Heat disorder in Yamanashi Prefecture during the summer from 1995 to 1999

Abstract

Heat disorder in Yamanashi Prefecture during July and August between 1995 and 1999 were investigated using both questionnaires, sent to members of Japanese Medical Association in Yamanashi (62 cases in five years), and also the data-base of patients transported by ambulance (152 cases in five years). As 9 cases were common to both data sets, the total cases reported were 205. The higher the mean maximal air temperature during August, the more incidences occurred. However, a constant tendency toward increase or decrease in the number of incidences over five years could not be recognized. Heat disorders may occur when the environmental temperature was higher than 28°C and the incidence significantly increased when the environmental temperature was above 35°C. The incidence was most significant at the beginning of a sudden increase of air temperature. There were two peaks in the incidence by age group, teenagers and those in seventies. The majority of the incidence (88%) occurred during outdoor exercise or work (or in a gymnasium). Especially in the younger group under sixties (first peak group), all cases, except those occurring in a car, occurred in this situation. However, in the older group above seventies (second peak group), heat disorder occurred during routine outdoor activities (e.g. walking, shopping) or even indoors, when the aged have chronic diseases or takes certain medicaments. The incidence was higher in males than in females (two thirds of cases were in male). Five patients died during 5 years. In 4 of these 5 cases, the core temperature was higher than 40°C and disturbances of central nervous system functions, including confusion or coma, were observed. As treatment, transfusion and, when core temperature was higher than 38°C, body cooling (body surface cooling, instillation of cold liquid, gastric lavage with cold liquid etc) were effective.