Severe heatwave in Japan

Abstract

Dear Editor, Despite adequate treatment, heatstroke is often fatal. 1 The incidence of heat-related deaths is increasing with climate change and predicted worldwide increases in the frequency and intensity of heatwaves. 2 Between July 14 and July 24, 2018, the maximal and minimal temperatures throughout Japan reached unusual highs accompanied by extreme humidity, leading to a notable surge in victims of heat-related death nationwide. In fact, Japanese hospitals experienced an unprecedentedly massive admission of heat-related disorders (particularly heatstroke) and deaths. During this period, the mean wet bulb globe temperature (an index of environmental heat stress) of six fixed-point observation cities (Tokyo, Osaka, Nagoya, Hiroshima, Niigata, and Fukuoka) reached 30.9-31.5°C. This is believed to be largely responsible for the deadly epidemic of heatstroke (Fig. 1). In the city of Kumagaya, about 40 miles northwest of Tokyo, the mercury reached 106°F (41.1°C) on July 23-the highest temperature on record in Japan. Within the 11-day period, there were 34,147 cases of heat-related emergency transportation throughout Japan, or roughly 64.4% of the 52,984 cases between May and September of 2017. Of the 34,147 cases, approximately 46.8% (n = 15,994) were aged 65 years and above, 2.9% (n = 997) were diagnosed with heatstroke (regarded as the most severe heat-related illness), and 0.3% (n = 99) were found clinically dead upon the arrival of emergency medical service. 3 In response to this catastrophic heatwave, within a few days of the onset of the sharp increase in heat-related emergency transportations and deaths, the Japanese Association for Acute Medicine issued advisories about the scorching heat, urging people to take measures to avoid heatstroke. 4 Fig. 1. Total numbers of heat-related emergency transportations throughout Japan in July 2017 and July 2018. Green and red (plus black) bars indicate the number of patients with heat-related illness who were transferred by ambulance in July 2017 and July 2018, respectively. Black bar indicates patients with severe heat-related disorders or cardiac arrest on arrival of emergency medical staff at the scene. Purple line indicates the mean wet globe temperatures of six fixed-point observation cities in 2018 (Tokyo, Osaka, Nagoya, Hiroshima, Niigata, and Fukuoka).