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Am Fam Physician. 2005;72(5):951-952

The Centers for Disease Control and Prevention (CDC) has released updated statistics on the rates of hyperthermia and heat-related deaths. The report, “Heat-Related Mortality—Arizona, 1993–2002, and United States, 1979–2002,” was published in the July 1, 2005, issue of Morbidity and Mortality Weekly Report and is available online at

Continued exposure to ambient heat that is close to body temperature contributes to a significant number of deaths from hyperthermia, especially among older adults (i.e., 65 years or older). From 1979 to 2002, a total of 4,780 deaths were attributed to extreme heat in the United States. The incidence of such deaths was three to seven times greater in Arizona than in the United States overall from 1993 to 2002.

Older adults, children, and persons without access to air conditioning are at increased risk for heat-related illness and death. Persons with chronic mental disorders or cardiopulmonary disease, and persons taking medications that affect salt and water balance (e.g., diuretics, anticholinergics, tranquilizers that impair sweating) also are at greater risk.

Heat exhaustion is the most common form of heat-related illness. Signs of heat exhaustion include intense thirst, heavy sweating, weakness, paleness, anxiety, dizziness, fatigue, headache, nausea, and vomiting. Core body temperature may range from below normal to slightly elevated, and skin may be cool and moist. If left untreated, heat exhaustion can progress to heat stroke, a severe illness defined as a core body temperature of at least 40.6°C (105.1°F) accompanied by hot, dry skin and central nervous system abnormalities such as delirium, convulsions, and coma.

The CDC recommends that public health agencies in areas affected by extreme heat identify susceptible populations and risk behaviors, educate populations at risk, and design and implement location-specific heat response plans.

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