Emergency Department Utilization and Unplanned Hospitalizations Associated with Floods in the US from 2008-2017: An Interrupted Time Series and Cohort Analysis

Flooding is a major environmental hazard, with events increasing in intensity and frequency in the context of anthropogenic climate change. Significant health and economic impacts result from floods, particularly among vulnerable populations. However, comprehensive analyses of the health consequences of flooding, especially in terms of healthcare utilization and associated costs in the United States, remain limited. Methods: This retrospective study analyzed a decade of data (2008-2017) to assess the impact of large-scale flood events on healthcare utilization among Medicare beneficiaries over age 65 in the United States. Using the Multi-sourced Flood Inventories (MFI) for flood exposure assessment, the study employed an interrupted time-series analysis and a conditional fixed-effects regression approach to explore the incidence of emergency department (ED) visits and hospital admissions pre- and post-flood. Healthcare costs associated with these events were also evaluated, standardized to 2017 USD. Results: The analysis encompassed over 11.8 million Medicare beneficiaries, revealing a statistically significant increase in healthcare utilization following flood exposure. The rate of all-cause ED visits and hospital admissions rose by 4.8% and 7.4%, respectively. Cost analysis indicated an average increase of $17 per exposed individual in Medicare-reimbursed healthcare expenses post-flood and a cumulative increase of over $261 million in national healthcare costs attributable to flooding. Stratified analyses highlighted greater impacts on certain demographic groups, including adults over 85 years, and specific seasonal patterns. Conclusions: Our findings demonstrate a clear association between flood exposure and increased healthcare utilization and costs, underscoring the need for targeted public health strategies and improved disaster preparedness, especially for older adults. This study contributes to a more comprehensive understanding of the health-related costs of flooding, informing future climate change resilience and healthcare planning.