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Guns in the Home and Risk of a Violent Death in the Home: Findings from a National Study

Wednesday, 8th of June 2016

Guns in the Home and Risk of a Violent Death in the Home: Findings from a National Study

American Journal of Epidemiologyaje.oxfordjournals.org

Am. J. Epidemiol. (2004) 160 (10): 929-936. doi: 10.1093/aje/kwh309

Linda L. Dahlberg1,

Robin M. Ikeda2 and

Marcie-jo Kresnow3

- Author Affiliations

1 Division of Violence Prevention, National Center for Injury Prevention and Control, Centers for Disease Control and Prevention, Atlanta, GA.

2 Epidemiology Program Office, Centers for Disease Control and Prevention, Atlanta, GA.

3 Office of Statistics and Programming, National Center for Injury Prevention and Control, Centers for Disease Control and Prevention, Atlanta, GA.

 

Excerpts below; full text is at http://aje.oxfordjournals.org/content/160/10/929.full

Abstract

Data from a US mortality follow-back survey were analyzed to determine whether having a firearm in the home increases the risk of a violent death in the home and whether risk varies by storage practice, type of gun, or number of guns in the home. Those persons with guns in the home were at greater risk than those without guns in the home of dying from a homicide in the home (adjusted odds ratio = 1.9, 95% confidence interval: 1.1, 3.4). They were also at greater risk of dying from a firearm homicide, but risk varied by age and whether the person was living with others at the time of death. The risk of dying from a suicide in the home was greater for males in homes with guns than for males without guns in the home (adjusted odds ratio = 10.4, 95% confidence interval: 5.8, 18.9). Persons with guns in the home were also more likely to have died from suicide committed with a firearm than from one committed by using a different method (adjusted odds ratio = 31.1, 95% confidence interval: 19.5, 49.6). Results show that regardless of storage practice, type of gun, or number of firearms in the home, having a gun in the home was associated with an increased risk of firearm homicide and firearm suicide in the home.

Over 50,000 homicides and suicides occur each year in the United States (1), making them among the leading causes of death, particularly for young people. In 2001, homicide was the second leading cause of death and suicide the third for persons 15–24 years of age (2). Approximately 60 percent of all homicides and suicides in the United States are committed with a firearm (2).

Although an estimated 40 percent of adults in the United States report keeping a gun in the home for recreational or protective purposes (3), the risks and benefits of this practice are widely disputed in the literature (4, 5). Ecologic analyses have suggested a link between the prevalence of gun ownership and rates of homicide and suicide (6–8) and between regulations restricting access to firearms and rates of homicide and suicide (9–12). Although these studies are useful in demonstrating an association between access to firearms and rates of homicide and suicide at the aggregate level, it is not possible with this methodology to adequately assess whether access to a gun increases the risk of a violent death at the individual level.

To address these limitations, previous researchers have used case-control study methodology to evaluate the relation between gun ownership and risk of a violent death in the home. For example, Kellermann et al. (13, 14) examined the relation between gun ownership and injury outcomes. After they controlled for a number of potentially confounding factors, the presence of a gun in the home was associated with a nearly fivefold risk of suicide (adjusted odds ratio = 4.8) (13) and an almost threefold risk of homicide (adjusted odds ratio = 2.7) (14). Other case-control studies have also found an increased risk of suicide for those with firearms in the home, with relative risks ranging from 2.1 to 4.4 (15–19).

Some studies have specifically examined the association between purchase of a handgun and risk of a violent death (20, 21). In a case-control study of members of a large health maintenance organization, Cummings et al. (20) found that a history of family handgun purchase was associated with an elevated risk of both homicide and suicide. Wintemute et al. (21) reported similar findings for suicide in a population-based cohort study of persons who had purchased a handgun in California. In both studies, the effects persisted for more than 5 years. However, studies conducted in other countries have failed to find a clear link between access to a firearm and risk of a suicide (22).

Many of the studies conducted to date have been based on small samples and were limited to specific population groups such as adolescents or older adults (15–19). Most of the studies have also been limited to a few counties, geographic areas, or states. We know of only two national case-control studies that have examined the relation between access to a firearm and a violent death (23, 24). One study focused on the perpetration of homicide as opposed to victimization and found a relatively weak association (adjusted odds ratio = 1.4) between gun ownership and homicide perpetration (23). The other study focused on victimization and found a strong association for suicide (adjusted odds ratio = 3.4) but a weak association for homicide (adjusted odds ratio = 1.4) (24). In both studies, cases and controls were drawn from different data sources, and neither study was able to control for many of the potential confounders of homicide or suicide.

To evaluate the relation between firearms in the home and violent deaths in the home, we analyzed data from a US mortality follow-back survey. The purpose of our study was twofold: 1) to determine whether having a firearm in the home increases the risk of a homicide or suicide in the home relative to other causes of death in the home, and 2) to determine whether having a firearm in the home increases the risk that a homicide or suicide in the home will be committed with a firearm or by using other means. To our knowledge, this is the first national study to specifically examine the relation between firearms and violent deaths in the home.

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MATERIALS AND METHODS

Sample

Data for this study are from the 1993 National Mortality Followback Survey, which is based on a nationally representative 10 percent systematic sample of decedents aged 15 years or older in the United States (25). All 50 states with the exception of South Dakota, which was excluded because of a state law restricting the use of death certificates for research purposes, are represented in the National Mortality Followback Survey. The sample was drawn from death certificates received by the National Center for Health Statistics from state vital registration offices. To produce more reliable estimates, Blacks, persons less than 35 years of age or older than age 100 years, and persons who died from external causes of homicide, suicide, and unintentional injury were oversampled in this survey. The study protocol was reviewed and approved by the Centers for Disease Control and Prevention Institutional Review Board.

Data on each decedent in the National Mortality Followback Survey were obtained from death certificates and proxy-respondent interviews. All deaths were classified by using the International Classification of Diseases, Ninth Revision. The proxy interviews were conducted with next of kin or another person familiar with the decedent´s life history approximately 6 months from the date of death. The decedent´s next of kin, identified on the death certificate as having provided information, were initially contacted by letter and were asked to participate in the survey. In cases where no next-of-kin information was available from the death certificate, letters were sent to funeral directors requesting contact information for the next of kin. Over 90 percent of the proxy respondents were relatives, mostly immediate family members (spouse, parent, child, or sibling).

Interviews with the proxy respondents covered a wide range of topics including the decedent´s access to health care, daily activities, life events, alcohol consumption and tobacco and drug use, and history of problem behaviors. The interviews also included a number of questions on firearms in the home of the decedent. The overall response rate for the proxy respondent survey was 83 percent.

We used the death certificates for information on the decedent´s cause and manner of death and proxy-respondent interviews for all other demographic and behavioral information on the decedent. The study sample consisted of deaths that occurred in the home. Included were persons who subsequently died en route to or at a hospital. Deaths were classified by whether they were homicides (n = 490; International Classification of Diseases, Ninth Revision codes E960–E969), suicides (n = 1,049; International Classification of Diseases, Ninth Revision codes E950–E959), or the result of other causes (n = 535). Accidental poisonings or poisonings of undetermined intent, unintentional firearm injuries and firearm injuries of undetermined intent, and other deaths of undetermined cause were excluded from the study sample on the basis that they could be homicides or suicides. Deaths for which information on firearms in the home was missing were also excluded. By cause, these deaths were distributed similarly to those in the study sample. Overall, the study sample captured 89 percent of deaths for which the incident occurred in the home (n = 2,074/2,338).

Measures

Outcomes of interest

To determine whether having a firearm in the home increases the risk of a violent death in the home relative to other causes of death in the home, two outcome variables were created: 1) homicide versus other causes, and 2) suicide versus other causes. Violent deaths, whether from suicide or homicide, were excluded, respectively, from the “other causes of death” category. To determine whether having a firearm in the home increases the risk that a homicide or suicide will be committed with a firearm, we focused on homicides and suicides separately and created two additional outcome variables: 3) homicides committed with firearms versus homicides committed by using other methods, and 4) suicides committed with firearms versus suicides committed by using other methods.

Main exposure variable

The main exposure variable was the presence of a firearm in or around the home. Proxy respondents were asked, “At any time during the last year of life, were there any firearms kept in or around the home where the decedent stayed? Include those kept in a garage, outdoor storage area, truck, or car.” Responses were coded as follows: yes—one or more firearms were kept in or around the home; no—no firearms were kept in or around the home.

Refined measures of exposure

Proxy respondents were also asked how many guns were kept in or around the home; whether the firearms were handguns, shotguns, rifles, or other types of guns; and how the firearms were stored. Three refined measures of exposure were created: 1) number of guns (coded as one gun, two or more guns), 2) type of gun (coded as handguns only, long guns only, handguns and long guns), and 3) storage practice (coded as ≥1 gun unlocked, all guns locked).

Characteristics of the decedent

A number of demographic and behavioral characteristics identified in the literature as being associated with either homicide or suicide were included in the analysis. Included were age, sex, race/ethnicity, education, marital status, residential status (i.e., whether the decedent lived alone or with others), region of death, alcohol consumption within 4 hours of death, use and frequency of using illicit drugs (cocaine, crack cocaine, heroin, hallucinogens, amphetamines, marijuana or hashish) in the past year of life, and whether the decedent expressed a wish to die during the last month of life.

The suicide model also included whether the decedent had thoughts of attempting suicide within the last month of life and symptoms of depression and anxiety in the last month of life. Evidence of depression and anxiety was based on the mean score of responses to three or more of the following nine items: seemed worried or apprehensive, seemed drowsy or sluggish, seemed unresponsive or withdrawn, seemed impatient or annoyed, said things such as “I´m no good” or “I´m worthless,” cried for long periods of time for no apparent reason, slept more or less than usual, ate more or less than usual, and had trouble concentrating or making decisions. Mean scores ranged from 1 = never to 4 = often. The nine items are similar in wording and content to those used in existing scales of depression and anxiety but are not from a specific scale or index. Existing scales of depression and anxiety are designed for individual patient or respondent administration rather than proxy administration.

Analysis

We began with a bivariable analysis and calculated prevalence estimates for the characteristics of the decedent and the main exposure variable—presence of a firearm in or around the home. We then computed crude odds ratios and 95 percent confidence intervals to assess the association between each of the four outcome variables and the presence of a firearm in or around the home.

Next, we conducted a multivariable analysis by using logistic regression to examine the association between each of the four outcome variables and the main exposure variable, after adjusting for demographic and behavioral characteristics of the decedent. In modeling each outcome variable, we began with the main exposure variable, characteristics of the decedent (potential confounders), and all two-way interactions between the main exposure variable and characteristics of the decedent. Interactions were initially assessed simultaneously by using a likelihood ratio test and were then assessed individually in a backward stepwise fashion. The importance of interaction terms as well as main effects was assessed by using the Wald chi-square test statistic.

Finally, for models assessing whether the presence of a firearm in the home increases the risk that a homicide or suicide will be committed with a firearm, we performed a more refined analysis of exposure. We began with the final logistic regression model derived from the multivariable analysis and substituted our main exposure variable with the more refined measures of exposure (namely, type of gun, number of guns, and storage practice) to assess the association between certain firearm-related characteristics and each outcome.

All data were weighted to account for unequal selection probabilities and nonresponse and were poststratified to produce national estimates. Data were analyzed by using SUDAAN software (26) to account for the complex sampling design. p values of <0.05 were considered statistically significant.