Heat-Related Deaths -- United States, 1993

From July 1 through July 13, 1993, the heat wave in the eastern United States has been implicated as the direct cause of or a contributing factor to 84 deaths among persons residing in the Philadelphia area. In Philadelphia County, the medical examiner (ME) lists hyperthermia as a contributing factor leading to death if a decedent is elderly or infirm and was exposed to a hot environment. However, reporting of hyperthermia on a death certificate depends on the criteria of individual MEs or coroners. This article describes three case reports of heat-related deaths in other parts of the United States in 1993, summarizes risk factors for this problem, and reviews measures to prevent heat-related illness.

Case 1. On June 2, a 1-year-old infant was left sleeping for approximately 75 minutes in the back seat of an automobile with the windows closed. The child died from hyperthermia attributable to exposure to a hot environment.

Case 2. On July 7, a 48-year-old woman was found unconscious at her kitchen table in her mobile home and was pronounced dead on arrival at a local emergency department. Rectal temperature, measured at the emergency department, was 108 F (42 C) following a 20-minute ride in an air-conditioned ambulance. At the time the decedent was discovered, all the windows in her home were closed and all fans were turned off. The room temperature was approximately 120 F (48.8 C). She had been dehydrated the previous day when she presented to a local health department for a prescheduled visit. The direct cause of death was hyperthermia.

Case 3. On July 8, a 68-year-old man was found in a slightly decomposed state in his apartment. He was last seen alive on July 5. Room temperature exceeded 100 F (38 C). Although the direct cause of death was atherosclerotic heart disease, hyperthermia was considered a contributing factor.

Reported by: H Merchandani, MD, P Pace, Office of the Philadelphia County Medical Examiner, Philadelphia. AZ Hameli, MD, R Pressler, JG Tobin, MD, Office of the Chief Medical Examiner, State of Delaware. JH Davis, MD, V Melton, Office of the Chief Medical Examiner, District 11 (Dade County), Florida. Surveillance and Programs Br, and Health Studies Br, Div of Environmental Hazards and Health Effects, National Center for Environmental Health, CDC.

Editorial Note

Editorial Note: During 1979-1988, 4523 * deaths in the United States were attributed to excessive heat exposure, and in 1980 (a year with a severe heat wave), 1700 heat-related deaths were reported **. Mortality from all causes increases during heat waves, and excessive heat is an important contributing factor to deaths from other causes, particularly among the elderly (1). However, because deaths attributable to heat-related illness vary according to criteria used by individual MEs and coroners, a standard definition is needed to accurately assess these deaths. The current heat wave in the eastern part of the United States underscores the need for health-care providers, public health agencies, and the public to recognize risk factors for heat-related illness and to implement measures to lower the risk for these illnesses.

Based on data for the United States for 1979-1988, the risk for death from excessive exposure to heat varied by age, sex, and race (Figure 1). This risk was higher among men and non-Hispanic blacks, although these rates were not adjusted for potential risk factors, such as socioeconomic status (2). Regardless of sex or race, persons aged greater than or equal to 65 years were more susceptible to the adverse effects of heat than were younger persons, and heat-related death rates increased with age: the risk of heat-related mortality for persons aged greater than or equal to 85 years was 3.6 times that for persons aged 65-74 years.

Persons at greatest risk for heat-related illness include the very young, the elderly, and those who overexert themselves in hot environments, either at work or during recreational activities. However, any person is at risk for fatal heatstroke if sufficiently exposed. Because young children (particularly infants), the elderly, and the immobile may be unable to obtain adequate fluids or to avoid hot environments, they are at greater risk for heat exhaustion or heatstroke (3). The use of certain drugs, such as neuroleptics or medications with anticholinergic effects, may also increase the risk for heat-related illness (3). Healthy adults who are unacclimatized to the heat and who work or exercise vigorously outdoors, who fail to rest frequently, or who do not drink enough fluids are also at high risk. Excessive alcohol consumption may cause dehydration and result in heat-related illness (3).

Heatstroke, the most serious heat-related illness, is a medical emergency. It is characterized by a body temperature greater than or equal to 105 F (40.5 C) and may include disorientation, delirium, and coma. Onset of heatstroke can be rapid: clinical status can change from apparently normal to seriously ill within minutes. Treatment of heatstroke involves the rapid lowering of body temperature (e.g., ice bath) (3). Heat exhaustion -- a milder form of heat-related illness that may develop after several days of high temperatures and inadequate or unbalanced replacement of fluids and electrolytes -- is characterized by dizziness, weakness, and fatigue and may require hospitalization.

The most effective measures for preventing heat-related illness include reducing physical activity, drinking additional liquids, and increasing the amount of time spent in an air-conditioned environment (3). Physically active persons can reduce risk for heat-related illness by scheduling exercise during the cooler parts of the day and by drinking additional nonalcoholic fluids.

The use of air conditioning will reduce the risk for heatstroke, even if it is available only for part of the day. The elderly should be encouraged and assisted in taking advantage of such environments in private or in public places (e.g., shopping malls, public libraries, and heat-wave shelters).

Salt tablets are not recommended and may be potentially dangerous for most persons (2). Persons for whom fluid restriction has been prescribed or who are taking diuretic medications should alter their fluid intake patterns only if advised by their physicians. Although the use of fans may increase comfort at low temperatures, fans are not protective against heatstroke at dangerously high temperatures. Fan distribution, as part of heat-wave relief, is not recommended (4,5), and persons without home air conditioners should seek shelter in an air-conditioned environment (3).

References

1. Ellis FP. Mortality from heat illness and heat-aggravated illness in the United States. Environ Res 1972;5:1-58.

2. Jones TS, Liang AP, Kilbourne EM, et al. Morbidity and mortality associated with the July 1980 heat wave in St. Louis and Kansas City, Missouri. JAMA 1982;247:3327-31.

3. Kilbourne EM, Choi K, Jones TS, Thacker SB, and the Field Investigation Team. Risk factors for heatstroke: a case-control study. JAMA 1982;247:3332-6.

4. Lee DHK. Seventy-five years of searching for a heat index. Environ Res 1980;22:331-56.

5. Steadman RG. A universal scale of apparent temperature. J Clim App Meteorol 1984;23:1674-87.

* Underlying cause of death attributed to excessive heat exposure and coded E-900 according to the International Classification of Diseases, Ninth Revision. 

** These data were obtained from the Compressed Mortality File (CMF), provided by CDC's National Center for Health Statistics. It contains information from death certificates filed in the 50 states and the District of Columbia that have been prepared in accordance with external cause codes from the International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM). CDC's Wide-ranging ONline Data for Epidemiologic Research (WONDER) computerized information system was used to access CMF data.

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