Climate, Air Quality, and Emergency Department Use in Northern Germany: Protocol for a Multicenter Register Study

Abstract Background Climate change threatens population health through temperature extremes, air pollution, and altered infectious disease patterns. Emergency departments (EDs) are sensitive indicators of climate-related health impacts; however, comprehensive multicenter investigations integrating meteorological factors, air quality, and infectious disease surveillance across different health care provision levels remain scarce in Germany, particularly in maritime climate regions. Objective This study aims to characterize the impact of meteorological factors, air quality, and infectious disease dynamics on ED presentations across multiple health care facilities and care provision levels in northern Germany over an 11-year period. Methods This retrospective, multicenter, observational study will examine ED presentations across 4 facilities representing different care provision levels in the greater Lübeck area and southeastern Schleswig-Holstein, Germany, from January 2014 to December 2024. Clinical data, including ICD ( International Classification of Diseases )–coded diagnoses, patient demographics, and temporal information, will be linked with meteorological data from the German Weather Service, air quality measurements from state environmental monitoring, and infectious disease surveillance from the Robert Koch Institute. The primary outcomes will be daily ED visits overall and stratified by disease category (cardiovascular, respiratory, psychiatric, infectious, renal, neurological, and surgical/traumatic). Distributed lag nonlinear models within a generalized additive modeling framework will be used to characterize temperature-health relationships, accounting for delayed and nonlinear effects, and adjusted for temporal trends, seasonality, and infectious disease incidence. Subgroup analyses will examine vulnerable populations by age, sex, and socioeconomic status. Results Project planning and conceptualization began in June 2024, and ethical approval was granted in July 2025. Following approval, clinical data were transferred sequentially across participating sites in July 2025, August 2025, and October 2025. Data from 3 of the 4 participating hospitals have been successfully received, while the final outstanding dataset is expected in the second half of 2026. Meteorological data collection was completed in October 2025 and air quality data in January 2026. While preliminary descriptive statistical analyses have already commenced, inferential statistics will be performed once data collection is fully completed. Conclusions This multicenter study will provide systematic evidence on climate-sensitive ED utilization in a maritime climate region of northern Germany. By integrating clinical, meteorological, air quality, and infectious disease data across 4 hospitals of varying care complexity, the study is well positioned to characterize nonlinear and delayed health effects of temperature extremes across a broad spectrum of acute conditions. Results are expected to inform regional health care capacity planning, early warning systems, and public health preparedness, while contributing to the broader evidence base on climate and health.