Hypothermia-Related Deaths -- New Mexico, October 1993-March 1994

Hypothermia is an unintentional lowering of the body temperature to less than or equal to 95 F (less than or equal to 35 C) (1). From 1979 through 1992, 10,550 persons in the United States died from hypothermia, an average of 754 deaths per year (range: 557-1021). Most of these deaths occurred during winter months in three distinct climatic areas: northern states characterized by moderate to severe cold temperatures during winter (e.g., Illinois and New York); southern states where rapid changes in temperature occur because of the effects of weather systems (e.g., North Carolina, South Carolina, and Virginia); and western states in areas of high elevations and profound declines in temperatures at night (e.g., New Mexico and Arizona). From October 1993 through March 1994, a total of 23 deaths attributed to hypothermia were reported to the New Mexico Office of the Medical Investigator. This report summarizes the investigations of four of these deaths and the epidemiology for all 23 cases.

Case Reports

Case 1. In November 1993, an 85-year-old man was found dead in a drainage ditch behind a factory approximately 1 mile from the nursing home in which he resided. He was fully clothed, and there were no indications of trauma. Water in the drainage ditch was 3 inches deep; the overnight ambient low temperature had been approximately 45 F (7 C). The man had last been seen by the nursing staff 12 hours before being found.

Case 2. On November 1, 1993, an 81-year-old woman was found dead in a shallow creek in an area of heavy plant growth known to house homeless persons. There were no indications of trauma. She had last been seen by her daughter on October 26 and was reported missing on November 1. She had a history of high blood pressure and arteriosclerotic coronary vascular disease.

Case 3. In January 1994, an 11-year-old boy was found in his bed wet, cold, and without a pulse. Attempts to revive him were unsuccessful. The toilet in a bathroom above his bedroom had overflowed and water had been dripping on him all night. He had a history of cerebral palsy, hydrocephalus, and seizure disorder; was blind, deaf, and unable to speak; and had impaired mobility that limited his ability to turn over.

Case 4. In February 1994, a fully clothed 34-year-old man was found dead behind a grocery store after an overnight low temperature of 13 F (-11 C). He had a history of alcohol abuse and cerebral injuries and he was found with a prescription vial of phenytoin in his pocket. He had last been seen alive in the field behind the store searching for a plastic sack in which to keep warm during a snow storm.

Summary of Cases

Of the 23 deaths, seven (30%) occurred during February, and 17 (74%) occurred among men. The average age of decedents was 49 years (range: 11-87 years). Eleven (48%) had evidence of recent alcohol abuse. Eight (35%) deaths occurred in McKinley County, which is in a desert area with elevations greater than 5000 feet above sea level.

Reported by: R Zumwalt, MD, D Broudy, MPH, Office of the Medical Investigator, New Mexico. Div of Environmental Hazards and Health Effects, National Center for Environmental Health, CDC.

Editorial Note

Editorial Note: From 1979 through 1992, the highest total number of deaths attributed to hypothermia occurred in Illinois (660), and the highest annual age-adjusted death rate (33 deaths per million persons) occurred in Alaska. However, the findings in this report underscore the risk for hypothermia-related deaths in states in other latitudes. Of the 10 states with the highest combined ranking for both number and rate of hypothermia deaths, only two (Illinois and Alaska) are characterized by severe winter weather; the winter climate is substantially milder in the other eight states (Alabama, Arizona, New Mexico, North Carolina, Oklahoma, South Carolina, Tennessee, and Virginia).

From 1979 through 1992, national death rates for hypothermia varied by sex, race, and age. Although most deaths occurred among males (71%) and whites (61%), sex- and race-specific average annual death rates were higher for black males than white males (13.1 versus 3.2 deaths per million) and for black females than white females (4.1 versus 1.4 deaths per million). * Approximately half of all hypothermia deaths occurred among persons aged greater than 64 years. These demographic differences in hypothermia mortality may reflect differences in socioeconomic status, nutritional status, condition of clothing, or ease of access to adequate shelter.

Factors associated with the increased risk for hypothermia in the very young and the elderly in mildly cool environments (65 F {18 C}) include an impaired shivering mechanism, lower levels of protective fat, limited mobility, lower metabolic rate, and chronic illness (2). Other risk factors associated with hypothermia for all groups include drinking alcoholic beverages, using neuroleptic medications, hypothyroidism, mental illness, starvation, dehydration, poverty, any immobilizing illnesses, and sustained contact with material that promotes conductive heat loss (e.g., water, solvents, and metals) (2).

The onset of hypothermia is insidious: early manifestations include shivering, numbness, fatigue, poor coordination, slurred speech, impaired mentation, blueness or puffiness of the skin, and irrationality (3). Early recognition and prompt treatment can prevent morbidity and death. Specific prevention measures during cold and inclement weather conditions include maintaining dry clothes and wearing layered, insulated clothing (particularly head gear, because 30% of heat loss occurs from the head) that does not retain moisture (e.g., wool or polypropylene). In addition, persons who are outdoors in such conditions for extended periods should increase their fluid and calorie intake, find adequate shelter, and avoid overexertion and sweating. Persons at increased risk for hypothermia during such periods should be monitored by family and neighbors.

High death rates in states with relatively mild winter climates reflect, in part, the need for increased efforts to inform the public and high-risk groups about the health risks of environmental cold and about measures for preventing hypothermia. During cold weather, health-care providers, public health agencies, community-services organizations, and others can reduce the occurrence of hypothermia-related morbidity and death by monitoring groups at elevated risk during cold weather and ensuring that adequate shelter is provided.

References

1. Kilbourne EM. Cold environments. In: Gregg MB, ed. The public health consequences of disasters. Atlanta: US Department of Health and Human Services, Public Health Service, CDC, 1989:63-8.

2. Merck Research Laboratories. The Merck manual of diagnosis and therapy. Rahway, New Jersey: Merck Research Laboratories, 1992.

3. CDC. Hypothermia -- United States. MMWR 1983;32:46-8.

Numbers for other racial/ethnic groups were too small for meaningful analysis.

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