Optimizing the Placement of Automated External Defibrillators in Marin County, CA — A Location-Allocation Analysis

This study evaluated the spatial and temporal coverage of public automated external defibrillators (AEDs) in Marin County, California, from 2019 to 2024 to determine whether existing AEDs were optimally located to maximize Out-of-hospital cardiac arrest (OHCA) coverage and to identify additional placement opportunities. We defined coverage as the proportion of OHCAs occurring within 100 meters of an AED and differentiated between expected coverage (ignoring AED availability) and actual coverage (accounting for AED accessibility at the time of arrest). Using registry data on 321 publicly available AEDs and geocoded OHCA events, we found no significant difference between expected and actual coverage, suggesting temporal accessibility was not a major limiting factor. However, by incorporating 20 candidate AED sites identified through location-allocation modeling, OHCA coverage significantly improved by 2.93 percentage points (from 7.01% to 9.94%, p < 0.05), representing a 42% relative increase. This suggests that spatial distribution—not temporal availability—is the key for improved coverage in Marin County, and strategic placement of a limited number of additional AEDs could meaningfully enhance public access to defibrillation.