Epidemiologic Notes and Reports Illness and Death Due to Environmental Heat -- Georgia and St. Louis, Missouri, 1983

Much of the eastern, central, and southern United States experienced higher-than-normal temperatures during the summer of 1983. St. Louis, Missouri, and the state of Georgia were among the areas affected by the heat wave (1). Health officials from these areas noted an increased incidence of death and illness attributable to heat during this time.

In St. Louis, there were 348 cases of heat-related illness (HRI)* and 35 heat-related deaths (HRD)** between July 11 and August 15. Of those who died, 23 (65.7%) were elderly (aged 60 years and over), 27 (77.2%) were female, and 23 (65.0%) were black. Heat-related mortality rates were 22.2 per 100,000 persons for the elderly and 3.43/100,000 for those under 60 years of age. The rates were 11.1/100,000 for blacks and 5.0/100,000 for whites; 5.0/100,000 for females and 3.9/100,000 for males.

In Georgia, 804 cases of HRI and 35 HRDs were reported, a substantial increase from the 96 HRIs and three HRDs in 1982, when average temperatures for July and August were 4-5 F below those in 1983. Patients over 60 years of age were the most severely affected, accounting for 20 (57.0%) of the deaths and 147 (26.0%) of the HRIs throughout the state.*** The mortality rate for the over-60 population was 3.2/100,000 persons and 0.3/100,000 for the population aged 60 and under. Sixteen (45.7%) of the deaths were among blacks, giving them a mortality rate (1.1/100,000) about twice that of whites (0.5/100,000). Males had a mortality rate of 0.8/100,000 and females a rate of 0.5/100,000.

The heat-related deaths occurred primarily during short periods of especially hot weather. Over half of the Georgia HRDs occurred between July 19 and July 28, when Atlanta reported mean daily temperatures**** between 34.4 C and 37.2 C (94.0 F and 99.0 F), an average of 6 F above normal for that time period (2). In St. Louis, 89.0% of the HRDs occurred between July 19 and July 25 when mean daily temperatures averaged 31.7 C (89.0 F), 10 F above normal (3). Reported by W Hope, ScD, St. Louis Health Div, HD Donnell, Jr, MD, State Epidemiologist, Missouri Dept of Social Svcs; TW McKinley, MPH, RK Sikes, DVM, State Epidemiologist, Georgia Dept of Human Resources; Special Studies Br, Chronic Diseases Div, Center for Environmental Health, CDC.

Editorial Note

Editorial Note: Most deaths directly attributable to heat result from heatstroke. This is a condition characterized by a substantial elevation in core body temperature, generally to 40.5 C (105.0 F) or higher, with temperatures above 43.3 C (110.0 F) not uncommon. The patient will appear confused, and may progress to stupor and unconsciousness as the body temperature rises. Anhidrosis (absent sweating) may be noted, but many heatstroke patients perspire profusely. Treatment is directed toward the rapid lowering of body temperature followed by intensive, supportive care. Heatstroke is often fatal, even when treatment is optimal (4).

Age-specific heatstroke rates for the summer of 1983 in St. Louis and Georgia reveal the marked predisposition of the elderly to develop heatstroke, a finding that is consistent with previous observations (5). Older persons regulate their thermal environment less well than young people (6). In addition, the elderly have a greater frequency of chronic illness and are more likely to use medications which may predispose to heatstroke (7). Thus, the elderly should be considered a high-risk group for heatstroke during periods of sustained hot weather.

Both St. Louis and Georgia data show blacks to have had higher heatstroke rates than whites. While this finding has been previously reported, differences in socioeconomic status (SES) confound comparisons of heatstroke rates for blacks and whites. Attempts to assess the separate contributions of race and SES to heatstroke risk have been largely unsuccessful (5). In St. Louis, the rate of HRD was greatest among females, while the reverse was true in Georgia. These differences may result, in part, from the different patterns of heat exposure in an urban area (St. Louis) and in a state with a substantial rural population (Georgia).

Persons confined to bed or otherwise unable to take care of themselves are at high risk from the heat, as are alcoholics and persons taking neuroleptic or anticholinergic drugs. Reducing physical activity, drinking extra liquids, and increasing time spent in air-conditioned places (even if there is no home air conditioner) all offer substantial protection from heatstroke (7). Fans decrease in cooling efficacy as ambient temperatures rise, and have been found to increase heat stress in very hot weather (8). Thus, the distribution of fans may not be an appropriate public health measure during extreme heat.

During heat waves, heatstroke prevention efforts should focus on those at greatest risk (e.g., the poor, elderly, or chronically ill). Persons at risk should be advised to reduce physical activity, consume extra liquids, and, if possible, seek shelter in an air-conditioned environment for at least part of the day. Although adequate salt intake with meals is important, salt tablets are of doubtful benefit in the prevention of heatstroke, and may actually harm persons with certain preexisting illnesses (e.g., heart failure) (7). Heatstroke rates are increased among alcoholics; moderate alcohol intake, however, may not predispose a person to heatstroke who is not otherwise at risk.

References

1. National Oceanic and Atmospheric Administration. Climate impact assessment: United States. U.S. Department of Commerce. July 1983.

2. National Weather Service Observation Station, William B. Hartsfield Atlanta International Airport, Atlanta, Georgia.

3. National Weather Service Observation Station, St. Louis International Airport, St. Louis, Missouri.

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. 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.

6. Collins KJ, Exton-Smith AN, Dore C. Urban hypothermia: preferred temperature and thermal perception in old age. Br Med J 1981;282:175-7.

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

8. Lee DHK. Seventy-five years of searching for a heat index. Environ Res 1980;22:331-56. *Defined as any hospital admission with a body temperature higher than 40.6 C (105 F). **Defined as any death related to excessive heat, either directly or indirectly through exacerbation of a preexisting medical condition. ***Includes only individuals for whom age was reported. ****Defined as the arithmetic mean of maximum and minimum temperatures of a given day.

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