Heat waves are natural disaters that take a heavy toll in human life. During urban summer heat waves in temperate climate, there is frequently a large increase in the daily number of deaths. For example, in July 1980 in St. Louis, Missouri, some 300 more persons died than would have been expected on the basis of death rates observed before and after. In 1995, record breaking heat resulted in the loss of over 700 lives in Chicago, largely in the course of a single week. In fact, more than 150 excess deaths occurred in a single day.
The syndrome of heatstroke is well known to health professionals, manifesting itself as a core body temperature of greater that 105 degrees F and occurring as the result of an external heat stress. Even with optimal treatment, the syndrome has a high death-to-case ratio, 40% or higher in the number of case seris. Although heatstroke deaths occur during heat waves, they frequently account for fewer than half of all heat-wave-related deaths. Death certificates and medical examiner studies have shown that the rest of the death excess is largely attributable to ischemic heart disease (myocardial infarction and related conditions) and cerebrovascular disease (stroke).
Different population groups differ markedly in their susceptibility to the heat. Elderly adults and infants, males, persons of low socioeconomic status, and racial minorities are population groups that appear to be at particularly high risk from the heat. Persons who(1)are unable to care for themselves because of chronic illness, (2) are socially isolated, (3) have suffered previous heatstroke, (4) are alchoholic, and (5) take drugs known as "neuroleptics" (antipsychotic and "major tranquilizing" medications are at markedly increaseed risk.
Electric fans do not offer protection. However, home air conditioning or even partial day visits to air conditioned places substantially decrease risk from heatstroke. One study also showed air conditioning to protect against cardiovascular death during the heat.
The current health recommendations for persons at high risk are to increase the time spent in air conditioned environments, whether at home or elsewhere. In addition, drinking extra liquids (unless there is a mediacal reason not to do so) has been shown to decrease risk.
Despite recent advances in medical science, formulating precise quantitative predictions of the health risk posed by a given set of predicted hot weather conditions remains problematic. Such preditions are important because public health officials need to identify dangerously hot weather sufficiently far in advance to be able to mobilize public health preventive interventions in a timely manner. Studying periods of hot weather that have occured in the same areas in the past and relating those conditions to the extent and patern of mortality that occured may provide an empirical basis for such predictions.