Six Square Miles of Urban America: Association Between Firearm Discharge, Injury, and Fatality

Despite the increase in firearm injury observed across the country, significant gaps remain relevant to our understanding of how firearm exposure translates to injury. Using acoustic gunshot detection and a collaborative hospital and law enforcement firearm injury database, we sought to identify the relationship between firearm discharge and injury over time.

From 2018 to 2021, instances of firearm discharge captured via acoustic detection in 6 square miles of Louisville, KY, were merged with data from the collaborative firearm injury database. Key outcomes included the total number of rounds fired, injury and fatality rates per round, and the percentage of rounds discharged from automatic weapons and high-capacity magazines.

During the study period, 54,397 rounds of ammunition were discharged resulting in 914 injuries, 435 hospital admissions, 2,442 hospital days, 155 emergent operations, and 180 fatalities. For each round of ammunition fired, the risk of injury and fatality was 1.7% and 0.3%, respectively. The total number of rounds fired per month nearly tripled (614 vs 1,623, p < 0.001) leading to increased injury (15 vs 37, p < 0.001) and fatality (3 vs 7, p < 0.001). The percentage of rounds fired from automatic weapons (0 vs 6.8%, p < 0.001) and high-capacity magazines (7.6 vs 28.9%, p < 0.001) increased over time.

The increased burden of firearm injury is related to an overall increase in firearm exposure as measured by the total number of rounds discharged. High-capacity magazines and automatic weaponry are being used with increasing frequency in urban America.