ABSTRACT
Objective: To investigate the effect of hourly ambient temperature exposure on emergency calls in Xuchang city and Zhengzhou city. Methods: The hourly meteorological data, air pollution data and emergency calls of Xuchang city and Zhengzhou city were collected from January 1, 2017 to October 31, 2019. A distributed lag non-linear model was used to calculate the excess relative risk (ERR). The lag effect and cumulative effect of extreme temperature exposure on emergency calls were evaluated. Results: The relationship between hourly temperature exposure and emergency calls was a U-shaped curve. In Xuchang city and Zhengzhou city, both low and high temperatures would increase the number of hourly emergency calls. The earliest effect of low temperature occurred at a lag of 22 h and 52 h, with ERR values (95%CI) about 0.20% (0.00%, 0.39%) and 0.11% (0.00%, 0.22%), respectively. The earliest effect of high temperature occurred at a lag of 0 h with ERR values about 1.59% (1.09%, 2.09%) and 1.45% (1.22%, 1.69%), respectively. High temperature had the greatest impact on the number of emergency calls of cardiovascular disease at a lag of 4-8 h. The cumulative ERR values (95%CI) of the two cities were 8.70% (4.98%, 12.75%) and 3.89% (2.61%, 5.22%), respectively. Conclusion: High temperature exposure could increase the number of emergency calls within a few hours, while the effect of low temperature would not occur until 22 hours later.