The study outcomes indicate that there is no significant difference in the crude mortality due to RTA between Arabs and Jews. However, after accounting for possible confounding factors, mortality among Arab casualties was greater in comparison to Jewish casualties. The fact that this difference emerges after adjusting for confounders can be explained by the differential distributions and imbalance between Arabs and Jews in risk factors for mortality. The favorable characteristics among Arab casualties could exert a stronger effect in masking the mortality difference expected that would arise from the risk factors. Firstly, Arab casualties were younger than their Jewish counterparts, which was noticeable even after taking into consideration their younger age in the general population. In 2017, for example, the percentage of persons aged 0–24 years was 54.5% in the Arab population vs. 41.2% in the Jews population [16, 23]. This could mask the true mortality difference in the unadjusted mortality, as supported by our observation in the adjusted analysis. Secondly, additional hospitalization characteristics could be considered favorable to Arab casualties in masking the expected mortality difference between Arabs and Jews. For example, there were significant differences in hospital resource utilization, which is very likely to stem from the fact that Arab casualties suffered from more severe injuries compared with Jews. Arabs had greater rates of utilization of high impact interventions such as treatment in trauma resuscitation unit, surgical intervention and admission to the ICU, as well as evacuation by helicopter EMS; all of which would be expected to properly address the possible risk factors for increased mortality. This is supported by our observation that the difference in mortality between Arabs and Jews became apparent when hospitalization characteristics (hospital admission time, undergoing imaging study, undergoing surgery, admission to ICU, LOS) and means of evacuation were entered into a model accounting for age, gender, ISS, injury type and transfer status. This implies that hospitalization characteristics and means evacuation were favorable to Arabs to be discharged alive from hospitalization following RTA. Rapid prehospital transport, early hospital and surgical treatment are among the critical factors to improve trauma outcomes [3,4,5,6]. The differential rates of health care interventions between the comparison groups could reflect the appropriateness of the practice of trauma care in the country, i.e., treatment is received according to needs, independently of population groups, without any discrimination. To that end, the findings of this study confirm not only the efficacy of the Israeli trauma care system but also reinforce that the national health insurance law provides the necessary medical services to all residents in an effort to narrow the gaps of inequality between population groups [29,30,31].
Critical (ISS 25+) and multiple injuries (especially including TBI) not only characterize a large proportion of the injuries among Arab casualties, but also increase the risk of mortality. This is supported by the significant reduction in the odds ratio when ISS or TBI were included into the model thus influencing mortality outcomes. It is well established that injury severity is a strong predictor of mortality, with a strong inverse relationship between injury severity and mortality [27, 32]. Likewise, severe TBI is a major risk factor for mortality [33,34,35]. The differences in injury characteristics between Arabs and Jews can be presumed to be related to their differences in road safety behavior such as seatbelt use, helmet use, use of child restraints, compliance with traffic rules and signs, as well as road infrastructure differences [13, 19,20,21,22]. In addition, the severity of crashes and its consequences on mortality outcomes may be somewhat related to travel distances (for work and education) from the periphery and rural areas to major cities where most of the employment, universities and major business centers are found [13]. Long travel distances increase exposure to RTA due to driving behaviors, especially speeding and fatigue, which increase the risk of severe and fatal accidents. This is supported by the fact that in Israel 54% of persons killed in road accidents and approximately 34% of those seriously injured occurred on non-urban roads [21]. There is also evidence to suggest that the risk of dying in a road traffic crash still depends, in great part, on where people live and how they travel [1]. Time of arrival at the hospital may be another factor contributing to the disparity in mortality between Jews and Arabs. In this study, Arabs were more likely to be admitted “outside official work hours”, which has been associated with a greater risk of mortality [36]. Although this study did not investigate factors related to “outside official work hours”, it is suggested that optimal level of care may be hampered “outside official work hours” due to reduced staffing, fatigue, non-availability of senior staff, reduced resources and use of diagnostic procedures and interventions. Health professionals working “outside official work hours” may be less experienced and have less seniority, which can ultimately affect the outcome of care among severe and critical casualties. “Outside official work hours” not only there may be fewer supervisors but also the available supervisors may be required to overseeing the work of staff members they do not know well [35, 37].
Specific subgroups of Arab casualties were found to be at higher risk for in-hospital mortality following RTA, in comparison to Jews; including, patients suffering from critical injuries (ISS 25+) and those admitted “outside official work hours”. No significant difference was found between Arabs and Jews who were admitted on weekdays. A large proportion of Arab Israelis reside in the periphery and in rural areas - along with scattered villages, which are geographically far from the major cities where hospitals, particularly level I trauma centers are located [19, 20, 22, 38]. Occurrence of injury due to RTA in such areas may lead to prolonged prehospital times due to longer distances and travel times from the accident sites to the trauma centers, and thus contributing to increased mortality rates [5]. Among patients who were admitted “outside official work hours”, when optimal level of care may be hampered [35,36,37], the impact of distance and travel time on mortality outcome may be even stronger for patients with severe and critical injuries, TBI, or injuries involving multiple body regions, which all are more prevalent among Arabs compared with Jews. The differences in mortality between Arab and Jewish causalities (after adjusting for the confounders, including prehospital time) can be attributed, at least in part, to ethnicity per se or to unknown factors that this study was not be able to identify.
This study is based on data from trauma centers throughout the country, providing a vast geographical coverage and nationally representative data of hospitalized trauma casualties. In an effort to minimize mortality disparities between Jewish and Arab traffic casualties, future studies should collect more detailed information, such as travel distances between the scene of the event and where the definitive care is received.
Limitations
The first limitation stems from the inclusion parameters of the INTR, which is the source of data for this study. Since the registry does not include patients who died at the scene of the event or on the way to hospital, or those patients who were not hospitalized; this study lacks both minor injuries and fatalities prior to arriving at the hospital. While these two extremes might differ between Arab and Jewish casualties, this study only included severe and critical injuries (ISS 16+) and thus the lack of minor injuries in the trauma registry does not affect this study. Although fatalities outside the hospital are not included, all severe and critical casualties receiving definitive care at one of the many trauma centers in Israel should be included in the registry, providing plentiful, representative and valuable information in understanding injury characteristics and outcomes, and specifically regarding injury-related hospitalizations.
Another limitation could be that co-morbidity, which affects mortality outcome, was not taken into account. However, co-morbidity was unlikely to affect our findings because the increased mortality among Arabs versus Jews persisted even after excluding from the analysis patients aged 65 years or above, among whom outcome after injury is more likely to be influenced by preexisting conditions [39]. In addition, due to lack of data this study did not examine the effect of other confounding factors, such as complications, serum lactate level and base deficit; which are associated with mortality [40,41,42]. On the other hand, ISS, a widely used tool for assessing injury severity and for determining outcome in trauma patients, was taken into account in the model [27, 43, 44]. While the most important limitation of ISS is with regard to penetrating trauma [45, 46], in this study the majority of casualties suffered from non-penetrating trauma, thus, the mortality predicting ability of ISS was unlikely to be affected.
Further, this study did not investigate the influence of socioeconomic variables and road safety practices, which could partly explain some of the results. Exploring those factors in future studies may further strengthen the outcome of this study which took into account a large number of covariates. There is evidence suggesting that characteristics, such as unsafe road practices and lifestyles, are related to increased risk of severe injury and mortality [13, 19, 20, 22, 47, 48].
