Impacts of the 2015 Heat Waves on Mortality in the Czech Republic—A Comparison with Previous Heat Waves

The impact of the summer 2015 heat wave on mortality in the Czech Republic was analysed in this study. The findings were compared with a previous record-breaking summer 1994 heat wave.

A mortality baseline was determined using a generalized additive model and daily natural-cause mortality across the country´s population analysed. The mortality deviation from the baseline was calculated in order to quantify the excess mortality during heat waves. This was defined as periods of at least three consecutive days with mean daily temperature higher than the 95^th percentile of annual distribution. The summer 2015 exceeded the summer 1994 in both, the intensity of heat waves and the magnitude of heat-related mortality. Despite the smaller excess mortality associated with the major heat wave in 2015 in comparison to 1994, the relative increase from the baseline was larger in 2015.

The effect of the major 2015 heat wave was more pronounced due to stronger impact on excess mortality among the elderly (65+ years) than the younger age group (0–64 years) in 2015 compared to 1994. The results suggest that the cumulative excess heat factor of a heat wave – considered as a function of absolute temperature anomaly during a heat wave, heat wave duration, and temperature increase relative to the previous conditions – explains the magnitude of excess mortality better during a heat wave than other characteristics such as duration and average daily mean temperature during the heat wave alone.