Researchers in Washington State took hospital records from 2006 and 2007 and found all the firearm-related hospitalizations (FRH) through diagnosis codes. They then matched those cases with hospitalized patients who were not hospitalized for FRH. They used frequency matching, which is one of the various types of matching you do when conducting a case-control or retrospective cohort study like this one. You can read more about matching here. This was not a case-control study, by the way. It’s a retrospective cohort study. There’s a difference, but that’s for some other day.
The researchers then pulled hospital, police and death records from 2006 to 2011 to see if anyone in the exposed (FRH patients) or unexposed (non-FRH patients) were subsequently hospitalized for a firearm-related injury, were arrested, or died. (Of course, you also want to know what they died from.)
So what do you think? Do you think people who were shot once have a bigger risk of being shot again, arrested, or dying than the risk of the non-FRH patients having similar outcomes? You would think so if certain things are true. If, for example, most of the FRH at baseline were from true accidents, there probably is a lower chance of subsequent hospitalization. (You tend to learn from that kind of mistake.) Or, if you live in a state with not a lot of guns, you’ll probably go a while before seeing subsequent exposures.
On the other hand, if you’re a hospital in an urban setting where there is a lot of poverty, inequality, urban disorder, and such… Well, more on that at the end of June. (Wink. Wink.)
To prevent confusion from re-hospitalization related to the first event, the researchers waited 90 days to begin follow-up. They then set their end date as December 31, 2011. If any of the exposed or unexposed individuals were shot again, killed, or arrested, they would count as an event. The number being analyzed here is how many reach that event before the deadline, and if they reach it at different rates based on their characteristics.
Once they accounted for all the possible confounding factors that they could account for, here’s the big take away from their study:
“In adjusted analyses, patients with an index FRH were at significantly greater risk for a subsequent FRH (sHR, 21.2 [CI, 7.0 to 64.0]), firearm-related death (sHR, 4.3 [CI, 1.3 to 14.1]), and firearm- or violence-related arrest (sHR, 2.7 [CI, 2.0 to 3.5]) than those hospitalized for noninjury reasons.”
Not only is your risk of getting shot again, being arrested for a firearm or violence crime, or dying from a firearm-related cause if you were already shot once… You also have higher risk of other outcomes:
“In addition, patients with an index FRH were at significantly greater risk for nonfirearm assault-related hospitalization (sHR, 7.3 [CI, 3.5 to 14.9]) and nonfirearm nonviolent arrest (sHR, 1.9 [CI, 1.6 to 2.3]) than those hospitalized for noninjury reasons.”
The authors do talk about the limitations to their study, which it seems that they thought of thoroughly:
“The primary limitations of this study pertain to the use of existing records that did not include all potentially useful information. First, CHARS data for the index years in this investigation did not include information on race. Prior commentary suggests that among explanatory predictors of crime, the most salient are environmental and socioeconomic factors rather than individual characteristics, such as race, and that the burden of FRHs and death is substantially greater among disadvantaged groups.
Fourth, the determination of psychiatric disorder was based on chart diagnosis using ICD-9 codes rather than chart review. It is possible that a fraction of patients with mental illness did not receive a diagnosis of psychiatric disorder in the hospital setting; therefore, our findings should not be interpreted as pertaining to all persons with mental illness.”
Overall, however, this study has been backed up by other evidence. For example, the University of Maryland Medical Center conducted a case-control study where it was found that:
“Prominent risk factors associated with recidivism were African American male, median age 31 years, unemployed, lacking medical insurance, annual income less than $10000, current drug user, past or present drug dealer, and a positive test for psychoactive substances on admission to the hospital. One hundred seventy-two (86%) of the cases felt that disrespect (called “dissing” in the local vernacular) was involved with their injury.”
This evidence all suggests that, when primary prevention of gun injuries and gun violence is not successful, installing a secondary prevention program in close proximity and working with a trauma unit at an urban hospital would be a very good step in preventing future gun violence. Something like a “full court press” on patients brought in for firearm-related injuries where they are offered help in changing the factors within them and around them that led to their victimization.
How exactly such a program would work, be funded, and be measured as being successful is for a different blog post at a later time.