Excess mortality during heat waves, Tehran Iran: an ecological time-series study

In the past three decades, Tehran has experienced warmer summer so we need to determine heat-related mortality to establish appropriate public health activities during hot summers. The aim of the present study was to detect heat waves during the last decades and then determine excess mortality in immediate and lagged times.

An ecological study based on time-series model was conducted in Tehran for recent decade using generalized linear lagged model (GLLM) with Poisson regression. Maximum daily temperature was heat exposure for death outcome on the same day (lag 0), 3 (lag01) and also 7 (lag02) day moving average. Relative risk with 95% confidence was reported to quantify for increasing of daily mortalities for 1°C risen exposure. Air pollutants considered as confounders in final model.

Total excess mortality during 17 heat waves was 1069 (8.9 deaths/Heat wave days). All non-external cause of death increased significantly during heat waves (3-9%) and after adjusting for ozone and PM10, raised. Cause-specific deaths (especially circulatory disease) and death among elderly increased during heat waves (especially in the hottest wave). The largest positive lagged effect of hot temperature although seen during hottest waves for all mortalities. Three waves had the most harvest effect for all categories of mortalities.

Study showed excess mortalities resulted from hot temperatures and exacerbated with air pollutants in Tehran in the context of climate change. Forward displacement mortality and lagged mortalities as well as were seen, but our results were not conclusive about the displacement pattern of mortalities.