Heat-Related Deaths - Four States, July-August 2001, and United States, 1979-1999

Morbidity and Mortality Weekly Report. 2002;51(26) 

In This Article

Editorial Note

The cases summarized in this report demonstrate risk factors for heat-related illness. Heat-related illnesses include sunburn, heat cramps, heat rash, heat exhaustion, and heatstroke. Of these, the two most serious types of heat-related illness are heat exhaustion and heatstroke, both of which can result in death. Symptoms of heat exhaustion include heavy sweating, muscle cramps, fatigue, weakness, paleness, cold or clammy skin, dizziness, headache, nausea or vomiting, and fainting. Untreated heat exhaustion can progress to heatstroke [4]. Even with prompt medical care, 15% of heatstroke cases are fatal [5].

Symptoms of heatstroke include a high body temperature (oral temperature of ≥103º F [≥39.4º C] or a rectal temperature of 106º F [41.1º C]); red, hot, dry skin and no sweating; rapid pulse; throbbing headache; dizziness; nausea; confusion; disorientation; delirium; and coma. Heatstroke can occur in the absence of physical exertion. Infants, elderly persons, socially isolated persons, bedridden persons, and persons with certain mental and chronic illnesses are at highest risk [6,7]. The elderly, especially those aged ≥80 years, are susceptible to heat-related illness because they are less able to adjust to physiologic changes (e.g., vasodilation) that occur with exposure to excessive heat and are more likely to be taking medication for chronic illness (e.g., tranquilizers and anticholinergics) that increase the risk for heat-related illness [5]. Infants also are sensitive to heat. Conditions such as mild fever can progress quickly to heatstroke if heat stress occurs. Parents and other caregivers should provide adequate hydration during summer months and refrain from dressing children too warmly [5]. Adults also should keep well hydrated during summer months.

Heatstroke also can occur in young, healthy persons who are exercising [6], because physical exertion during hot weather increases the likelihood of fainting and cramps caused by increased blood flow to the extremities [5]. Onset of heatstroke can be rapid and is considered a medical emergency.

The findings in this report are subject to at least three limitations. First, information on decedents is provided by surrogates, who might not accurately describe characteristics or behavior of the decedents. Second, heat-related deaths due to weather conditions or exposure to excessive natural heat might represent only a portion of actual heat-related deaths. These deaths often are a diagnosis of exclusion and can be misclassified as a stroke or heart attack. Deaths attributed to cardiovascular and respiratory disease increase following heat waves [8]. In addition, jurisdictions might use different definitions of heat-related death. Finally, ICD-10 coding was introduced in 1999 and might not be comparable with previous data for 1979--1998.

To reduce morbidity and mortality from heat-related illness, many cities have developed emergency response plans. Local officials use meteorologic information and assess population characteristics to implement prevention strategies [7]. Spending time in an air-conditioned area is the strongest factor in preventing heat-related deaths [1,9]. The use of fans does not appear to be protective during periods of high heat and humidity [1]. If exposure to heat cannot be avoided, prevention measures should include reducing or eliminating strenuous activities or rescheduling them for cooler parts of the day; drinking water or nonalcoholic fluids frequently; taking cool showers frequently; wearing lightweight, light-colored, loose-fitting clothing; and avoiding direct sunshine [9].

Public health messages disseminated to all age groups can make the public aware of the signs and symptoms of heat-related illness. Prevention messages delivered as early as possible in the media can prevent heat-related illness, injury, and death [1].

Because many heat-related illnesses and deaths occur among the elderly population, older persons should be encouraged to take advantage of air-conditioned environments (e.g., shopping malls, senior centers, and public libraries) for part of the day. Parents and other caregivers should be educated about the heat sensitivity of children aged <5 years [5].

* The National Weather Service issues a heat advisory when the maximum daytime heat index is expected to be ≥105º F (40.6º C) and the minimum nighttime heat index is expected to be 80º F (26.7º C) for 2 or more consecutive days. The heat index takes into account air temperature and relative humidity and indicates the actual feel of the temperature to the body.

† Underlying cause of death during 1979--1998 is classified according to the International Classification of Disease, Ninth Revision (ICD-9). Excessive heat has three categories: E900.0 "due to weather conditions," E900.1 "of man-made origins," and E900.9 "of unspecified origin." The data for 1999 are from ICD-10; code X30 "exposure to excessive natural heat" was added to the 1979--1998 ICD-9 code E900.0, "excessive heat due to weather conditions."

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