Introduction
Trauma is one of the main causes of death in the Netherlands, especially in the younger population, and the number of trauma victims is increasing significantly. In 2015, more than 80,000 patients have been admitted to a Dutch hospital due to traumatic injury [
1]. The majority of these injuries were related to fall accidents, road traffic accidents and suicide [
2,
3]. Previous research suggested that there was an association between the social characteristics of the patients and their outcome after traumatic injury. For example, patients with a lower intelligence level, specific racial-ethnic background and no insurance policy had a higher risk on hospitalization and mortality due to trauma [
4‐
10].
However, there is a scarcity of studies which examined the association between socioeconomic status (SES) and outcome after traumatic injury. Moreover, most research is focused on work-related injuries and does not take other important characteristics, like comorbidity of the patient, into account. In addition, nearly all reviews used only the education level to determine SES, whereas other indicators, such as household income and employment status, should be taken into consideration as well [
11,
12].
The aim of this study is to examine whether there is an association between the SES and the clinical outcome of polytrauma patients after injury. Examining the association between SES and traumatic injuries can be useful for public health organizations in guiding their allocation of resources and to prioritize the implementation of preventative measures in specific neighborhoods.
Discussion
This analysis of polytrauma patients was performed to investigate a possible association between patients’ SES and clinical outcome after traumatic injury. We hypothesized that trauma patients with low SES levels were associated with worse clinical outcomes.
The analyses revealed that the lowest SES group seemed to include younger patients, with a doubled number of penetrating injuries compared to the highest SES group. However, in contrast with previous research in other countries, we could not find a significant association between socioeconomic status and mortality. Possible explanations include the following.
First of all, the geographical location of our trauma region was advantageous for this study, since it is considered as one of the most culturally diverse cities in the Netherlands. However, it is important to point out the current SES of the Dutch society. Indeed, there is a gap between the lowest and highest SES, but—compared to many other countries— this is quite small. Additionally, the social safety net of the Dutch government is actively supporting cases of socioeconomic deterioration, to promote equality within the society. Therefore, it is quite evident that we could not find any significant associations with our relatively homogeneous study population.
However, we did find a significant association between SES and length of stay at the ICU. Even though the association was minimal (unstandardized coefficient − 0.02), it is important to identify possible causes for these findings. As can be seen in Table
1, no significant differences were found in gender, ISS or comorbidity to explain these results. The combined predictor model, correcting for SES, age, gender, comorbidity, type of injury, mechanism of injury, ISS and AIS, still showed significant differences. Psychological factors in the lower SES groups, with more often mental stress and pressure to achieve due to work-related subjects, might have decreased their state of health in advance, resulting in a longer stay at the ICU [
22]. However, additional analyses are recommended, for example regarding hypotension rate or amount of blood loss to eliminate or confirm these as possible confounders for our results.
Unexpected results were found in the subanalysis regarding the expected survival and the actual (observed) survival. The actual survival does not correspond with the predicted survival (based on TRISS) in the lowest SES group, with a difference of approximately 3–4% (Table
4, Fig.
1). This might suggest that other factors are required in analyses including lower SES groups. Furthermore, it is important to notice the more deviant PSNL15 scores, which do not match the TRISS nor the actual survival. Further adjustments for more accurate calculations can, therefore, be advisable.
Apart from that, there are limitations in our study that might (partially) explain the discrepancy in findings as well. One of them includes the difference in SES data that were used to examine the association. To improve the accuracy of the results, we used the database of StatLine Netherlands, which used four indicators to determine SES. However, the use of postal codes might have created risk of bias since the assumption of population homogeneity within a postal code is made, especially in emerging areas. Another limitation was the limited size of the included area. We were only able to obtain data from two level 1 trauma centers (Amsterdam UMC, location VUmc, and Northwest Clinics Alkmaar), whereas the inclusion of more hospitals in the Netherlands might have given a more accurate insight. Furthermore, our database did not include patients who died on scene due to their injuries. Exploring the proportion of patients who died on scene per socioeconomic status might provide additional insight in the association between SES and mortality. Finally, appropriate attention should be paid to the external validity of our results and how these can be extrapolated, given the uniqueness of our mixed study population.
Conclusion
No direct association was found between SES and mortality. However, patients from lower SES suffered from severe injuries at a younger age, showed more penetrating injuries and a longer stay at the ICU. Additionally, discrepancies were found between the expected and actual survival. Therefore, additional research is recommended to find explanations for these findings and to create a more enhanced overview.