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Perspectives in Disease Prevention and Health Promotion
Hypothermia-Associated Deaths -- United States, 1968-1980
Mortality data from the National Center for Health Statistics
show
that, during the 13-year period from 1968 to 1980, 6,460 deaths
were
attributed to the effects of cold. The risk of death from
hypothermia
varies by both age and sex (Table 1). After the first year of
life,
death rates increase with age; elderly persons are at highest risk
of
mortality. A clear differential exists between the sexes, with the
rates for males exceeding those for females for all but one age
group. This differential is largest for persons 10-14 years of
age,
when males are almost nine times more likely to die from
hypothermia.
For this period, the age-adjusted mortality rate (deaths per
million
persons) for males was 4.2, compared with 1.0 for women.
Reported by Div of Environmental Hazards and Health Effects, Center
for Environmental Health, CDC. Editorial Note
Editorial Note: Since hypothermia is an important cause of
mortality
in the United States during the winter season, and recent reports
indicate that mortality rates have increased (1,2), physicians
should
be familiar with the diagnostic criteria and risk factors for
hypothermia.
Hypothermia is defined as a lowering of core body temperature
to
35 C (95 F) or below. The severity of hypothermia is indicated by
the
degree to which core temperature is lowered: mild hypothermia
(34-35
C (93-95 F)); moderate hypothermia (30-34 C (86-93 F)); and severe
hypothermia (less than 30 C (86 F)). Hypothermia can also be
classified as primary or secondary. Primary hypothermia results
directly from an overwhelming cold stress, whereas secondary
hypothermia is part of other clinical conditions. Clinical
syndromes
associated with secondary hypothermia may be acute and severe, such
as
shock or sepsis.
Signs of hypothermia include poor coordination, stumbling,
slurred
speech, irrationality and poor judgment, amnesia, hallucinations,
blueness or puffiness of the skin, dilation of the pupils,
decreased
respiratory rate, weak or irregular pulse, and stupor (3).
Symptoms
of hypothermia include muscle tensing, fatigue, a feeling of deep
cold
or numbness, intense shivering, poor coordination, stumbling, and
disorientation (3). Unfortunately, these signs and symptoms are
nonspecific. The only reliable method of diagnosis is measuring
core
body temperature. Accurate diagnosis is often hindered because
thermometers are used that measure body temperature only in the
range
of 35-42 C (95-104 F). For accurately measuring core body
temperature, rectal, rather than oral, temperature should be taken
with a low-reading thermometer capable of measuring temperatures
from
25 C to 40 C (77 F to 104 F) (4).
The highest mortality rates occur in the elderly. Studies of
the
regulation of body temperature in the elderly show that physiologic
and behavioral components of thermoregulation contribute to an
increased vulnerability to hypothermia. Both vasoconstriction and
shivering, two primary adaptive physiologic measures to conserve
heat,
appear to be decreased in some elderly individuals (5-7). Other
studies of the behavioral aspects of the response to cold show
that,
while the elderly prefer temperatures similar to those preferred by
the young, a significant number do not discriminate temperatures
well,
lack precision in adjusting the thermal environment (8), and are
less
comfortable in cold environments (9).
Gender as a risk factor has been shown in a previous report
(10),
with males being at greater risk. This could be the result of
differences in factors related to physical condition and behavior.
Some of these factors include poor physical condition, inadequate
nutrition, inadequate insulation/protection or increased exposure
to
wind, rain, and snow, fatigue, alcohol intoxication, drug overdose,
and illness. These factors influence the rate at which the body
loses
heat when exposed to cold temperatures (4).
Several appropriate prevention goals exist for reducing the
risk
factors of hypothermia. One goal is to educate the elderly and
their
health-care providers on the etiology, symptoms, and significance
of
hypothermia. In implementing this strategy, the elderly who live
in
poverty and social isolation should be identified and followed.
Cases
of hypothermia, or situations hastening the onset of hypothermia,
could then be more readily recognized and corrected. Another goal
is
to assure adequate food supply and intake. The production of
optimal
body heat from metabolic processes will lessen the risk of
hypothermia. Finally, assuring adequate space heating is a key
preventive measure. For younger persons at risk, activities and
travel during cold weather should be attempted only with sufficient
clothing and planning, e.g., keeping blankets in the car and the
gas
tank always at least half full.
References
CDC. Hypothermia--United States. MMWR 1983;32:46-8.
Rango N. Exposure-related hypothermia mortality in the United
States, 1970-79. Am J Public Health 1984;74:1159-60.
CDC. Hypothermia fact sheet. Atlanta, Georgia: U.S.
Department
of Health, Education, and Welfare, Public Health Service,
Centers
for Disease Control, January 1982.
Collins KJ. Hypothermis: the facts. New York: Oxford
University Press, 1983.
Collins KJ, Dore C, Exton-Smith AN, Fox RH, et al. Accidental
hypothermia and impaired temperature homoeostasis in the
elderly.
Br Med J 1977;1:353-6.
Collins KJ, Easton JC, Exton-Smith NA. Shivering thermogenesis
and vasomotor responses with convective cooling in the elderly.
(Abstract) J Physiol 1981;320:76.
Wagner JA, Robinson S, Marino RP. Age and temperature
regulation
of humans in neutral and cold environments. J Appl Physiol
1974;37:562-5.
Collins KJ, Exton-Smith AN, Dore C. Urban hypothermia:
preferred
temperature and thermal perception in old age. Br Med J
1981;282:175-7.
Watts AJ. Hypothermia in the aged: a study of the role of
cold-sensitivity. Environ Res 1972;5:119-26.
CDC. Exposure-related hypothermia deaths--District of
Columbia,
1972-1982. MMWR 1982;31:669-71.
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