The changing epidemiology of interpersonal firearm violence during the COVID-19 pandemic in Philadelphia, PA

Recent increases in firearm violence in U.S. cities are well-documented, however dynamic changes in the people, places and intensity of this public health threat during the COVID-19 pandemic are relatively unexplored. This descriptive epidemiologic study spanning from January 1, 2015 - March 31, 2021 utilizes the Philadelphia Police Department's registry of shooting victims, a database which includes all individuals shot and/or killed due to interpersonal firearm violence in the city of Philadelphia. We compared victim and event characteristics prior to the pandemic with those following implementation of pandemic containment measures. In this study, containment began on March 16, 2020, when non-essential businesses were ordered to close in Philadelphia. There were 331 (SE = 13.9) individuals shot/quarter pre-containment vs. 545 (SE = 66.4) individuals shot/quarter post-containment (p = 0.031). Post-containment, the proportion of women shot increased by 39% (95% CI: 1.21, 1.59), and the proportion of children shot increased by 17% (95% CI: 1.00, 1.35). Black women and children were more likely to be shot post-containment (RR 1.11, 95% CI: 1.02, 1.20 and RR 1.08, 95% CI: 1.03, 1.14, respectively). The proportion of mass shootings (≥4 individuals shot within 100 m within 1 h) increased by 53% post-containment (95% CI: 1.25, 1.88). Geographic analysis revealed relative increases in all shootings and mass shootings in specific city locations post-containment. The observed changes in firearm injury epidemiology following COVID-19 containment in Philadelphia demonstrate an intensification in firearm violence, which is increasingly impacting people who are likely made more vulnerable by existing social and structural disadvantage. These findings support existing knowledge about structural causes of interpersonal firearm violence and suggest structural solutions are required to address this public health threat.

Overflowing Disparities: Examining the Availability of Litter Bins in New York City

In the 1980s, activists' concerns about the disproportionate placements of landfills in low-income communities ignited the environmental justice movement. Today, similar issues of environmental injustice-the limited availability of litter bins across New York City (NYC) neighborhoods-remain unresolved. This study examines the association between NYC neighborhood income and litter bin availability. The NYC Department of Sanitation 2020 Litter Bin Inventory and archival measures of neighborhood composition and socioeconomic status were aggregated within NYC census tract neighborhoods. Multilevel Bayesian conditional autoregressive Poisson models estimated the prevalence rate ratio for counts of litter bins according to median household income in each census tract, accounting for spatial autocorrelation. Bivariate associations identified that census tracts with higher median household income had a greater prevalence of litter bins than census tracts with lower median household income; however, spatial autocorrelation attenuated the relationship between median household income and availability of litter bins. Further research is necessary to identify the spatially structured condition that accounted for the observed effect. The results warrant further investigation of both perceived and actual disparities in litter bin availability.

Mediating role of psychological distress in the associations between neighborhood social environments and sleep health

STUDY OBJECTIVES

The characteristics of neighborhood social environments, such as safety and social cohesion, have been examined as determinants of poor sleep. The current study investigates associations between neighborhood social characteristics and sleep health, as well as the mediating role of psychological distress on these possible associations.

METHODS

Three waves of PHRESH Zzz (n = 2699), a longitudinal study conducted in two low-income, predominately Black neighborhoods, were utilized for this analysis. The characteristics of neighborhood social environments were measured using crime rates, a neighborhood social disorder index, and self-reported social cohesion. Sleep health was measured via 7 days of wrist-worn actigraphy as insufficient sleep, sleep duration, wake after sleep onset (WASO), and sleep efficiency. G-estimations based on structural nested mean models and mediation analyses were performed to estimate the effects of neighborhood social environments on sleep as well as direct/indirect effects through psychological distress.

RESULTS

Crime rate around residential addresses was associated with increased risk of insufficient sleep (risk ratio: 1.05 [1.02, 1.12]), increased WASO (β: 3.73 [0.26, 6.04]), and decreased sleep efficiency (β: -0.54 [-0.91, -0.09]). Perceived social cohesion was associated with decreased risk of insufficient sleep (OR: 0.93 [0.88, 0.97]). Psychological distress mediated part of the associations of crime and social cohesion with insufficient sleep.

CONCLUSIONS

Neighborhood social environments may contribute to poor sleep health in low-income, predominantly Black neighborhoods, and psychological distress can be a salient pathway linking these neighborhood characteristics and sleep health.

Neighborhood Blighted Property Removal and 311 Calls for Non-Emergency Services: A Test of a Marker of Social Control

Many studies have demonstrated that collective efficacy is associated with positive health outcomes, lower crime, and violence in urban communities, and residents' emotional connection to their community. Remediation of blighted properties has been theoretically linked to increases in collective efficacy. The purpose of this study was to examine the impact of blighted property remediation on city non-emergency 311 calls for public incivilities and deterioration, as potential markers of collective efficacy. We used a quasi-experimental design to test whether 311 calls for service changed around remediated vacant lots in New Orleans, Louisiana, United States, many of which were left vacant after Hurricane Katrina in 2005. In six city neighborhoods eligible for blighted property remediation as part of a city program, 203 treated vacant lots were matched 1:3 without replacement to control lots that were eligible for but did not receive treatment. This yielded a total of 812 vacant lots partitioned within 48 months, or 38,976 lot-months. Controls were in the same New Orleans neighborhoods as their matched treatment lots but were at least 250 feet away to minimize contamination. Overall difference-in-differences models detected postintervention declines in calls related to dumping and garbage, and slight but mostly non-significant changes in calls between intervention and control lots in all but calls for dumping and vehicles. Blighted property remediation may have an impact on dumping and garbage, which is important. Despite being geographically specific, low-cost and longitudinal, the nature of 311 calls and structural and historic factors at play in both the concentration of vacant properties in communities and residents' willingness to call must be considered. Further analyses of changes in 311 data and additional qualitative inquiry are warranted to more fully determine the utility of these data.

Ridesharing and alcohol-related assaults in NYC: A spatial ecological case-crossover study

OBJECTIVE

Ridesharing has changed urban transportation and the distribution of some health outcomes, including alcohol consumption. Studies relating ridesharing to crime and violence at low space-time resolution (e.g., county-months) find mixed results. The aim of this study was to examine whether ridesharing was associated with increased incidence of alcohol-related assaults within highly resolved space-time units.

METHODS

This spatial ecological case-crossover study used rideshare and taxi trip data from the New York City (NYC) Taxi and Limousine Commission for 2017-2018 and assault data from the NYC Police Department, aggregated within taxi zone-hours. Conditional logistic regression models estimated the odds of observing an assault for case taxi zone-hours in which an assault occurred compared to two control units of the same taxi zone-hour one week before (-168 h) and one week after (+168 h) relative to the number of rideshare trips. Separate analyses assessed assaults occurring at bars and restaurants.

RESULTS

From 2017-2018, there were 47,124 nighttime assaults in the 262 taxi zones. There were 2482 taxi zone-hours at a bar and 693 taxi zone-hours at a restaurant that contained at least one nighttime assault. Ridesharing was positively associated with nighttime assaults at bars (OR: 1.050; 95% CI: 1.002-1.100) but not at restaurants (OR: 1.049; 95% CI: 0.943-1.168).

CONCLUSIONS

Additional ridesharing trips are associated with increased incidence of assaults at on-premise alcohol outlets in NYC at the precise hour and taxi zone of trip origins.

Stress and Distress during the COVID-19 Pandemic: The Role of Neighborhood Context

Neighborhoods play a central role in health and mental health, particularly during disasters and crises such as the COVID-19 pandemic. We examined changes in psychological distress following the pandemic, and the potential role of neighborhood conditions among 244 residents of New Orleans, Louisiana. Using modified linear regression models, we assessed associations between neighborhood characteristics and change in psychological distress from before to during the pandemic, testing effect modification by sex and social support. While higher density of offsite alcohol outlets (β = 0.89; 95% CI: 0.52, 1.23), assault rate (β = 0.14; 95% CI: 0.03, 0.24), and walkable streets (β = 0.05; 95% CI: 0.02, 0.07) in neighborhoods were associated with an increase in distress, access to neighborhood parks (β = −0.03; 95% CI: −0.05, −0.01), collective efficacy (β = −0.23; 95% CI: −0.35, −0.09), and homicide rate (β = −1.2; 95% CI: −1.8, −0.6) were associated with reduced distress related to the pandemic. These relationships were modified by sex and social support. Findings revealed the important but complicated relationship between psychological distress and neighborhood characteristics. While a deeper understanding of the neighborhoods’ role in distress is needed, interventions that target neighborhood environments to ameliorate or prevent the residents’ distress may be important not only during crisis situations.

Ride-Hailing and Road Traffic Crashes: A Critical Review

Ride-hailing businesses, including Uber and Lyft, have reshaped road traffic since they first began operating in the United States approximately a decade ago. It follows that ride-hailing may also alter the incidence and distribution of road traffic crash injuries and deaths. The available evidence relating ride-hailing to crashes is critically reviewed in this article. We present a theoretical model that synthesizes the hypothesized mechanisms, and we identify common methodological challenges and suggest priorities for future research. Mixed results have been reported for the overall incidence of road traffic crash injuries and deaths, likely due to heterogeneous impacts on vehicular traffic flow (e.g., increasing the volume of vehicles); on vehicle-, person-, and event-level characteristics (e.g., reducing alcohol-impaired driver crashes); on road-user types (e.g., increasing pedestrian crashes); and on environmental conditions (e.g., reducing crashes most substantially where public transit access is poorest). The lack of a well-developed theory of human mobility and methodological challenges that are common to many ecological studies impede exploration of these sources of moderation. Innovative solutions are required to explicate ride-hailing's heterogeneous impacts, to guide policy that can take advantage of the public health benefits of ride-hailing, and to ensure that research keeps pace with technological advances that continue to reshape road traffic use.

Place-based interventions and the epidemiology of violence prevention

Purpose of review

Violence is a leading cause of death, disability, and health inequity in the United States. This review summarizes the scientific literature on place-based interventions and violence, describes study design challenges, and suggests future directions for this group of interventions.

Recent findings

Violence prevention strategies commonly target high-risk individuals, but recent research has found that place-based interventions are practical, sustainable, and high-impact opportunities that benefit communities at large. This body of work has largely consisted of quasi-experimental studies of land and building place-based interventions and interpersonal violence.

Summary

Current epidemiological evidence suggests that place-based interventions are cost-effective solutions for violence prevention. Future work is needed using mixed methods to better understand their mechanisms of action and to inform implementation efforts. There are opportunities for the broader development of implementation science to bring promising and established place-based interventions to scale and to extend these interventions to other types of violence.

Rideshare Trips and Alcohol-Involved Motor Vehicle Crashes in Chicago

OBJECTIVE

Rideshare companies such as Uber and Lyft have substantially changed transportation markets in the United States and globally. The aim of this study was to examine whether ridesharing is associated with reductions in alcohol-involved crashes.

METHOD

This case-series study used highly spatially and temporally resolved trip-level rideshare data and motor vehicle crash data from the Chicago Data Portal from November 2018 to December 2019. The units of analysis were motor vehicle crashes in Chicago. Events of interest were 962 crashes that police indicated were alcohol involved. The comparison group was 962 non-alcohol-involved crashes that occurred in the same census tract, matched 1:1. The exposure of interest was the density per square mile of rideshare trips that were in progress at the time of the crash, calculated using a kernel density function around the estimated route paths of active trips. A conditional logistic regression compared alcohol involvement to rideshare trip density while adjusting for matching and relevant time-varying covariates (taxi trips, precipitation, temperature, holidays).

RESULTS

Mean rideshare trip density was 69.0 per square mile (SD = 129.7) at the time and location of alcohol-involved crashes and 105.7 per square mile (SD = 192.6) at the time and location of non-alcohol-involved crashes. After controlling for covariates, the conditional logistic regression model identified that a standard deviation increase in rideshare trips per square mile at the crash location was associated with 23% decreased odds that the crash location was alcohol involved (odds ratio = 0.771; 95% confidence interval [0.594, 0.878]).

CONCLUSIONS

Ridesharing may replace motor vehicle trips by alcohol-impaired drivers.

The geographic distribution of retail tobacco outlets in Yogyakarta, Indonesia

INTRODUCTION

Tobacco smoking prevalence in Indonesia is among the highest in the world. Research worldwide identifies that physical access to tobacco through retail outlets is related to increased tobacco smoking. Tobacco outlet density is very high in many Indonesian cities, so tobacco access may contribute to the high prevalence of tobacco use in that country. The aim of this study was to examine distributions of tobacco outlets in one Indonesian city, Yogyakarta, in relation to social and physical environmental conditions.

METHODS

For this cross-sectional ecological study, we virtually audited randomly selected street segments (n = 1099) using Google Street View. The outcome of interest was a count of tobacco advertising banners (indicating the presence of retail outlets). Exposures were physical environmental conditions (scales of main roads, physical decay, presence of schools, mosques, churches) and social conditions measured at the neighbourhood level (concentrated disadvantage, age composition, population density).

RESULTS

Tobacco banners were present on 36.4% of sampled street segments, including 55 (37%) of 147 streets with schools; a total of 1381 banners were identified. Multilevel negative binomial regression models for street segments nested within neighbourhoods found the prevalence of tobacco banners per 100 m was lower near schools (RR = 0.66, 95% CI 0.45, 0.97) and was not associated with other exposure measures.

DISCUSSION AND CONCLUSIONS

Retail tobacco outlets are ubiquitous in Yogyakarta. Although they are relatively less prevalent on streets with schools, the high absolute values and wide spatial distribution means all residents of Yogyakarta are exposed to tobacco outlets.

Changes in Shooting Incidence in Philadelphia, Pennsylvania, Between March and November 2020

This study uses police department registry data to describe trends in incidence of firearm shootings and deaths in January-November 2020, before and after the closure of nonessential businesses in March, the killing of George Floyd in May, and the partial lifting of containment policies in June.

Trends in US Alcohol Consumption Frequency During the First Wave of the SARS-CoV-2 Pandemic

Background

The SARS‐CoV‐2 pandemic created disruptions and stressors which may have influenced alcohol consumption frequency trends. Varying COVID‐19 health burden and alcohol policies may have contributed to different consumption trends between states. The aim of this study is to assess trends in alcohol consumption and moderation by state of residence.

Methods

We examined trends in adult drinking days, during the first wave of the pandemic (March 10 to June 8) using longitudinal data from the Understanding America Study (N = 6,172 unique participants; N = 28,059 observations). Because state mandates were responsive to disease burden, we modeled the interaction of time by COVID‐19 burden, defined as whether the state had the median (or higher) daily incidence of COVID‐19 cases on the survey date, and state random effects. We controlled for individual sociodemographics, perceived personal/familial COVID‐19 burden, mental health symptomology, and risk avoidance.

Results

Drinking days increased throughout the duration (incidence risk ratio [IRR] for drinking per increase in one calendar day = 1.003, 95% CI 1.001, 1.004); trends were heterogeneous by disease burden, with individuals living in states with lower COVID‐19 burden increasing (IRR = 1.005, 95% CI 1.003, 1.007) faster than those living in states with higher COVID‐19 burden (IRR = 1.000, 95% CI 0.998, 1.002). Trends were heterogeneous between states, but there was no evidence of systematic geographic clustering of state trends.

Conclusions

Drinking days increased during the first months of the COVID‐19 pandemic, particularly among residents of states with lower disease burden.

Alcohol-involved motor vehicle crashes and the size and duration of random breath testing checkpoints

OBJECTIVE

Sobriety checkpoints have strong empirical and theoretical support as an intervention to reduce alcohol-involved motor vehicle crashes. The purpose of this study was to examine whether checkpoint size (the number of police officers) and checkpoint duration (the amount of time in operation) affect associations between individual checkpoints and subsequent alcohol-related crash incidence.

METHOD

Queensland Police Service provided latitude-longitude coordinates and date and time data for all breath tests that occurred in Brisbane, Australia, from January 2012 to June 2018. We applied hierarchical cluster analysis to the latitude-longitude coordinates for breath tests, identifying checkpoints as clusters of ≥25 breath tests conducted by ≥3 breath testing devices over a duration of 3 to 8 hours. Generalized linear autoregressive moving average (GLARMA) models related counts of alcohol-involved motor vehicle crashes to the number of checkpoints conducted per week, as well as 1 week prior and 2 weeks prior.

RESULTS

A total of 3420 alcohol-related crashes occurred and 2069 checkpoints were conducted in Brisbane over the 6.5-year (339-week) study period. On average, checkpoints included a mean of 266.0 breath tests (SD = 216.3), 16.4 devices (SD = 13.7), and were 286.3 minutes in duration (SD = 104.2). Each 10 additional checkpoints were associated with a 12% decrease in crash incidence at a lag of 1 week (IRR = 0.88; 95%CI: 0.80, 0.97). We detected no differential associations according to checkpoint size or duration.

CONCLUSIONS

Sobriety checkpoints are associated with fewer alcohol-related motor vehicle crashes for around 1 week. Checkpoint size and duration do not appear to affect this relationship.

Epidemiologic Trends in Fatal and Nonfatal Firearm Injuries in the US, 2009-2017

IMPORTANCE

Firearm injury research in the US has focused on fatal injuries. The incidence and epidemiologic factors associated with nonfatal firearm injuries are less understood.

OBJECTIVE

To evaluate estimates of incidence and trends over time of fatal and nonfatal firearm injuries.

DESIGN, SETTING, AND PARTICIPANTS

A cross-sectional, ecologic study was conducted using data throughout the US from 2009 to 2017. Data on fatal injuries from the Centers for Disease Control and Prevention were combined with national data on emergency department visits for nonfatal firearm injury from the Nationwide Emergency Department (ED) sample. Data analysis was conducted from August 2019 to September 2020.

EXPOSURES

Firearm injuries identified with International Classification of Diseases external cause of injury codes and categorized by intent of injury, age group, and urban-rural location.

MAIN OUTCOMES AND MEASURES

Incidence, case fatality rate, and trends over time of firearm injury according to intent, age group, and urban-rural location.

RESULTS

From 2009 to 2017, there was a mean of 85 694 ED visits for nonfatal firearm injury and 34 538 deaths each year. An annual mean of 26 445 deaths (76.6%) occurred outside of the hospital. Assault was the most common overall mechanism (38.9%), followed by unintentional injuries (36.9%) and intentional self-harm (19.6%). Self-harm, which accounted for 21 128 deaths (61.2%), had the highest case fatality rate (89.4%; 95% CI, 88.5%-90.4%), followed by assault (25.9%; 95% CI, 23.7%-28.6%) and legal intervention (23.4%; 95% CI, 21.6%-25.5%). Unintentional injuries were the most common nonfatal injuries (43 729 [51.0%]) and had the lowest case fatality rate (1.2%; 95% CI, 1.1%-1.3%). Self-harm deaths, 87.8% of which occurred outside the hospital, increased in all age groups in both rural and urban areas during the study period and were most common among people aged 55 years and older. The rate of fatal assault injuries was higher in urban than in rural areas (16.6 vs 9.0 per 100 000 per year) and highest among people aged 15 to 34 years (38.6 per 100 000 per year). Rates of unintentional injury were higher in rural than in urban areas (18.5 per 100 000 vs 12.4 per 100 000).

CONCLUSIONS AND RELEVANCE

In this cross-sectional study, suicide appears to be the most common cause of firearm injury death in the US, and most people who die from suicide never reach the hospital. These findings suggest that assaults and unintentional injuries account for most nonfatal and overall firearm injuries and for most of the injuries that are treated in hospitals.

A comparison and analysis of seven gun law permissiveness scales

BACKGROUND

Due to the differences in the way gun law permissiveness scales were created and speculation about the politically motivated underpinnings of the various scales, there have been questions about their reliability.

METHODS

We compared seven gun law permissiveness scales, varying by type and sources, for an enhanced understanding of the extent to which choice of a gun law permissiveness scale could affect studies related to gun violence outcomes in the United States. Specifically, we evaluated seven different scales: two rankings, two counts, and three scores, arising from a range of sources. We calculated Spearman correlation coefficients for each pair of scales compared. Cronbach's standardized alpha and Guttman's lambda were calculated to evaluate the relative reliability of the scales, and we re-calculated Cronbach's alpha after systematically omitting each scale to assess whether the omitted scale contributed to lower internal consistency between scales. Factor analysis was used to determine single factor loadings and estimates. We also assessed associations between permissiveness of gun laws and total firearm deaths and suicides in multivariable regression analyses.

RESULTS

All pairs of scales were highly correlated (average Spearman's correlation coefficient r = 0.77) and had high relative reliability (Cronbach's alpha = 0.968, Guttman's lambda = 0.975). All scales load onto a single factor. The choice of scale did not meaningfully change the parameter estimates for the associations between permissiveness of gun laws and gun deaths and suicides.

CONCLUSION

Gun law permissiveness scales are highly correlated despite any perceived political agenda, and the choice of gun law permissiveness scale has little effect on study conclusions related to gun violence outcomes.

The feasibility and acceptability of mobile health monitoring for real-time assessment of traumatic injury outcomes

BACKGROUND

Traumatic injuries are a health event that can begin a trajectory towards chronic health and social challenges. Mobile technology-based prevention and treatment interventions have been used to monitor and transform outcomes across a myriad of health conditions, but their potential in long-term injury recovery is unexplored. The goal of this pilot study was to assess the acceptability and feasibility of mobile health monitoring for long-term outcomes in a population of trauma patients with known barriers to health and social care after injury.

METHODS

We re-recruited 25 individuals, 12-36 months after acute hospitalization, from a recently concluded study of psychological outcomes in seriously injured Black men in Philadelphia, Pennsylvania. This mixed- methods pilot study was conducted in three phases: (I) qualitative interviews and development of a pilot monitoring platform; (II) a 3-month feasibility trial of mobile monitoring of patient-reported outcomes and biometric data using a wrist-worn commercial fitness monitor (n=18); (III) post-implementation qualitative interviews.

RESULTS

Analysis of data from pre-implementation interviews indicated that the majority of participants used smartphones as a primary means of communicating with their social network and to access the internet. The 90-day pilot trial of mobile monitoring indicated participants' preference text-delivered communication and survey elicitation. Response rates for 12 automated surveys ranged from 84-92%. Twenty-four hours a day adherence to optional biometric monitoring was generally lower than 50% but ranged widely indicating both very low adherence and very high adherence. Four of 25 participants, 2 who had opted for Fitbit monitoring, were lost to follow-up at the end of the 90-day pilot trial. In post-implementation assessments, participants endorsed the acceptability of mobile monitoring highlighting the benefit of its convenience and flexibility over in-person outcome monitoring. Participants also perceived its potential benefit in long-term engagement with health and social services to assist with the challenges they faced when attempting to achieve physical, psychological, social, and financial recovery after hospitalization. These findings were reinforced through qualitative interviews which highlighted, in addition to acceptability, the perceived value of self-monitoring through the use of wearable devices to track health data like physical activity and sleep.

CONCLUSIONS

This study indicates the feasibility and acceptability of mobile health monitoring used to examine long-term injury sequalae. Future research may leverage this novel strategy, refining its application to address current limitations in the reliability and accuracy of commercially available wearable technology, relative costs and benefits of different mobile data collection strategies, integration within current clinical paradigms and generalizability across injured populations and socio-ecological environments.

Firearm Homicide Incidence, Within-state Firearm Laws, and Interstate Firearm Laws in US Counties

BACKGROUND

Firearm homicides occur less frequently in US states with more firearm control laws. However, firearms are easily transported across state lines, and laws in one location may affect firearm violence in another. This study examined associations between within-state firearm laws and firearm homicide while accounting for interference from laws in other nearby states.

METHODS

The units of analysis were 3,107 counties in the 48 contiguous US states, arrayed in 15 yearly panels for 2000 to 2014 (n = 46,605). The dependent measure was firearm homicides accessed from the Centers for Disease Control and Prevention (CDC) Compressed Mortality Data. The main independent measures were counts of firearm laws and the proportion of laws within categories (e.g., background checks, child access prevention laws). We calculated these measures for interstate laws using a geographic gravity function between county centroids. Bayesian conditional autoregressive Poisson models related within-state firearm laws and interstate firearm laws to firearm homicides.

RESULTS

There were 172,726 firearm homicides in the included counties over the 15 years. States had between 3 and 100 firearm laws. Within-state firearm laws (incidence rate ratio [IRR] = 0.995, 95% confidence interval [CI] = 0.992, 0.997) and interstate firearm laws (IRR = 0.993, 95% CI = 0.990, 0.996) were independently associated with fewer firearm homicides, and associations for within-state laws were strongest where interstate laws were weakest.

CONCLUSIONS

Additional firearm laws are associated with fewer firearm homicides both within the states where the laws are enacted and elsewhere in the United States. Interference from interstate firearm laws may bias associations for studies of within-state laws and firearm homicide.

The unknown denominator problem in population studies of disease frequency

Problems related to unknown or imprecisely measured populations at risk are common in epidemiologic studies of disease frequency. The size of the population at risk is typically conceptualized as a denominator to be used in combination with a count of disease cases (a numerator) to calculate incidence or prevalence. However, the size of the population at risk can take other epidemiologic properties in relation to an exposure of interest and the count outcome, including confounding, modification, and mediation. Using spatial ecological studies of injury incidence as an example, we identify and evaluate five approaches that researchers have used to address "unknown denominator problems": ignoring, controlling for a proxy, approximating, controlling by study design, and measuring the population at risk. We present a case example and recommendations for selecting a solution given the data and the hypothesized relationship between an exposure of interest, a count outcome, and the population at risk.

The association between blighted property remediation and domestic crime by alcohol availability

There is increasing evidence that place-based interventions reduce crime and interpersonal violence in urban settings. However, evidence concerning the impacts of these neighborhood interventions on domestic crime (crime between intimate partners, family, or household members) is inconclusive. We used data from a New Orleans, Louisiana, place-based blighted property remediation intervention to test the hypothesis that the intervention was associated with changes in domestic crime. Because there is evidence that alcohol availability is related to domestic crime, we also assessed whether this association was moderated by alcohol outlet density. We assessed overall associations using a difference-in-difference approach and assessed moderation using a triple-difference approach. The analytic sample consisted of 204 remediated lots and 612 non-remediated matched control lots over 84 months (2011-2017), for a total of 68,544 lot-months. In difference-in-differences analyses, the place-based intervention was associated with additional domestic crime incidence (β = 0.311, 95% CI: 0.016, 0.605; p = 0.039). In triple-difference analyses, on-premise bar density modified this association (β = -0.119, 95%CI: -0.147, -0.092; p < 0.001): in areas with higher bar density, increases in domestic crime were lower near remediated lots compared with control lots. Place-based interventions to reduce blighted properties may have contributed to fewer domestic crime incidents in areas with more bars.

Alcohol Industry vs. Public Health Presentations at Judicial Reviews of Liquor Licence Applications in Australia

Greater densities of alcohol outlets are associated with greater incidence of alcohol-related harms. In Australia, public health advocates aiming to limit alcohol availability expend significant energy objecting to new outlets in licensing and planning hearings. This study identifies and reviews the key scientific arguments put forward by industry and public health representatives in liquor and planning hearings to determine the factors that contribute to decisions by the presiding authority and to identify ways forward for researchers wishing to facilitate harm minimisation through these regulatory forums. Scientific evidence presented in 23 cases from Victoria, New South Wales and Western Australia between 2010 and 2018 were assessed using directed content analysis. Cases were identified through the AustLii and Westlaw online databases. The full transcripts of two cases that were identified as representative of the scientific arguments presented in other included cases were also reviewed. Four main arguments that industry used during hearings were identified-causal inference, non-linearities, differentiation and risk mitigation. These arguments were used across many included hearings and raised fundamental questions that public health evidence was often ill-equipped to respond to. The overall success of industry arguments in liquor and planning hearings highlighted the challenges of applying epidemiological evidence to individual case studies. These findings have particular implications and will be of use for researchers and public health experts participating in future licensing hearings, especially those wishing to prevent alcohol-related harm through regulatory mechanisms such as state licensing authorities (i.e. courts).

Firearm laws and illegal firearm flow between US states

BACKGROUND

Considerable variation in firearm legislation exists. Prior studies show an association between stronger state laws and fewer firearm deaths. We hypothesized that firearms would flow from states with weaker laws to states with stronger laws based on proximity and population.

METHODS

Crime gun trace data from 2015 to 2017 was accessed from the Bureau of Alcohol, Tobacco, Firearms and Explosives and compared with the count and composition of firearm legislation in 2015 among the contiguous 48 states. Additional independent variables included population, median household income, distance, and presence or absence of a shared border. We used Exponential Random Graph Models to identify predictors of traced firearm transfers between origin and destination states.

RESULTS

After controlling for network structure, firearm laws in origin states were associated with fewer traced firearm transfers (incidence rate ratio [IRR], 0.88; 95% confidence interval [CI], 0.83-0.93; p < 0.001). Conversely, more firearm laws in destination states were associated with more traced firearm transfers (IRR, 1.10; 95% CI, 1.06-1.15; p < 0.001). Larger population at the origin was associated with increased transfers (IRR, 1.38; 95%CI, 1.27-1.50; p < 0.001), as was larger population at the destination state (IRR, 1.45; 95% CI, 1.35-1.56; p < 0.001). Greater distance was associated with fewer transfers (for each 1,000 km; IRR, 0.35; 95% CI, 0.27-0.46; p < 0.001), and transfers were greater between adjacent states (IRR, 2.49; 95% CI, 1.90-3.27; p < 0.001).

CONCLUSION

State firearm legislation has a significant impact on gun trafficking even after controlling for network structure. States with stricter firearm legislation are negatively impacted by states with weaker regulations, as crime guns flow from out-of-state.

LEVEL OF EVIDENCE

Epidemiologic, level III.

Ridesharing and motor vehicle crashes: a spatial ecological case-crossover study of trip-level data

BACKGROUND

Ridesharing services (eg, Uber, Lyft) have facilitated over 11 billion trips worldwide since operations began in 2010, but the impacts of ridesharing on motor vehicle injury crashes are largely unknown.

- METHODS

This spatial ecological case-cross over used highly spatially and temporally resolved trip-level rideshare data and incident-level injury crash data for New York City (NYC) for 2017 and 2018. The space-time units of analysis were NYC taxi zone polygons partitioned into hours. For each taxi zone-hour we calculated counts of rideshare trip origins and rideshare trip destinations. Case units were taxi zone-hours in which any motor vehicle injury crash occurred, and matched control units were the same taxi zone from 1 week before (-168 hours) and 1 week after (+168 hours) the case unit. Conditional logistic regression models estimated the odds of observing a crash (separated into all injury crashes, motorist injury crashes, pedestrian injury crashes, cyclist injury crashes) relative to rideshare trip counts. Models controlled for taxi trips and other theoretically relevant covariates (eg, precipitation, holidays).

RESULTS

Each additional 100 rideshare trips originating within a taxi zone-hour was associated with 4.6% increased odds of observing any injury crash compared with the control taxi zone-hours (OR=1.046; 95% CI 1.032 to 1.060). Associations were detected for motorist injury and pedestrian injury crashes, but not cyclist injury crashes. Findings were substantively similar for analyses conducted using trip destinations as the exposure of interest.

CONCLUSIONS

Ridesharing contributes to increased injury burden due to motor vehicle crashes, particularly for motorist and pedestrian injury crashes at trip nodes.