks of automobiles.
Communities can prepare for heat-related illnesses by creating well-defined heat response plans (HRPs) (9). Both governmental and nongovernmental organizations, each with specific roles and responsibilities, can be involved in this planning. HRP protocols and communication tools should be reviewed annually, before the summer months begin. The HRPs should identify populations at high risk for heat-related illness and death and determine which strategies will be used to reach them during heat emergencies. The HRP should also include specific criteria for activation and deactivation of the plan. Postemergency evaluations of HRPs are necessary to make appropriate revisions and improve plan effectiveness.
References
- CDC. Extreme heat. Atlanta, GA: US Department of Health and Human Services, CDC; 1996. Available at http://www.cdc.gov/nceh/hsb/extremeheat.
- Lugo-Amador NM, Rothenhaus T, Moyer P. Heat-related illness. Emerg Med Clin North Am 2004;22:315–27.
- Donoghue ER, Graham MA, Jentzen JM, Lifschultz BD, Luke JL, Mirchandani HG. Criteria for the diagnosis of heat-related deaths: National Association of Medical Examiners: position paper. Am J Forensic Med Pathol 1997;18:11–4.
- CDC. Heat-related mortality—Arizona, 1993–2002, and United States, 1979–2002. MMWR 2005;54:628–30.
- CDC. Heat-related deaths—Chicago, Illinois, 1996–2001, and United States, 1979–1999. MMWR 2003;52:610–3.
- CDC. Multiple-cause-of-death mortality data sets, 1999–2003. Hyattsville, MD: US Department of Health and Human Services, National Center for Health Statistics.
- Wainwright SH, Buchanan SD, Mainzer HM, Parrish RG, Sinks TH. Cardiovascular mortality—the hidden peril of heat waves. Prehospital Disaster Med 2000;15:79.
- Semenza JC, Rubin CH, Falter KH, et al. Risk factors for heat-related mortality during the July 1995 heat wave in Chicago. N Engl J Med 1996;35:84–90.
- Bernard SM, McGeehin MA. Municipal heat wave response plans. Am J Public Health 2004;94:1520–2.
