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Temperature and firearm violence in four US cities: testing competing hypotheses

Introduction

Firearm violence is a major public health issue in the USA. There is growing evidence that firearm violence is associated with higher ambient temperatures. The aim of this study was to test competing hypotheses that could explain associations between temperature and firearm violence: temperature-aggression theory and routine activities theory.

Methods

We examined associations between elevated daily temperatures and shooting incidents in four US cities: Chicago, Illinois; Cincinnati, Ohio; New York, New York and Philadelphia, Pennsylvania. Temperature was operationalised using two different measures: daily maximum temperature and deviations of the daily maximum temperature from 30-year averages. Generalised linear autoregressive moving average models related temperature to shooting incidence while controlling for seasonal effects.

Results

As maximum daily temperature deviates from the expected, there was an association with increased shooting incidents in all four cities (eg, New York: b=0.014, 95% CI=0.011 to 0.017). An interaction term created by multiplying daily maximum temperature by the daily difference of maximum temperature from a 30-year average was also found to have a positive association in all four cities (eg, New York: b=0.020, 95% CI=0.016 to 0.025).

Discussion

These findings accord with previous studies demonstrating a positive relationship between temperature and firearm violence and further support temperature-aggression theory as the primary causal mechanism.

Fatal and non-fatal civilian injuries sustained during law enforcement-reported encounters in California, 2016-2021

Background

In 2015, California passed AB 71 to create a state-wide Use of Force Incident Reporting Database (URSUS) to tabulate law enforcement-reported encounters that resulted in serious bodily injury, death or discharge of a firearm. We use these data to analyse encounters that resulted in fatal and non-fatal civilian injuries in California between 2016 and 2021.

Methods

We performed a retrospective review of URSUS from January 2016 to December 2021. The main outcomes were the number of law enforcement encounters that involved civilian serious bodily injury or death and encounter-level characteristics.

Results

URSUS recorded 3677 incidents between 2016 and 2021 resulting in 942 civilian fatalities and 2735 instances of serious civilian injuries. Injury rates were highest for civilians who identified as Hispanic (1.80 injuries per 100 000 population) or black (5.17 injuries per 100 000 population). Injuries involving a firearm were usually fatal (58.9% fatality rate; 1471 injuries), while non-firearm incidents were more likely to result in serious injuries (4.2% fatality rate; 2929 injuries). We did not find statistically significant trends in rates of civilian injuries per 100 000 population.

Conclusion

Rates of law enforcement-related injuries were highest for Hispanic and black civilians in California between 2016 and 2021 and firearm-related injuries were overwhelmingly fatal. The URSUS database represents an important effort by law enforcement agencies to collect information on injuries and fatalities resulting from law enforcement encounters. Given similar databases exist in fewer than half of states, additional legislative efforts are needed to improve systematic national data collection on these encounters.

Firearm businesses as partners in suicide prevention: a cross-sectional study of the Gun Shop Project in Colorado, USA

Background

The Gun Shop Project aims to reduce firearm suicide and is widely implemented in the USA, yet little is known about the core firearm business practices and behaviours that might contribute to preventing firearm suicide.

Methods

Owners or managers of all firearm businesses identified as participants in Colorado’s Gun Shop Project were invited to respond to a questionnaire. Data collection occurred from March to May 2021. Analyses included unweighted descriptive statistics with CIs and Pearson 2 tests for categorical associations.

Results

54 firearm businesses participated (response rate: 28%). Under half reported practices that are Gun Shop Project core aspects (range: 14%–45%). 22% of businesses frequently engaged customers on the importance of safe firearm storage in suicide prevention while 26% had denied a firearm sale and 14% had assisted with temporary secure storage in the past year with customers perceived to be in suicidal crisis. However, high proportions reported willingness to engage in these behaviours if a customer was in crisis: 74% were willing to refuse a sale of a firearm or ammunition, 70% were willing to discuss temporary secure storage options and 70% were willing to direct customers to mental health services.

Conclusions

This study suggests that efforts to continue educating and involving firearm businesses may have an impact on the adoption of organisational suicide prevention practices and behaviours. Ongoing efforts are needed to understand core components of Gun Shop Project to inform standardised recommendations for effective firearm business practices that prevent firearm suicide.

Prediction of the mechanism of suicide among Minnesota residents using data from the Minnesota violent death reporting system (MNVDRS)

Background

Suicide remains a major public health problem, and firearms are used in approximately half of all such incidents. This study sought to predict the occurrence of suicide specifically by firearm, as opposed to any other means of suicide, in order to help inform possible life-saving interventions.

Methods

This study involved data from the Minnesota Violent Death Reporting System. Models evaluated whether data beyond basic demographics generated increased prediction accuracy. Models were built using random forests, logistic regression and data imputation. Models were evaluated for prediction accuracy using the area under the curve analysis and for proper calibration.

Results

Results showed that models constructed with social determinants and personal history data led to increased prediction accuracy in comparison to models constructed with basic demographic information only. The study identified an optimised ‘top 20’ variables model with a 73% chance of correctly discerning relative incident risk for a pair of individuals. Age, height/weight, employment industry/occupation, sex and education level were found to be most highly predictive of firearm suicide in the study’s ‘top 20’ model.

Conclusions

The study demonstrated that the use of a firearm in a death by suicide, as opposed to any other means of suicide, can be reasonably well predicted when an individual’s social determinants and personal history are considered. These predictive models could help inform many prevention strategies, such as safe storage practices, background checks for firearm purchases or red flag laws.

Trends in mortality after emergency department presentation for suicidal behaviour in California

Introduction

Emergency department patients presenting with non-fatal suicidal behaviour face elevated risk of suicide and all-cause mortality, but the extent to which this has changed over time is unknown. This study tracked trends in mortality risks faced by emergency department patients presenting with deliberate self-harm and suicidal ideation in California.

Methods

Using statewide linked emergency department and death data, we estimated 2010–2016 trends in suicide and all-cause mortality among emergency department patients with either deliberate self-harm (n=111 658) or suicidal ideation (n=162 959). We also calculated average annual percent changes in age-adjusted mortality rates and compared these to the general California population.

Results

Deliberate self-harm and suicidal ideation patients’ age-adjusted suicide rates decreased by approximately 5% per year during the study period; however, their all-cause mortality trends were flat. In the general California population, suicide rate trends were flat while all-cause mortality slightly declined.

Conclusions

Suicide mortality unexpectedly declined among self-harming and suicidal patients presenting to California emergency departments. Additional research is needed to understand the reasons behind this decline and inform quality improvement efforts for suicide prevention in hospital settings.