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Current Trends Hypothermia -- United States

In 1979,* excessive cold was reported as the underlying cause of 711 deaths among persons of all ages and races and both sexes (Table 1).

Deaths of males from excessive cold exceeded those of females (2.8:1 for all ages), especially in the 30- to 44-year age group (7.8:1). Persons in the 65- to 74-year category, representing 7% of the total U.S. population (1), accounted for 18% of these deaths. Persons 75 years and older, representing 4% of the U.S. population (1), accounted for 28%. Data for the last few years indicate the hypothermia death rate among the elderly may be increasing (2).

Hypothermia, defined as a core body temperature lower than 35 C (95 F), may be classified as acute, subacute, or chronic. Acute hypothermia is caused by a rapid loss of body heat, usually from immersion in cold water. Subacute hypothermia often occurs from exposure to cool weather (below 10 C (50 F)) outdoors, in combination with wind chill, wet or inadequate clothing, fatigue, and/or inadequate nutrition. Chronic hypothermia in predisposed persons generally occurs from exposure to cold temperatures (below 16 C (60 F)) indoors over a prolonged period. Predisposed persons have an impaired perception of cold; decreased mobility; and inadequate nutrition, clothing, and heating systems. This group typically includes the poor, the elderly, and drug or alcohol abusers. *The latest year for which data are available for the entire United States.

Early signs include nonspecific disturbances of mental activity and judgment, which may be mistaken for other conditions and thus delay corrective measures (Table 2). Severe and life-threatening hypothermia occur when core body temperature falls below 30-32 C (85-90 F). Diagnosing the condition, therefore, requires recognizing early signs and symptoms and accurately measuring core body temperature with low-reading thermometers (below 35 C (95 F)). Treating patients with severe hypothermia consists of carefully rewarming them and monitoring their temperatures (3,4). All hypothermic patients--including those showing no signs of life--should be transported quickly and carefully to a medical facility. When appropriate, rescuers should start cardiopulmonary resuscitation. Very cold patients, if moved excessively, are susceptible to ventricular arrhythmias (4). Reported by Special Studies Br, Chronic Diseases Div, Program Svcs Br, Environmental Health Svcs Div, Center for Environmental Health, CDC.

Editorial Note

Editorial Note: Hypothermic mortality is probably underreported for four reasons: 1) its physical signs may not be recognized because they resemble other conditions; 2) hospitals may not use low-temperature thermometers; 3) medical personnel may be unaware of hypothermia's significance; and 4) even an autopsy cannot prove hypothermia as an underlying cause of death. Further study and better reporting are needed to explain the age and sex differences in the hypothermic death rates noted in Table 1 and to make such study valid.

Preventing hypothermia involves knowing of the condition and its risk factors and taking necessary precautions to avoid excessive and prolonged exposure to cold. Anyone who engages in boating, swimming, and outdoor winter activities should learn and practice safety rules and survival techniques. Everyone, especially the elderly and the debilitated, should have adequate food, clothing, shelter, and sources of heat. Electric blankets may effectively prevent hypothermia, even in inadequately heated houses. Additional information on hypothermia and safety rules may be obtained from sources listed in references 5-9.


  1. National Center for Health Statistics. Current estimates from the national health interview survey: United States, 1979, series 10; no. 141 (computer tape) Hyattsville, Maryland: National Center for Health Statistics, 1981.

  2. U.S. Senate. Hearing before the Special Committee on Aging, November 26, 1979. Washington, D.C.: U.S. Government Printing Office, 1980.

  3. Martyn JW. Diagnosing and treating hypothermia. Can Med Assoc J 1981;125:1089-96.

  4. Reuler JB. Hypothermia: pathophysiology, clinical settings, and management. Ann Intern Med 1978;89:519-27.

  5. National Institute on Aging. Accidental hypothermia: a winter hazard for the old. Bethesda, Maryland: National Institute on Aging (NIH Publication No. (PHS) 81-1464), 1980.

  6. Select Committee on Aging. Hypothermia: a preventable tragedy. A cold weather guide for the elderly. Washington, D.C.: U.S. Government Printing Office (Comm. Pub. No 97-307), 1981.

  7. CDC. Hypothermia: fact sheet. Atlanta: Centers for Disease Control, January 1982.

  8. National Safety Council. Public safety fact sheet: hypothermia. Chicago: National Safety Council.

  9. CDC. Exposure-related hypothermia deaths--District of Columbia, 1972-1982. MMWR 1982;31:669-671.

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