Year: 2026
Type: preprint
Study design: Observational Study
Abstract: Background Multiple factors can drive heat susceptibility but are typically analyzed individually. This study investigates high-dimensional heterogeneity across multiple domains in the effect of hot days on emergency hospitalizations across German districts. Methods We obtained emergency hospitalization rates per 1,000 in 3-day windows for the summers of 2005-2023 from the German Diagnosis-Related Groups-Statistic, linked with spatio-temporal temperature information. A hot day was defined as at least one day above the district-level 98th percentile heat index. Multiple characteristics of the demographic, health/social, and environmental domains were selected as effect modifiers. We implemented a generalized random forest, where outcome and propensity scores were modeled with fixed effects estimators to control for seasonality and district-level confounding. We divided the conditional average treatment effects into quartiles to map their spatial distribution and identify key effect modifiers via the variable importance and observed indicator profiles across quartiles. Results While the average effect of heat on emergency hospitalizations was close to null (-0.3 per 1,000), effects in the lowest and highest effect quartiles ranged from -2.3 to +1.4 per 1,000. Demographic indicators explained the largest share of heterogeneity (34.5%), followed by environmental (14.53%) and health/-social factors (10.28%). The indicator profile for the most susceptible districts was characterized by lower air pollution levels, a larger percentage of vulnerable populations, and higher car density. Conclusion We highlight that heat susceptibility cannot be summarized by one number per region or be explained by a single effect modifier, which needs to be considered in heat-health warning systems and adaptation planning.
Source: medRxiv
Institutions: Robert Koch Institute, Max Planck Institute for Demographic Research, Scripps Institution of Oceanography, Inserm, École des Hautes Études en Santé Publique, University of California San Diego, Institut de Recherche en Santé, Environnement et Travail, Université de Rennes, University of Helsinki, Karolinska Institutet
Language: English
Subfield: Health, Toxicology and Mutagenesis
Field: Environmental Science
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7214232790