Topography of Trauma in Arizona

Abstract

Background: Traumatic injuries lead all other causes of death for Americans 1-44 years old. In Arizona (AZ), 46,842 patients were treated for traumatic injuries, of whom 1,111 (2.4%) people (75 per 100,000 population) died in 2016. Traumatic injuries and the places where they occur have been studied in both urban and rural settings. The associations of geography and traumatic injury, specifically, areal socioeconomic deprivation and alcohol outlets and their associations with trauma events and the subset of traumas arising from assaults in AZ have not been evaluated. This study sought to examine the geographic clustering of these events, and their respective associations with published areal risk factors in AZ. We hypothesized that, 1. the occurrences of trauma and assaultive trauma are highly clustered as discrete events and as events per census block group, 2. the number of alcohol outlets in an area and socioeconomic deprivation are positively associated with the geographic locations where the assault-related traumas occur. Methods: A retrospective, ecological study was performed incorporating data from multiple sources at the state and national levels. Trauma cases were provided by the Arizona Department of Health Services State Trauma Registry. Each case included data related to the mechanism and intent of injury as well as diagnoses of each patient’s list of injuries. Trauma events were aggregated to their respective census block group areas. Data for retail alcohol availability and socioeconomic deprivation came from state and national published data. Socioeconomic deprivation was characterized via the area deprivation index (ADI) that used 17 variables from the United States Census to quantify socioeconomic indicators at the census block group level. The index was standardized to a mean of 100 and standard deviation of 20. Higher ADI values represent greater deprivation for a given location. The addresses of bars and retail alcohol outlets for offsite consumption were geocoded and aggregated by census block group. Population density was measured as persons per square mile. The geographic clustering of trauma was evaluated as discrete events using the Average Nearest Neighbor distance method (ANN). Global spatial autocorrelation of population density, ADI, traumas and assaultive traumas per block group were evaluated using Moran’s I statistic. Traumas and assaults per block group were evaluated for spatial autocorrelation and mapped by the Anselin’s Local Indicators of Spatial Autocorrelation (LISA) to identify clusters and outliers. The associations of alcohol outlets per block group, ADI, population density and traumas including assaults per block group were quantified with geographically weighted regression (GWR) models. Results: After approval by the human subjects review boards of the University of Arizona and the AZ Department of Health Services, data for 177,311 trauma patients including 4,575 (2.6%) deaths for the years 2013-2017 were analyzed. Traumas in AZ were highly clustered as discrete events (ANN z-statistic = -799, p<0.001) and 2,370 statistically significant clusters and outliers among the 4,178 block groups in AZ were identified. When the attribute of traumas per block group was evaluated using Moran’s I, population density (Index 0.5, p<0.001), ADI (0.60, p=0.01), and alcohol outlets (0.21, p<0.001) also demonstrated significant clustering across AZ. Three hundred and three block groups were identified as part of statistically significant clusters or outliers. Traumas per block group demonstrated one high-value cluster, seven low-value cluster, and 295 outlier high or low value block groups. There were 14,998 cases due to assault including 574 (3.8%) patients who died from their injuries. Moran’s I statistic indicated the spatial distribution for assaults per block group are neither spatially clustered nor dispersed (-0.004, p=0.71), although Anselin’s LISA demonstrated 11 high value clusters, 101 low value clusters, 338 outlier block groups, all with p-values <0.05. GWR demonstrated a significant association of trauma events with alcohol retail outlets for offsite consumption, (coefficient (coeff) 9.98, standard deviation (sd) 1.879). ADI (coeff. 0.32, sd 0.09) and population density per block group (coeff. -0.003, sd 0.0005). Thus, adjusting for socioeconomic deprivation and population density, the presence of alcohol outlets in the block group increased the likelihood of traumas resulting in injury. Assault-related traumatic injury was associated with the number of alcohol retail outlets (coeff. 0.95, sd 0.07) and ADI (coeff. 0.06, sd 0.02). Conclusion: Traumatic injury events, including assault-related events, are spatially associated with the number of retail alcohol outlets and socioeconomic deprivation. Efforts to improve patient outcomes must extend beyond the walls of the hospital because the factors associated with injury persist in the environment before and after the traumas occur. The risk factors for traumatic injury in Arizona communities are multifactorial and represent both environmental hazards and individual choices. Therefore, interventions aimed at reducing the costs of trauma must be geographically targeted and risk-specific.