Ecologic factors relating to firearm injuries and gun violence in Chicago

Firearm violence is a major burden on Chicago with greater than 1500 gunshot injuries occurring annually. Identifying ecologic variables related to the incidence of firearm-related injuries and crime could prove useful for developing new strategies for reducing gun-related injuries.

The Illinois Trauma Registry (ITSR) and the Chicago Police Department's CLEAR (Citizen Law Enforcement Analysis and Reporting) dataset were retrospectively analyzed to investigate group-level factors potentially related to the incidence of gun-related injuries and crime in Chicago from 1999 through 2012. Multivariate linear regression was used to evaluate the effects of day of the week, daily maximum temperature, precipitation, and snow on the incidence of firearm-related injuries and crime.

A total of 18,655 gunshot wounds occurred during the study period (ITSR, 1999-2009). There were 156,866 acts of gun violence identified in the CLEAR dataset (2002-2012). Day of the week, daily maximum temperature, and precipitation were associated with differential risks of gun injury and violence. Rain decreased firearm-related injuries by 9.80% [RR: 0.902, 95% CI: 0.854-0.950] and crime by 7.00% [RR: 0.930, 95% CI: 0.910-0.950]. Gunshot wounds were 33% [RR: 1.33, 95% CI: 1.29-1.37] more frequent on Fridays and Saturdays and gun crime was 18% [RR: 1.18, 95% CI: 1.16-1.20] more common on these days. Snow was not associated with firearm-related injuries or crime.

Day of the week, daily maximum temperature, and rain are associated with the incidence of firearm-related injuries and crime. Understanding the effects of these variables may allow for the development of predictive models and for risk-adjusting injury and crime data.