To our knowledge, this is the first national study and among few studies in the literature to analyze the association between socio-demographic factors, injury characteristics, health outcome and hospital charges and LOS among patients with RTI. The findings showed that hospital charges and LOS associated with RTIs varied by age, gender, socio-economic status, injury characteristics, health outcome of patients, and type of road users.
Although the average hospital charges in this study were lower compared to reports from HICs [6–9, 32], the increasing number of RTIs and deaths in Iran, impose a huge economic burden on the Iranian society. During the years 2000 to 2004, nearly one million people were injured and more than 100,000 died due to traffic crashes in Iran .
Local studies conducted in hospitals in Tehran city have reported LOS ranging from 5 to 7.8 for trauma patients in general [14, 33–35], which is in line with the average LOS for RTI reported in this study. It is difficult to compare LOS between countries, due to variations in the organization of trauma care and differences in injury patterns and a comparison of our results with previous studies show conflicting results. The average LOS for RTI victims in the current study was similar to the results of one study done by Odero et al., measuring health care utilization among all types of injuries in one hospital in Indiana, USA . On the other hand, the mean LOS in the current study was higher than in some other studies done in HICs [6–8, 32] and also in other LMICs . In contrast, the average LOS for RTIs in the current study was lower than the average LOS for RTIs reported in Trinidad and Tobago , Kenya , Spain , New Zealand  and Greece . The mean total hospital charges, on the other hand, were much lower in the current study compared to studies conducted in HICs [6–9, 32]. Some part of the lower hospital charges, compared with HICs, can be explained by the subsidized health care system and also the general low service costs in Iran.
The findings showed that hospital charges and LOS varied with age, gender, socio-economic status, injury characteristics and health outcome of the patients. Consistent with previous knowledge [11, 33, 34, 42], RTI victims in the current study were predominantly male (male–female ratio 3.4), mainly in productive age and from lower socioeconomic groups (both in terms of education and occupation). Men had longer LOS than women. The findings also showed that LOS decreased with increasing level of education. This result should be treated with caution since only 4% of the patients had university and higher level education. Shorter LOS in this group of patient might be explained partly by faster recovery due to self-care and better therapeutic compliance.
In line with other studies [6, 7, 10], patients with more severe injuries (higher ISS or lower GCS) had longer LOS and higher total hospital charges. LOS was, not surprisingly, a significant predictor of higher total hospital charges. This corroborates with other studies on the same topic in HICs [6, 7]. The findings also showed that being a blue-collar worker was associated with longer LOS. Based on the information in this study and previous studies in Iran [14, 33–35], the severity of injury was higher among blue-collar workers (often characterized as lower socio-economic groups, and mainly vulnerable road users, such as motorcyclists or pedestrian, in the context of Iran) compared to white-collar and other occupation groups. Different pattern of injury among blue-collar workers compared with other occupation groups might contribute to longer hospitalization periods in this group.
An important finding of the current study was the low coverage of health insurances (more than half of the patients did not have any type of health insurance) and the significant effect of having insurance on hospital utilization. The findings showed that insured patients stayed longer in hospital compared to uninsured, after controlling with socio-demographic and injury-related factors. The findings support the conclusion that lack of health insurance coverage could be a barrier preventing or limiting access to care, although the limitations of the data do not allow conclusions as to whether those covered by health insurance had better health outcomes or have access to better quality care than those not covered. Another explanation for this result can be supplier-induced demand in hospital sector in the country. Similar results were found in two studies in the US, demonstrating that uninsured or self-paying children were charged less and had shorter LOS than children covered by Medicaid [6, 7]. On the other hand, a study conducted in Guadalajara, Mexico, indicated lower hospital costs for insured patients . Insurance status has also been shown to be an important factor influencing utilization of health care services in general in Iran . A new law was approved in Iran in 2008 (after the study period of the current study), which meant all hospital care for RTIs victims became free of charge. The effect of the new law has not been evaluated yet and further studies are needed to investigate the effect of the new law on hospital charges and LOS (and in general, resource burden) among RTI victims and also the effect of insurance on other types of traumas.
Studies have shown that patients who died during hospitalization incurred significantly higher hospital charges (mainly due to utilizing expensive intensive care during their hospitalization) but shorter LOS compared with patients who survived their injuries [6, 7]. The findings from the current study indicated that the patients who died in hospital had shorter LOS compared to those survived and there was no significant difference in total hospital charges between two groups, after controlling for other factors in the multivariable model.
The findings also showed that total hospital charges and LOS varied based on type of road users. Compared with other road users, being a pedestrian was associated with lower hospital charges but longer LOS. Longer LOS for pedestrians has also been reported in previous studies [40, 44]. The pattern of injury sustained by pedestrians (including head, spinal and lower extremity injuries), compared with other road users, could, to some extent, explain their longer hospital stay. Bicycle riders had higher hospital charges (but shorter LOS compared with other road users). This could be explained by higher risk of head injuries among cyclists resulting in expensive diagnostic and therapeutic procedures.
The findings indicated that use of safety equipment among the patients was very low and it did not have a significant effect on hospital charges and LOS. A new law making compulsory the use of seat-belts (for drivers and front seat passengers) and motorcycle helmets was introduced in 2001 in Iran, but based on the findings of the current study and a few other studies [13, 14, 33, 35], the use of helmets and seatbelts seem to be exceptionally low. However, figures from recently published studies have shown an increase in the rate of seat-belt use among car occupants [45, 46]. Research show that increased enforcement is one of the most effective methods to increase usage of safety equipment . Since 2005 several interventions, including law enforcement of seat-belt and helmet use, have been implemented by the Traffic Police in Iran , however the effect of these intervention on usage of safety equipment has to be studied further
The positive effect of safety helmets and seat-belts on reducing fatal injuries is well-documented . The findings of the current study that none of the patients who had used safety helmets died in hospital compared to 3% of those who had not used helmets and this difference was statistically significant. Previous studies have shown that not wearing a safety helmet or seat-belt is associated with higher hospital charges and longer LOS [16–19]. However, the results of the current study showed no significant differences in hospital charges and LOS among the patients, who did not use safety helmets and seat-belts and those who used. These findings could be explained by the small number of patients who had used safety equipment in the country.
Another important finding of this study was that the majority of patients were transported to the hospitals by means of transport other than ambulances. Low usage of EMS ambulances has also been reported in other studies in Iran [14, 34, 48]. In addition, the average pre-hospital transportation time reported in the current study was longer than the reported time in previous studies in urban areas of Iran [34, 49, 50]. Two out of three studies [49, 50] which have investigating pre-hospital transportation time in Iran have measured only EMS ambulances transportation time (with average 10 and 18 minutes, recorded by EMS personnel), and one study  reported the average time for all transportation means (2 hours, reported by the patients). The transportation time in the current study was based on self-reports and it might have led to an over-estimation of the time. Moreover, since most patients admitted to the hospital in this study and previous studies in Iran [33, 34] had moderate injury severity (low ISS and high GCS), it can be concluded that many severely-injured patients die before reaching the hospital due to more severe crashes, long pre-hospital transportation time and, insufficient pre-hospital trauma care facilities [13, 51, 52].
INTRD is the largest trauma registry database in Iran, but it has some limitations that may affect the findings of this study. First, the database is hospital-based and might not be representative of the pattern of RTI in general. Second, the database excluded the patients who stayed at the hospital less than 24 hours. These patients may have received care at the ED and have been discharged or died in the ED (or before reaching the hospital) because of the severity of their injuries. Excluding these patients from the database may affect the results of the study by underestimating LOS and hospital charges and in general the burden of RTI. Third, total hospital charges are billed charges and do not reflect actual payments nor true hospital costs due to factors such as government subsidies to hospital services and medicines, discounts and exemptions given to some patients by the hospitals and also not including all out-of-pocket payments by the patients. Moreover, the non-medical direct costs such as transportation costs and the indirect costs related to lost productivity, as well as the costs associated with the pain and suffering by victims and relatives are not included. Measuring these costs, although important, was beyond the scope of this study. Fourth, information such as pre-hospital transportation time and use of safety equipment (safety helmet/seat belt) are self-reported. Therefore these two variables could be over-estimated, the first one because of recall bias and the second one based on false claims (to avoid legal consequences). Moreover, in cases when the patient was too ill to report this information, it was supplied by the accompanying person, which may have led to misreporting.
Despite these limitations, the findings demonstrate a significant morbidity and resource burden associated with RTIs. By describing epidemiology, hospital charges and LOS based on different socio-demographic groups and based on outcome and injury-related characteristics of patients, the findings of this study can be used for developing interventions to improve quality of care and outcome of the patients and also help to design targeted prevention measures. Primary prevention is the preferred means of reducing the impact of RTIs on the health sector, families, and society. Use of evidence-based interventions such as increasing use of safety equipment through law enforcement and public education can be enhanced in the context of the study in order to decrease traffic-related mortality and morbidities.