A Step to Develop Heat-Health Action Plan: Assessing Heat Waves' Impacts on Mortality

Abstract: 

Climate change is one of the biggest health threats facing humanity and can directly affect human health through heat waves. This study aims to evaluate excess deaths during heat waves between the summer months of 2004 and 2017 in Istanbul and to determine a definition of heat waves that can be used in the development of an early warning system, a part of prospective urban heat-health action plans. In this study, heat waves were determined using the Excess Heat Factor, an index based on a three-day-averaged daily mean temperature. The death rates during heat waves and non-heat wave days of the summer months were compared with a Z test of the difference of natural logarithms. Thirty heat waves were recorded in Istanbul during the summer months of 2004–2017. In 67% of the heat waves, the death rate was significantly higher than the reference period and 4281 excess deaths were recorded. The mortality risk was especially higher during heat waves of higher intensity. The study showed an excess risk of mortality during heat waves in Istanbul, and the findings suggest that the Excess Heat Factor could be an appropriate tool for an early warning system in Istanbul. 

Introduction 

Anthropogenic climate change causes many extreme weather events all over the world. There is growing evidence of human influence on changes in extreme weather events such as heat waves, heavy rain, and droughts . Studies show that not only the frequency, but also the duration and intensity of heat waves—one of the most common direct effects of anthropogenic climate change—have increased. According to the summary of the Sixth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC) published in August 2021, it is almost certain that extreme heat waves have become more frequent and more intense since the 1950s. In the Eastern Mediterranean region, where Turkey is located, an increase in heat waves has been observed since the 1960s.

Conclusions 

The present study, which used EHF to identify heat waves, showed that a total of 4281 excess deaths occurred in Istanbul during the twenty heat waves that lasted for a total of 257 days in the summer months of 2004–2017. It was also found that the increase in mortality risk was higher in heat waves where high EHF values were long lasting or increased rapidly. These results suggest that EHF is an indicator that can be used in establishing an early warning system in Istanbul. However, studies assessing the relationship of EHF with morbidity, such as ambulance calls, emergency service admissions, and hospitalizations, are also needed for Istanbul.