Ecologic factors relating to firearm injuries and gun violence in Chicago

• Ecologic variables related to firearm-related injuries and crime were explored.
• The Illinois Trauma Registry and the Chicago Police Department's CLEAR were analyzed.
• Weekday, daily temperature, and rain are associated with firearm injuries and crime.
• Snow was not found to be associated with either firearm-related injuries or crime.

BackgroundFirearm 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.MethodsThe 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.ResultsA 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.ConclusionsDay 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.