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Originally published by 2 Minute Medicine® (view original article). Reused on AccessMedicine with permission.

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1. Nevada gun shows were linked to local, temporary increases in firearm-related injuries and deaths in California, but California gun shows were not.

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2. Considering that some of the most restrictive firearms laws are in California and some of the least restrictive are in Nevada, study results suggest that the difference in association between gun shows located in these two states may be related to California’s stricter firearm laws.

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Evidence Rating Level: 2 (Good)

Study Rundown:

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In the United States, firearms are a top cause of injury and death. Owning a firearm increases these risks. Each year, over 4 000 gun shows are held in the U.S. Firearm sales may have less oversight at these gun shows, which may result in increased firearm ownership in local areas. This quasi-experimental study aimed to establish whether or not gun shows are linked to temporary increases in firearm injuries (including deaths) in the local area and whether or not this link varies by the state where the gun show took place. Considering that some of the most restrictive firearms laws are in California and some of the least restrictive are in Nevada, researchers focused on data relating to these two states. The authors found that gun shows located in Nevada were linked to local, temporary increases in firearm-related injuries in California, but gun shows located in California were not. The difference in association between gun shows located in these two states may be related to California’s stricter firearm laws.

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Strengths of the study include being statistically well-powered and including firearm injuries that were nonfatal, unintentional, and with undetermined intent rather than only including suicides and homicides caused by firearms. Limitations of the study include the examination of firearm injuries only in California and the non-random occurrence of gun shows.

In-Depth [quasi-experimental]:

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Using a quasi-experimental, difference-in-differences design, researchers evaluated whether or not the timing and location of gun shows were linked to changes in firearm injuries (including deaths) and whether or not the link differed by the state where the gun show was held. The authors studied 640 gun shows held in California and 275 held in Nevada between 2005 and 2013. The authors compared rates of injuries due to firearms for the two weeks directly before and after gun shows in areas of California that were within convenient travel distance of each gun show. These differences were then compared to California residents exposed to gun shows in California versus Nevada. In this way, each area functions as its own control. Researchers found that postshow rates of firearm injuries were stable in comparison to preshow rates in areas near California gun shows but increased from 0.67 to 1.14 injuries per 100 000 persons in areas near Nevada gun shows. This link corresponds to 30 more injuries in California areas exposed to Nevada gun shows. Gun shows in California were not linked to local firearm injury rate increases (rate ratio [RR], 0.99 [CI, 0.97 to 1.02]), but gun shows in Nevada were linked to California firearm injury rate increases (RR, 1.69 [CI, 1.16 to 2.45]). Injuries not caused by firearms were used as a negative control and were not linked to gun shows held in either state.

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