Lag effect on the risk of ambulance transport due to heatstroke

Heatstroke is a well-known heat-related illness in summer, and the number of ambulance transports in Japan due to heatstroke is increasing as the number of patients increases each year. The risk of heatstroke depends mainly on the weather conditions on the day of heatstroke, but it is unclear how long the risk persists and to what extent it decreases with time. In this study, lag effects on the risk of heatstroke ambulance transport were investigated using a Distributed Lag Non-linear Model.  Ambulance transport data provided by the Toyohashi Fire Department Japan were used in this study (data period : 2011-2022 (from June to September in each year)).  Some results showed that 1) the risk of ambulance transport was 5.40 on the day and 2.19 on the next day (the risk of 1 was defined as the temperature was 29C) under the high temperature condition (34C), and it took two days for the transport risk to return to 1. 2) the older, the higher the transport risk (4.49 for those over 65 years old and 6.69 for those under 65 years old). However, regardless of age, it took two days for the risk to return to 1. 3) The effect of air conditioning (ON/OFF) on the transportation risk was 2.29 (AC ON) and 3.79 (AC OFF) on the day of heatstroke.