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California gun violence surges 70% after Nevada-hosted gun shows

Research published in the Annals of Internal Medicine indicated that firearm injury rates increased significantly in California, a state with highly restrictive gun laws, in the two weeks after a gun show was held in neighboring Nevada, a state with less restrictive gun laws.

“Little is known about how gun shows contribute to firearm injuries in the United States. ... No formal evaluations have assessed the effects of policies regulating gun shows,” Ellicott C. Matthay, MPH, research data analyst and PhD candidate, School of Public Health, University of California, Berkeley, and colleagues wrote.

Researchers hypothesized that gun shows lead to an increase in firearm-related injury rates. They used a quasi-experimental, difference-in-difference approach to examine firearm violence in Nevada, which they stated has some of the nation’s least restrictive gun-control laws, and in California, which, conversely, has some of the country’s most restrictive gun-control laws. Rates of inpatient hospitalizations, ED visits and deaths related to firearms, as well as information on 915 gun shows held in both California and Nevada between 2005 and 2013, were also collected.

Researchers found that compared with the 2 weeks prior to each California gun show, postshow firearm injury rates remained stable. Conversely, these same rates increased from 0.67 to 1.14 injuries per 100,000 people in areas near Nevada shows.

Matthay and colleagues also found that after adjusting for clustering and seasonality, California shows were not associated with increases in local firearm injuries (RR = 0.99; 95% CI, 0.97-1.02) but Nevada shows were associated with significant cross-border increases in gun-related injuries in California (RR = 1.69; 95% CI, 1.16-2.45).

Researchers also stated gun shows in Nevada were associated with a 70% greater increase in firearm injuries than those in California. In addition, this association corresponded to a rate difference of 0.46 (95% CI, 0.36-0.57) per 100,000 persons, or 30 additional injuries in regions exposed to 161 Nevada shows. The Nevada association was driven by significant increases in firearm injuries from violence between people (RR = 2.23; 95% CI, 1.01-4.89) but corresponded to a small increase in absolute numbers.

They added their study was “strengthened” by expanding the definition of firearm-related injuries and using geographical information that other related studies did not.

“Our study was the first to our knowledge to assess interstate associations and suggests that travel across state lines may be important,” researchers wrote. “[It] avoided several limitations highlighted in critiques of [previous studies] by being well-powered statistically, analyzing data from the show period level rather than the ZIP code–week level, and accounting for California's 10-day waiting period.”

In a related editorial, Ali Rowhani-Rahbar, MD, MPH, PhD and Frederick P. Rivara, MD, MPH, both from the University of Washington, wrote that Matthay and colleagues’ findings have “many implications” for U.S. gun policy.

“Laws regulating access to guns matter and do make a difference, especially collectively; however, their impact on an individual basis is a somewhat small chip in the granite wall of firearm injuries and deaths,” Rowhani-Rahbar and Rivara wrote. “The state-by-state nature of these laws, due to the lack of federal legislation, results in barriers to gun access that can be easily breached by a car trip. It does not reduce the importance of the laws but does reduce their impact.”

Rowhanit-Rahbar and Rivara also added some context to Matthay and colleagues’ findings.

“[Their data] may suggest some association between gun shows and self-directed and unintentional firearm injuries, but the estimates — that is, about 50% to 60% relative increase — were not statistically significant,” they wrote. “It is often forgotten that about two-thirds of firearm deaths in the United States are suicides.” – by Janel Miller

Disclosures: Matthay reports receiving grants from the NIH and University of California, Berkeley, during the conduct of the study. Please see the study for all other authors’ relevant financial disclosures. Healio Family Medicine was unable to determine Rowhani-Rahbar and Rivara’s relevant financial disclosures prior to publication.