Firearm-Related Hospitalization and Risk for Subsequent Violent Injury, Death, or Crime Perpetration

Editors' Notes Context Understanding the risks faced by patients after a firearm-related hospitalization (FRH) may help efforts to prevent further injury and improve outcomes. Contribution This statewide-study found that after a FRH, patients were at markedly elevated risks for recurrent FRH, firearm-related death, and firearm- or violence-related arrest. Implication Identification of variables associated with the risk for subsequent adverse outcomes may help guide inter-ventions at the time of FRH. Seventy percent of homicides and 10% of nonfatal violent crimes in the United States are related to firearms (13). There are 40 times as many nonfatal firearm-related crimes as there are firearm-related deaths, and 23% of victims of such crimes sustain an injury (3). Of those with nonfatal firearm-related injuries who receive medical attention in the emergency department, an estimated 30% to 60% are hospitalized, depending on the injury intent (4). Overall, firearm-related hospitalizations (FRHs) are associated with substantial physical and psychological morbidity as well as societal cost (57). Information on the risk for subsequent violent victimization (that is, becoming a victim) or crime perpetration after an FRH is lacking. Such information must be obtained to inform the need for future interventions among this group of patients. For example, interventions, such as brief motivational interviewing, conducted among trauma patients during their hospitalization have been shown to reduce rates of posttraumatic stress and alcohol use disorders as well as trauma and violent behavior recidivism while improving functional recovery (810). An enhanced understanding of the subsequent risk for violent injury, death, or crime perpetration may help frontline health care providers, public health professionals, criminal justice officials, and policymakers devise and implement integrated risk assessment plans and harm reduction strategies at the time of hospitalization and after discharge among patients with an FRH. We conducted a statewide epidemiologic investigation to determine the absolute rates of subsequent violent injury, death, or crime perpetration after discharge among patients with an FRH, and to compare these rates with those of 2 comparison groups comprising patients hospitalized for noninjury reasons and the general population. Our hypothesis was that patients with an FRH were at highest risk for violent injury, death, or crime perpetration after discharge. Methods Overview of Study Design We used a retrospective cohort study design. First, using codes from the International Classification of Diseases, Ninth Revision (ICD-9), we identified all trauma patients hospitalized in 2006 to 2007 in Washington. Each patient's first hospitalization during these years was defined as their index hospitalization. We chose 2 comparison groups: a random sample of patients with a noninjury-related index hospitalization frequency matched with the injury group on age and year of hospitalization, and the general population of Washington. Information on outcomes was collected through 31 December 2011. The Human Subject Division of the Washington State Department of Health approved the study protocol and procedures. Exposures Consistent with prior literature, an injury-related hospitalization was defined as a hospital discharge with a primary diagnosis of an acute injury (ICD-9 codes 800 to 959). Using codes for external causes of injury (E codes), we excluded records for the following mechanisms: injuries from medical and surgical misadventures (E870 to E879), late effects of injury (E929 or E999), and adverse effects of substances in therapeutic use (E930 to E949) (11). Information on index hospitalization was obtained by using the Washington State Comprehensive Hospital Abstract Reporting System (CHARS) (12), which contains coded hospital inpatient discharge information and is used to collect an array of data elements, such as age, sex, payer status, and codes for diagnoses and procedures. Using ICD-9 and E codes, we categorized index hospitalizations into the following distinct subgroups: violent injury, which was further divided into firearm-related (of any intent [assault, self-inflicted, unintentional, or undetermined]) and nonfirearm-related (assault or self-inflicted) injuries; nonviolent injury; and noninjury. We used the definition of a violent death from the National Violent Death Reporting System (NVDRS) (an injury resulting either from the intentional use of physical force or power against oneself, another person, or a group or community [13]) as a guide to define violent injury in this investigation. Consistent with NVDRS practice, we included firearm injuries of any intent in the subgroup of violent injury. The primary exposure was index FRH. Secondary exposures included index hospitalization related to nonfirearm violence and hospitalization for a nonviolent injury. Index noninjury hospitalization served as the reference category. Outcomes Outcomes measured after index hospitalization discharge were subsequent violence-related hospitalization, death, or arrest. Statewide records on all hospitalizations, deaths, and arrests from 2006 through 2011 were obtained from CHARS, the Washington State Department of Health, and the Washington State Patrol, respectively. Subsequent injury-related hospitalizations and deaths were classified with the same categorization scheme used for index hospitalization. We used specific codes in the Revised Code of Washington to classify arrests as due to a firearm-related or violent crime or a nonfirearm nonviolent crime. Because the Revised Code of Washington does not typically distinguish between violent crimes that involve firearms and those that do not, we grouped firearm-related crimes (such as theft) and violent crimes (regardless of whether a firearm was involved) into 1 class (firearm- or violence-related arrest), as recommended by previous investigators who faced this methodological limitation (14). We used the definition of a violent crime used by the Uniform Crime Reporting program of the Federal Bureau of Investigation (an offense that involves force or threat of force, including criminal homicide, forcible rape, robbery, and aggravated assault [15]) as a guide to define a violent crime. Primary outcomes included subsequent FRH, firearm-related death, and the combined outcome of firearm- or violence-related arrest. Secondary outcomes included subsequent hospitalization for a nonfirearm violent injury, nonfirearm violent death, and arrest for a nonfirearm nonviolent crime. Covariates Information on age, sex, payer status, year and season of discharge, and county of the hospital for index hospitalization was captured. We also sought to examine the association of history of a diagnosis of psychiatric disorder, arrest, and conviction with the aforementioned outcomes. For this purpose, statewide records on all hospitalizations, arrests, and convictions from 2001 through 2005 were obtained from CHARS, the Washington State Patrol, and the Administrative Office of the Courts Judicial Information System, respectively. Figure 1 provides a pictorial representation of the overall study design. Figure 1. Pictorial representation of study design. Statistical Analysis Probabilistic algorithms were used to link each patient's index hospitalization record to their hospitalization, vital status, arrest, and conviction records. A subset of identifiers, including first 2 letters of the first name, first 2 letters of the last name, date of birth, sex, and first 3 digits of ZIP code of residence, was used for the linkage. The analytic database was restricted to matches with an accuracy likelihood of at least 99% (Appendix). Follow-up began on the day of index hospitalization discharge and ended on the day of the subsequent event (first hospitalization, death, or first arrest, each in its corresponding analysis) or on 31 December 2011, whichever occurred first. For the analysis of subsequent hospitalization, follow-up began 90 days after index hospitalization discharge to minimize potential misclassification of readmissions for index injury as new recurrent injury events. In a sensitivity analysis, we used a 180-day period after index hospitalization discharge. We conducted an additional sensitivity analysis in which the follow-up time for subsequent arrest began 1 day after index hospitalization discharge to minimize potential misclassification of arrests for index injury as new criminal events. We calculated the incidence rate of each outcome by type of index hospitalization. The cumulative incidence of a subsequent event for each type of index hospitalization was estimated by using the unadjusted cumulative incidence function, with death treated as a competing event for hospitalization and arrest, and other-cause mortality treated as a competing event for firearm-related mortality. In regression analyses, we used the methods described by Fine and Gray (16) to model each outcome with the subdistribution hazards regression, with death treated as a competing event for hospitalization and arrest, and other-cause mortality treated as a competing event for firearm-related mortality. Subhazard ratios (sHRs) and their corresponding CIs were determined by using models that included variables for age, sex, payer status, county of the hospital, discharge year and season, history and type of arrest, and history and type of psychiatric disorder diagnosis. In a sensitivity analysis, history of crime was represented as a combination of arrest and conviction records (convicted, arrested but not convicted, or not arrested). Using the age and sex distribution of the 2000 U.S. Census population, we calculated standardized incidence and mortality ratios to compare the risk for a subsequent FRH and death between patients with an index FRH and persons in the general population of Washington. An level of 0.05 was used to