Current status of active cooling, deep body temperature measurement, and face mask wearing in heat stroke and heat exhaustion patients in Japan: a nationwide observational study based on the Heatstroke STUDY 2020 and 2021

Aim The study aimed to determine the current status of face mask use, deep body temperature measurement, and active cooling in patients suffering from heat stroke and heat exhaustion in Japan. Methods This was a prospective, observational, multicenter study using data from the Heatstroke STUDY 2020–2021, a nationwide periodical registry of heat stroke and heat exhaustion patients. Based on the Bouchama heatstroke criteria, we classified the patients into two groups: severe and mild‐to‐moderate. We compared the outcomes between the two groups and reclassified them into two subgroups according to the severity of the illness, deep body temperature measurements, and face mask use. Cramer's V was used to determine the effect sizes for a comparison between groups. Results Almost all patients in this study were categorized as having degree III based on the Japanese Association for Acute Medicine heatstroke criteria (JAAM‐HS). However, the severe group was significantly worse than the mild‐to‐moderate group in outcomes like in‐hospital death and modified Rankin Scale scores, when discharged. Heat strokes had significantly higher rates of active cooling and lower mortality rates than heat stroke‐like illnesses. Patients using face masks often use them during labor, sports, and other exertions, had less severe conditions, and were less likely to be young male individuals. Conclusions It is suggested that severe cases require a more detailed classification of degree III in the JAAM‐HS criteria, and not measuring deep body temperature could have been a factor in the nonperformance of active cooling and worse outcomes.