Hypothermia is defined as a central or core body temperature of less than or equal to 95 F (less than or equal to 35 C) and is a medical emergency (1). Persons with hypothermia are at high risk for death (2). Although hypothermia-related deaths are common during winter months in states characterized by cold winters (e.g., Alaska and North Dakota) and with mountainous or desert terrain (e.g., Arizona and New Mexico), hypothermia and associated deaths also occur in states with milder climates. For example, during November 1996-April 1997, the Chief Medical Examiner's Office in Virginia identified 20 deaths caused by hypothermia; of these, 11 (55%) were among men and decedents ranged in age from 22 to 86 years (mean: 63 years). This report describes selected cases of hypothermia-related deaths in Virginia during November 1996-April 1997 and summarizes hypothermia-related deaths in the United States during 1979-1994.

Case 1. In December 1996, an 80-year-old woman was found lying dead in a ditch near the nursing home in which she resided. The decedent had Alzheimer disease, Parkinson disease, and congestive heart failure and had been reported missing from the nursing home approximately 12 hours earlier. She was fully clothed, and an autopsy indicated no evidence of life-threatening trauma, preexisting infection, or new intracranial hemorrhage. The outside temperature during the period she was presumed to be outside was approximately 40 F (4 C). There was no detectable blood alcohol. The cause of death was listed as hypothermia attributed to environmental exposure.

Case 2. In January 1997, a motorist found a 45-year-old woman lying dead in a ditch on the side of a road. The body was fully clothed with the torso immersed in water; there were no signs of lethal trauma. The decedent had last been seen alive 3 days earlier, and temperatures during the intervening time had been below freezing. The decedent had a history of alcohol abuse, and an empty wine bottle was found nearby. Her blood alcohol concentration (BAC) was 0.19%; levels were higher in the vitreous humor, indicating that, before death, her BAC had been substantially higher. The cause of death was listed as hypothermia attributed to exposure to environmental cold.

Case 3. In February 1997, an 83-year-old man was found dead in his home. He had no known history of medical problems. He was partially dressed, and there were no signs of traumatic injury. The temperatures during the preceding days had been below freezing, and there was no heat in the house. The cause of death was listed as exposure to cold.

Reported by: M Fierro, MD, Office of the Chief Medical Examiner; SR Jenkins, VMD, State Epidemiologist, Virginia Dept of Health. Health Studies Br, Div of Environmental Hazards and Health Effects, National Center for Environmental Health, CDC.

Editorial Note

Editorial Note: From 1979 through 1994, a total of 11,817 deaths were reported in the United States for which hypothermia was the underlying cause (average annual number and rate: 739 and 0.3 per 100,000 population). * For an additional 9720 deaths, injury attributed to cold was listed as a contributing factor. ** In nearly half (5769 {49%}) of deaths for which hypothermia was the underlying cause, decedents were aged greater than or equal to 65 years (Figure_1). In every age group, the hypothermia-related death rate for males exceeded that for females; for persons aged greater than or equal to 65 years, the rate for men was more than double that for women (1.8 versus 0.8). In addition, for persons aged greater than or equal to 65 years, the death rate for men of black and other races was 6.4 and for white men was 1.4. For women of black and other races, the death rate was 2.5 compared with 0.7 for white women. *** Race-specific differences may have reflected variations in socioeconomic determinants for factors such as access to protective clothing, shelter, and medical care.

In settings of cold exposure, the risk for developing hypothermia is greatest among the elderly, persons who are homeless or mentally ill, outdoor workers, trauma victims, and persons with serious medical conditions (e.g., cardiovascular disease, adrenal disease, and hypothyroidism) (1,2). Other risk factors include excessive alcohol use, exhaustion, poor nutrition, inadequate housing, and drug use (e.g., sedatives, anxiolytics, phenothiazines, and tricyclic antidepressants) (1-3). Hypothermia can occur when even moderately low ambient temperatures (e.g., as high as 60 F {15.5 C}) overcome a person's ability to conserve heat (2).

The prognosis for hypothermia is improved by prompt recognition of the clinical presentation and initiation of treatment. Shivering is an early indication of hypothermia, and a decline in the core temperature can be accompanied by neurologic abnormalities (e.g., amnesia, dysarthria, ataxia, and confusion). Other problems may include hematologic, respiratory, renal, and endocrinologic abnormalities, and severe hypothermia may be characterized by coma, hypotension, apnea, and/or cardiac arrhythmias (4,5). Because most standard thermometers do not record temperatures below 93 F (34 C), use of special equipment (e.g., cold-recording rectal thermometers) may be required for accurately determining core body temperature.

Public health strategies for reducing the risk for hypothermia include public education and programs targeting high-risk populations. Specific preventive measures include wearing adequate clothing (particularly headgear), maintaining fluid and caloric intake, avoiding fatigue, ensuring heated shelter, and refraining from alcohol consumption. In addition, outreach programs should include providing short-term, specialized emergency medical and social services during periods of extreme cold (6) and providing shelter to homeless persons. Workers in cold weather should avoid heavy exertion and wear appropriate protective clothing. Because of the importance of adequate housing during winter months, elderly persons or persons with serious underlying medical conditions who live at home should be monitored by family, neighbors, or social service providers.

References

1. Harrison TR. Principles of internal medicine. 13th ed. New York: McGraw-Hill, 1994:2477.

2. Hector MG. Treatment of accidental hypothermia. Am Fam Physician 1992;45:785-92.

3. Thomas DR. Accidental hypothermia in the sunbelt. J Gen Intern Med 1988;3:552-4.

4. Rom WN. Environmental and occupational medicine. 2nd ed. Boston, Massachusetts: Little, Brown, 1992:1160.

5. Danzl DF, Pozos RS. Accidental hypothermia. N Engl J Med 1994;331:1756-60.

6. Herity B, Daly L, Bourke GJ, Horgan JM. Hypothermia and mortality and morbidity: an epidemiological analysis. J Epidemiol Community Health 1991;45:19-23.

* Data obtained from the Compressed Mortality File maintained by CDC. Hypothermia was defined as the International Classification of Diseases, Ninth Revision (ICD-9), codes E901.0, E901.8, and E901.9 (excludes manmade cold-E901.1). 

** Data obtained from CDC's Multiple Cause of Mortality file. Cases defined by ICD-9, codes E901.0, E901.8, and E901.9 and Nature of Injury code 991. 

*** Data on race/ethnicity were collected only for white, black, and other races. In this analysis, black and other races are grouped together because rates for other races were too small for stable estimates.

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