Current Trends Heat-Related Deaths -- Missouri, 1979-1988

From 1979 through 1988, 491 deaths were attributed to excessive heat exposure* in Missouri. More than half of these occurred during a 1980 heat wave (Figure 1). Although heat-related mortality is also influenced by factors such as humidity and regional acclimatization (1), trends for heat-related deaths in Missouri during 1979-1988 paralleled the state's average summer temperatures** (Figure 1).

Persons greater than or equal to 65 years of age were the most severely affected, accounting for 330 (67.2%) of the deaths (Table 1). The mortality rate for this population was 48.7 per 100,000 persons, compared with 3.8 per 100,000 for persons less than 65 years of age. The rate for nonwhites was substantially greater than that for whites, even after controlling for age (Table 1). For persons less than 65 years of age, the rate for males was twice that for females; in contrast, gender-specific rates for persons greater than or equal to 65 years of age were similar (Table 1). Reported by: SE Stewart, B Gibson, G Land, Div of Health Resources, Missouri Bur of Health Data Analysis, D Rackers, HD Donnell Jr, MD, State Epidemiologist, Missouri Dept of Health. A Graumann, User Svcs Br, National Climatic Data Center, National Oceanic and Atmospheric Administration. Health Svcs Br, Div of Environmental Hazards and Health Effects, Center for Environmental Health and Injury Control, CDC.

Editorial Note

Editorial Note: Growing scientific and public concern about the potential for global warming due to the "greenhouse effect" has focused attention on the health effects of heat during the summer (2). Heat-related mortality during July 1980 demonstrated the effect that high temperatures can have on health (3). Missouri, which reported greater than 17% of the nation's 1716 heat-related deaths in 1980, maintains active surveillance of such deaths as part of a system for early detection and prevention of heat-related morbidity and mortality.

Most heat-related deaths result from heatstroke, a severe illness in which thermoregulatory failure results in core body temperatures exceeding 105 F (40.6 C). Heatstroke is a medical emergency that can develop in a few minutes or hours. Symptoms are primarily those of altered mental status and can progress from lethargy and confusion to stupor and coma as the body temperature rises; anhidrosis may occur, but many heatstroke patients perspire profusely. Treatment includes the rapid lowering of body temperature followed by intensive supportive care. Heatstroke is often fatal ( greater than 40%), even when treatment is optimal (4,5).  The elderly are at greatest risk for heat-related illness, especially those who have chronic illness and/or take medications that might predispose to heatstroke. Also at increased risk are infants and children less than 4 years old, particularly those with congenital abnormalities of the central nervous system or with diarrheal illness; alcoholics; persons taking neuroleptic medications (antipsychotics or major tranquilizers) or anticholinergic drugs (e.g., tricyclic antidepressants, antihistamines, some antiparkinsonian agents, and over-the-counter sleeping pills); and persons who are physically or mentally impaired (5).

Additional risk factors include a prior history of heatstroke; certain uncommon conditions such as congenital absence of sweat glands, systemic sclerosis, and hyperthyroidism; and exercising in the heat without proper training and acclimatization. Obesity increases the risk for exercise-induced heatstroke (5). Although racial differences in heat-related deaths have been reported, attempts to assess the separate contributions of race and socioeconomic status to heatstroke risk have been largely unsuccessful (3); there is no evidence of a biologic predisposition for heatrelated death associated with race.

Preventive measures include reducing physical activity, drinking extra liquids, and increasing time spent in air-conditioned places (6). Adequate salt intake is important; however, salt tablets are not recommended for preventing heatstroke in the general population and may be harmful to persons with certain preexisting illnesses such as hypertension and heart failure (3,7). At very high temperatures (high 90s and above), fans are ineffective for cooling and may increase heat stress and the risk of heatstroke (8,9). Therefore, persons without home air-conditioners should seek shelter in an air-conditioned environment rather than rely on the use of electric fans (6).

References

1. Kalkstein LS, Davis RE. Weather and human mortality: an evaluation of demographic and interregional responses in the United States. Ann Assoc Am Geographers 1989;79:44-64.

2. Schneider SH. The greenhouse effect: science and policy. Science 1989;243:771-81.

3. Jones TS, Liang AP, Kilbourne EM, et al. Morbidity and mortality associated with the July 1980 heat wave in St. Louis and Kansas City, Missouri. JAMA 1982;247:3327-31.

4. Hart GR, Anderson RJ, Crumpler CP, Shulkin A, Reed G, Knochel JP. Epidemic classical heat stroke: clinical characteristics and course of 28 patients. Medicine 1982;61:189-97.

5. Kilbourne EM. Illness due to thermal extremes. In: Last JM, ed. Maxcy-Rosenau--public health and preventive medicine. 12th ed. New York: Appleton-Century-Crofts, 1986:703-14.

6. Kilbourne EM, Choi K, Jones TS, Thacker SB. Risk factors for heatstroke: a case-control study. JAMA 1982;247:3332-6.

7. Pitts GC, Johnson RE, Consolazio FC. Work in heat as affected by intake of water, salt and glucose. Am J Physiol 1944;142:253-9.

8. Lee DHK. Seventy-five years of searching for a heat index. Environ Res 1980;22:331-56.

9. Steadman RG. A universal scale of apparent temperature. J Climate Applied Meteorol 1984;23:1674-87. *Deaths attributed to excessive heat exposure are coded E900 according to the International Classification of Diseases, Ninth Revision. **Based on "State Areally Weighted Temperatures" provided by the National Climatic Data Center, National Oceanic and Atmospheric Administration.

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