Ensemble Bayesian modelling with dynamic population to estimate excess deaths due to extreme temperatures

Area of Science:

• Environmental Health
• Epidemiology
• Biostatistics

Background:

• Extreme heat events are increasingly recognized as a significant public health threat, contributing to elevated mortality rates.
• Effective heat adaptation policies, including timely heat warnings, necessitate accurate monitoring of heat-attributable mortality burdens.
• Identifying vulnerable populations and understanding temperature thresholds are critical for mitigating heat-related deaths.

Purpose of the Study:

• To evaluate the excess mortality associated with extreme heat during summer 2022 in Switzerland.
• To identify specific populations vulnerable to heat-related mortality.
• To estimate temperature thresholds relevant for developing and refining heat adaptation strategies.

Main Methods:

• Utilized nationwide mortality and population data from 2011-2022, stratified by age, sex, day, and canton.
• Developed a Bayesian ensemble modeling approach incorporating dynamic population data to predict expected mortality.
• Calculated excess mortality by comparing predicted and observed deaths, controlling for covariates like national holidays and spatiotemporal effects, and accounting for COVID-19 pandemic impacts.

Main Results:

• A total of 487 excess deaths (95% Credible Interval: 10-935) were observed in individuals over 80 years old during summer 2022 in Switzerland.
• Analysis revealed that for extreme heat periods exceeding four days, the minimum excess mortality temperature threshold for the oldest age group corresponds to the 70th percentile of ambient temperature.
• The study highlights that even lower temperature thresholds become significant during extended periods of extreme heat.

Conclusions:

• The findings underscore the substantial mortality burden of extreme heat, particularly among the elderly population in Switzerland.
• The identified temperature thresholds suggest a need for revised heat adaptation policies that consider the duration of heat events.
• Integrating insights on lower temperature thresholds during prolonged heatwaves into public health strategies is essential for preventing heat-related mortality.