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. 2025 Nov 22.
doi: 10.1007/s00420-025-02179-y. Online ahead of print.

Extreme temperatures, recent warming and seasonal influenza-linking human exposures to respiratory health in southern Germany

Matteo Boser  1   2 , Daria Luschkova  3   4 , Monika Seemann  3   5 ; EXTREME Study Group; Claudia Traidl-Hoffmann #  3   5   6 , Maria P Plaza #  3   5
Collaborators, Affiliations

Extreme temperatures, recent warming and seasonal influenza-linking human exposures to respiratory health in southern Germany

Matteo Boser et al. Int Arch Occup Environ Health. .

Abstract

Purpose: In the context of climate change, extreme ambient temperatures pose a major threat to human health. This study aims to provide detailed insights into how extreme temperatures and potential confounders affect respiratory morbidity.

Methods: We employed a 14-year time series analysis (2006-2019) in southern Germany, applying penalized distributed lag non-linear models to estimate exposure-response relationships between extreme temperatures and respiratory health outcomes, considering emergency outpatient treatments and hospital admissions at the emergency department of the University Hospital Augsburg. We thereby explored the roles of relative humidity and seasonal influenza as potential confounders and vulnerabilities related to age and gender.

Results: We found significantly elevated relative risks (RRs) for the short-term cumulative effect (Lag: 0-3 days) of extreme heat and the long-term cumulative effect (Lag: 0-21 days) of extreme cold on outpatient treatments and hospital admissions. Seasonal influenza was identified as a significant confounder, with attributable fractions comparable to those of cold temperatures. A sub-period analysis (2006-2012 and 2013-2019) revealed a correlation between the recent rise in temperature and the strong increase in the estimated short-term cumulative effect of extreme heat on hospital admissions (2006-2012, RR: 1.08 (95%CI [0.91, 1.27]) vs. 2013-2019, RR: 1.32 (95%CI [1.15, 1.51]).

Conclusion: Our study demonstrated that extreme temperatures significantly affect respiratory morbidity, with notable influences from seasonal influenza. Sub-period analysis indicated that rising temperatures are already translating into measurable effects on respiratory health, foreshadowing the potentially devastating impacts of global warming on human health. Our results thereby provide highly relevant insights to support targeted public healthcare interventions.

Keywords: Climate change; Extreme temperature; Health care utilization; Respiratory health; Time series analysis; Vulnerable populations.

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Conflict of interest statement

Declarations. Conflict of interest: The authors have no competing interests to declare that are relevant to the content of this article. Ethical approval: The study was approved by the ethics committee of the Technical University of Munich (TUM) (sign: 2023-112-S-NP) and the ethics committee of the Ludwig Maximilian University of Munich (LMU) (sign: 23-1035).

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