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

Area of Science:

• Environmental Health
• Epidemiology
• Climate Change Impact

Background:

• Tehran has observed a trend of warmer summers over the past three decades.
• Understanding heat-related mortality is crucial for public health planning during extreme heat events.

Purpose of the Study:

• To identify heat waves in Tehran over recent decades.
• To quantify excess mortality associated with heat waves, considering both immediate and delayed effects.

Main Methods:

• An ecological time-series study was conducted in Tehran.
• Generalized linear lagged models (GLLM) with Poisson regression analyzed daily mortality data.
• Maximum daily temperature was used as the exposure variable, with analyses at lag 0, lag 3, and a 7-day moving average, adjusting for air pollutants (ozone and PM10).

Main Results:

• A total of 1069 excess deaths (8.9 deaths/heat wave day) were recorded across 17 heat waves.
• Significant increases in non-external cause mortality (3-9%) were observed during heat waves, persisting after adjustment for air pollutants.
• Cause-specific deaths, particularly from circulatory diseases, and mortality among the elderly increased during heat waves, with the hottest waves showing the largest effects.

Conclusions:

• Hot temperatures, exacerbated by air pollutants, contribute to excess mortality in Tehran, aligning with climate change trends.
• Evidence of both immediate and lagged mortality effects was found, though the pattern of mortality displacement requires further investigation.