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The national and provincial burden of transport injuries in Iran between 1990 and 2021

Abstract

Transport injuries (TIs) are a major cause of mortality and morbidity worldwide, and Iran, with its rapid demographic transitions in recent decades, is no exception. This study aimed to assess the burden of TIs in Iran and its provinces from 1990 to 2021. Estimates from the Global Burden of Diseases (GBD) 2021 were used to report age-standardized rates (ASRs) for the prevalence, incidence, mortality, and disability-adjusted life years (DALYs) of TIs by sex, age group, injury type, province, and Socio-demographic Index (SDI). In 2021, Iran recorded 1.147 million (95% uncertainty interval (UI): 1.014 to 1.287 million) incident cases of TIs with an age-standardized incident rate of 1341.9 per 100,000 (95% UI: 1193.7 to 1495.1). Compared with 1990, its prevalence, incidence, death, and DALY rates decreased by − 52% (95% UI: − 54% to − 50%), − 52% (95% UI: − 55% to − 50%), − 62% (95% UI: − 65% to − 58%), and − 64% (95% UI: − 67% to − 61%), respectively. At the provincial level, Tehran (233.1; 95% UI: 191.3 to 304) had the lowest age-standardized DALY rate, while the highest DALY rate was for Sistan-Baluchistan (2155.3; 95% UI: 1866.2 to 2478.3). In addition, age-standardized DALY rates were mainly higher for males, the 20–24 age group, and provinces with a lower SDI. Despite a significant decrease in TIs in Iran since 1990, they still pose a significant burden, with notable disparities across provinces and demographic groups. Targeted prevention programs focusing on high-risk populations, such as young adults and lower-SDI provinces with lower SDI, are recommended.

Introduction

Transport injuries (TIs) are among the major causes of mortality and morbidity worldwide, accounting for approximately 50 million injuries and 1.35 million fatalities annually1. In Iran, TIs are reported as the third most common cause of death, with 21,122 deaths per year2. Furthermore, transport injuries place a significant strain on the healthcare system and economy, consuming substantial resources3.

The burden of TIs varies significantly across regions, countries, and even provinces. This was confirmed by Sadeghian et al., who found a significant disparity in the burden of TIs across provinces in Iran. Notably, Fars and Sistan-Baluchestan, two southern and eastern provinces, had the smallest decrease in the burden of TIs, despite an overall decline since 1990 in Iran2. Factors such as road infrastructure, traffic law enforcement, and demographic conditions can contribute to these differences. While data on these factors at the provincial level is limited, province-specific TIs estimates would provide a clearer understanding of their impact, helping plan targeted policy interventions.

Furthermore, the impact of TIs differs among various age and gender groups. For instance, males, particularly young adults, tend to engage in risk-taking behaviors such as speeding, reckless driving, and lower compliance with traffic laws. They are also more likely to be involved in crashes due to their inexperience and different risk perceptions compared to older age groups4. Given the identified disparities, adopting age and gender targeted approaches would be beneficial in the context of transport injuries. The Graduated Driver Licensing (GDL) program is one such targeted intervention. GDL implements a three-phase system to obtain a full driving license and focuses on supervised learning phases, especially for adolescents. A systematic review by Peden et al., reported effectiveness of GDL in reducing motor-vehicle-related injuries and fatalities for adolescent5. Additionally, one study found a 59% reduction (p < 0.001) in the rate of fatal motor vehicle crashes in 14- to 18-year-olds after implementing GDL, whereas the reduction was not significant for adults aged 19 years and older6. Considering the importance of targeted approaches, identifying vulnarbale age and gender groups, such as young adults, can aid in more evidence-based decision-making.

Despite a significant decrease in its burden in recent decades, TIs remain a major health concern in Iran. As reported in a previous study, in 1990, TIs ranked as the sixth cause of disability-adjusted life years (DALYs) among all causes in males. However, in 2015, it ascended to second place, following cardiovascular diseases7. To address this issue, it is necessary to implement comprehensive, evidence-based intervention programs.

The present study aimed to update prior research by using the latest Global Burden of Disease (GBD) data. It focuses on identifying patterns characteristic of different age and gender groups in terms of the burdon of TIs. Additionally, it reports estimates for provinces with a high burden in Iran, particularly those with persistently high burdens and minimal improvement over time.

The Institute of Health Metrics and Evaluation (IHME) provides information on prevalence, incidence, DALY, and mortality rates through Global Burden of Disease (GBD) research8. In this study, GBD 2021 data will be applied to assess the burden of TIs in Iran according to different age and gender groups, injury type and sociodemographic index (SDI). It will also provide estimates for global and Middle East and North Africa (MENA), as well as province-specific data for Iran.

Methods

Data sources

GBD studies are presented by the Institute of Health Metrics and Evaluation (IHME) and are used to determine epidemiological trends in injuries, non-communicable illnesses, and communicable diseases worldwide9. The most recent available GBD study (GBD 2021) provides data on 369 diseases and injuries and 87 risk factors according to age and sex groups in 204 countries. It also provides estimates at national and provincial levels for 21 countries, including Iran10. The GBD hierarchy classifies TIs as level 2 conditions, which fall under the category of injuries as level 1. These conditions include road injuries (divided into motorized vehicles with three or more wheels (motor vehicle) road injuries, cyclist road injuries, motorcyclist road injuries, pedestrian road injuries, and other road injuries) and other transport injuries2.

The prevalence, incidence, mortality, and DALYs per 100,000 population were evaluated in this study using GBD 2021. The Global Health Data Exchange (GHDx) and the GBD results tools provided online access to the data. The data modeling and estimation framework of GBD 2021 has been explained in prior studies. It is the same as previous GBD projects, along with corrections for miscoding and misclassification11. According to the IHME, sources such as Iran’s Demographic and Health Survey, the national forensic medicine system, hospital data samples, and the national death registration system were used to provide data for GBD 2021 and TIs in Iran10.

Statistical analysis

Estimates were obtained from the GBD 2021 study, which calculated rates by dividing the population into age groups and applying age-standardization adjustment. The GBD 2021 study provides age-standardized rates (ASRs) using the GBD world standard population. Employing ASRs enables reliable comparison across locations with different demographic structures. In contrast to raw rates, ASRs adjust for age distribution, ensuring that differences in injury burden are not solely due to variations in population age structure (12).

To ensure consistency across age and sex groups while accounting for missing data and varying injury severities, the DisMod-MR 2.1 tool, a Bayesian meta-regression model, was used, along with the Cause of Death Ensemble Model (CODEm) to provide the results of mortality calculations8.

Years Lived with Disability (YLDs) represent years of life lived in poor health or with a disability due to a specific injury or condition. They are calculated by combining the number of incident cases, disability weight (reflecting the severity of health loss), and average duration of the condition. GBD studies employ the GBD Disability Weight Survey to provide the values for these calculation. Years of Life Lost (YLLs) are computed by multiplying the number of deaths by the years of life lost due to injury, based on standard life expectancy table at the age of death. To compute the DALYs as an overall indicator of Burden of TIs in terms of fatal and nonfatal injuries, the number of YLDs and YLLs were added together12,13. In the present study, after obtaining YLD, YLL, and DALY values from the GBD 2021 database, these estimates were extracted at the national and provincial levels to compare variations in the burden of TIs across Iran.

To analyze the relationship of the SDI and the DALYs caused by TIs, Smoothing splines models were employed. This method can be used to identify possible non-linear correlations between SDI and DALY rates10. SDI values range from 0 to 1 and indicate a composite of factors, including income per capita, education level, and underage fertility. The values provided by the GBD study for each province were utilized to perform the analysis10. Expected DALY rates based on the SDI are presented, along with the observed rates for 31 provinces of Iran.

The results are reported for Iran (national and provincial), the global, and MENA regions. Estimates for the MENA region were included to provide a broader view of Iran’s regional status concerning the burden of TIs, potentially aiding in identifying regional trends, shared risk factors, and possible intervention strategies that could be adapted to Iran. The MENA region, as defined by the GBD, includes 21 countries: Tunisia, Iraq, Algeria, Qatar, Libya, Jordan, Yemen, Saudi Arabia, Afghanistan, Oman, Bahrain, Egypt, Morocco, Lebanon, Iran, the Syrian Arab Republic, Sudan, the United Arab Emirates, Turkey, and Palestine14.

An uncertainty interval (UI) of 95% was used for all estimates in this study. Uncertainty was calculated by 1000 draws sampled at each computational step obtained through several sources, such as input data, residual non-sampling error estimates, and measurement error corrections. The UIs are presented as the 25th and 975th values of the ordered draws. The R statistical program (version 3.6.1, R Foundation for Statistical Computing, Vienna, Austria) was used for all statistical analyses.

Results

National level

In 2021, there were 3.083 million (95% UI: 2.847 to 3.34 million) prevalent cases of TIs in Iran with an age-standardized prevalence rate of 3419.9 per 100,000 (95% UI: 3172.3 to 3687.6). Compared with 1990, the age-standardized prevalence rate of TIs in Iran decreased by − 52% (95% UI: − 54% to − 50%) (Table 1 and Supplementary Table 1, Additional File 1). There were also 1.147 million (95% UI: 1.014 to 1.287 million) incident cases and an age-standardized incidence rate of 1341.9 per 100,000 (95% UI: 1193.7 to 1495.1), which has dropped by − 52% (95% UI: − 55% to − 50%) since 1990 (Table 1 and Supplementary Table 2, Additional File 1). Deaths and death rates were 19,472.6 (95% UI: 18,326.1 to 20,868.6) and 22.64 per 100,000 (95% UI: 21.29 to 24.3), respectively, with a percentage change of − 62% (95% UI: − 65% to − 58%), compared with the 1990 death rate (Table 1 and Supplementary Table 3, Additional File 1). Furthermore, DALY and DALY rates were 1.123 million (95% UI: 1.043 to 1.202 million) and 1283.4 per 100,000 (95% UI: 1193.7 to 1371.3) with a percentage change of − 64% (95% UI: − 67% to − 61%), lower than 1990’s DALY rate (Table 1 and Supplementary Table 4, Additional File 1). In comparison to the global and MENA regions, Iran had higher prevalence, incidence, and DALY rates of TI cases in 2021. However, between 1990 and 2021, Iran showed a more noticeable decline in the mentioned estimates (Figs. 1 and 2).

Fig. 1

figure 1

Age-standardized point prevalence (A), incidence (B), death (C), and DALYs (D) rate for transport injuries (per 100,000 population) globally, in the MENA region, in Iran, and in Iran’s provinces in 2021 by region and sex. DALY disability-adjusted life-years, MENA Middle East and North Africa.

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Fig. 2

figure 2

Percentage change in the prevalence rate (A), incident rate (B), death rate (C), and DALY rate (D) for transport injuries (per 100,000 population) globally, in the MENA region, in Iran, and in Iran’s provinces from 1990 to 2021, by region and sex. DALY disability-adjusted life-years, MENA Middle East and North Africa.

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Table 1 Prevalence, incident cases, deaths, and DALYs of transport injuries for both sexes in 2021, and the percentage change in age-standardized rates (per 100,000 population) from 1990 to 2021 based on the GBD database.

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Subnational level

In 2021, Tehran (290,505.65; 95% UI: 270,764 to 313,282), Fars (269,254; 95% UI: 247,178 to 292,906), and Khorasan-e-Razavi (246,127; 95% UI: 227,397 to 266,061) had the highest prevalence of TI cases. In contrast, the lowest prevalence of TI cases was reported in Ilam (24,439; 95% UI: 22,568 to 26,540), Semnan (29,151; 95% UI: 27,081 to 31,611), and South Khorasan (31,062; 95% UI: 28,702 to 33,424). Also, in 2021, the highest age-standardized prevalence rates of TI cases per 100,000 population were found in Fars (4843.9; 95% UI: 4473.6 to 5237.3), Kohgiluyeh and Boyer-Ahmad (4394.8; 95% UI: 4028.3 to 4806.9), and Mazandaran (4278.1; 95% UI: 3956.4 to 4642.9), while the lowest prevalence rates were for Tehran (1774.8; 95% UI: 1660.8 to 1907.3), Qom (2379.2; 95% UI: 2214.7 to 2553.1), and Ardebil (3008.3; 95% UI: 2814 to 3238.7) (Fig. 1A; Table 1). The sex-specific prevalence rates of TI cases in 2021 are shown in Fig. 1A. In every province, men had a higher age-standardized prevalence rate of TI cases than women.

Compared with 1990, Qom (− 64%; 95% UI: − 65 to − 63%), Zanjan (− 59%; 95% UI: − 61 to − 57%), and Ardebil (− 59%; 95% UI: − 60 to − 57%) had the greatest reductions and percentage changes of age-standardized prevalence rates in TI cases per 100,000 by the year 2021. Mazandaran (− 43%; 95% UI: − 45 to − 41%), Sistan-Baluchistan (− 43%; 95% UI: − 46 to − 40%), and Fars (− 44%; 95% UI: − 45 to − 42%) had the smallest reduction of prevalence rates (Fig. 2A; Table 1). As represented in Fig. 2A, reductions in age-standardized prevalence rates of TI cases were greater among females than males across all provinces.

Moreover, Fars (1907.7; 95% UI: 1694.6 to 2136.9), Kohgiluyeh and Boyer-Ahmad (1719.6; 95% UI: 1510.7 to 1945.1), and Mazandaran (1693.4; 95% UI: 1494.7 to 1903.6) were reported to have the highest age-standardized incidence rates of TI cases per 100,000 in 2021. However, the lowest incidence rates of TI cases were for Tehran (663.8; 95% UI: 592.9 to 746.5), Qom (905.6; 95% UI: 807.8 to 1019.6), and Ardebil (1180.5; 95% UI: 1046.9 to 1323.1) (Fig. 1B; Table 1). The sex-specific incidence rates of TI cases in 2021 are depicted in Fig. 1B. As shown, in every province, men had a higher age-standardized incidence rate of TI than women, similar to the prevalence rates.

Between 1990 and 2021, Qom (− 64%; 95% UI: − 66 to − 62%), Zanjan (− 61%; 95% UI: − 63 to − 58%), and Ardebil (− 58%; 95% UI: − 61 to − 55%) were reported to have the greatest reduction in age-standardized incidence rates in TI cases per 100,000 population. In contrast, Sistan-Baluchistan (− 43%; 95% UI: − 47% to − 39%), Mazandaran (− 43%; 95% UI: − 46% to − 39%), and Fars (− 44%; 95% UI: − 48 to − 40%) had the smallest reduction in incidence rates (Fig. 2B; Table 1). As presented in Fig. 2B, reductions in age-standardized incident rates in TI cases were greater among females than among males across all provinces.

Sistan-Baluchistan (38.2; 95% UI: 32.7 to 45), Fars (38; 95% UI: 32.1 to 44.6), and Kerman (33.5; 95% UI: 28.7 to 38.8) had the highest age-standardized death rates of TI cases per 100,000 in 2021. In contrast, the lowest death rates were observed in Tehran 3.1 (2.5, 4.7), Qom 12.4 (10.4, 15.6), and Alborz (15.1; 95% UI: 12.6 to 18.3) (Fig. 1C; Table 1). The sex-specific incident rates of TI cases in 2021 are depicted in Fig. 1C. Although the disparity in death rates between males and females in Tehran was minimal, the death rate of TI cases was higher among males than females across all provinces.

Compared with 1990, Qom (− 71%; 95% UI: − 77 to − 62%), Markazi (− 68%; 95% UI: − 75 to − 61%), and Kurdistan (− 68%; 95% UI: − 75 to − 60%) had the greatest reductions and percentage changes of death rates in TI cases per 100,000 in 2021. Mazandaran (− 49%; 95% UI: − 60 to − 35%), Khuzestan (− 51%; 95% UI: − 60 to − 39%), and Fars (− 53%; 95% UI: − 64 to − 41%) were found to have the smallest reduction in death rates (Fig. 2C; Table 1).

Also, Sistan-Baluchistan (2155.3; 95% UI: 1866.2 to 2478.3), Fars (2115.9; 95% UI: 1826 to 2420.6), and Hormozgan (1861.5; 95% UI: 1586.4 to 2135.2) had the highest age-standardized DALY rates of TI cases per 100,000 in 2021. In contrast, the lowest DALY rates of TI cases were reported in Tehran (233.1; 95% UI: 191.3 to 304), Qom (691.4; 95% UI: 585.9 to 853.1), and Alborz (860.8; 95% UI: 733.9 to 1005.8) (Fig. 1D; Table 1). The sex-specific incidence rates of TI cases in 2021 are depicted in Fig. 1D. Males had a higher age-standardized DALY due to TIs than females across all provinces except for Tehran, where the disparity was smaller.

Since 1990, Qom (− 73%; 95% UI: − 78 to − 66%), Zanjan (− 72%; 95% UI: − 77 to − 65%), and Kurdistan (− 71%; 95% UI: − 76 to − 66%) have been found to have the greatest reduction in DALY rates in TI cases per 100,000 by 2021. However, Mazandaran (− 52%; 95% UI: − 60 to − 42%), Khuzestan (− 53%; 95% UI: − 60 to − 44%), and Fars (− 54%; 95% UI: − 63 to − 45%) had the smallest reduction in DALY rates (Fig. 2D; Table 1).

Age and sex patterns

For both sexes, the overall prevalence of TI peaked in 2021 in the 35–39 age group and then declined with age. Moreover, the prevalence rate reached its highest point in the 90–94 age group for both sexes (Fig. 3A).

Fig. 3

figure 3

Prevalent cases count and prevalence (A), Incident cases count and incidence rate (B), Death cases count and death rate (C), and the number of DALYs and DALY rate (D) for transport injuries (per 100,000 population) in Iran, by age and sex in 2021; shading indicates upper and lower uncertainty intervals of 95%, respectively. DALY disability-adjusted life-years, MENA Middle East and North Africa.

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Incident cases of TI reached a high point in ages 20–39 for males and in age groups of 0–4 and 30–34 for females. Furthermore, for males, the incidence rate of TI cases peaked in the 20–24 age group and then declined as age increased. However, this pattern was not evident in females (Fig. 3B).

The death rate of TI cases reached a high point in the 20–24 age group for males, followed by a decline, after which it resumed an upward trend as age advanced. In females, the death rate steadily increased with age. Furthermore, the number of TI deaths was highest in the 30–34 and 35–39 age groups for both sexes (Fig. 3C).

The DALY number of TI cases was highest in the 30–34 and 35–35 age groups for both sexes. In addition, the DALY rate peaked at the 20–24 age group in males. But, in females, the DALY rate maintained an upward trend as their age increased (Fig. 3D).

Burden by injury category

Motor vehicle road injuries had the highest age-standardized rates of prevalence (1441.9; 95% UI: 1259.5 to 1666.9), incidence (670; 95% UI: 585.3 to 772.8), death (11.83; 95% UI: 9.88 to 15.25), and DALY (661.8; 95% UI: 572.4 to 823.2) in Iran in 2021, followed by pedestrian and motorcyclist road injuries with DALY rates of 338.4 (95% UI: 218.1 to 452.8) and 193.5 (95% UI: 153.2 to 235.9), respectively. Cyclist road injuries had higher prevalence and incidence rates compared to other road and transport injuries; however, their death and DALY rates did not show this pattern (Fig. 4A–D and Supplementary Table 5).

Fig. 4

figure 4

Age-standardized point prevalence (A), incidence (B), death (C), and DALYs (D) rate for transport injuries (per 100,000 population) in Iran, in 2021 by injury category. DALY disability-adjusted life-years.

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Burden by socio-demographic index (SDI)

In 2021, the age-standardized DALY rate decreased as the SDI increased, indicating a negative relationship between the SDI and age-standardized DALY rate for TIs. Fars, Kerman, Markazi, and Hamadan had higher than anticipated age-standardized DALYs. In contrast, age-standardized DALYs in Ardebil, Tehran, and Qom were lower than anticipated (Fig. 5).

Fig. 5

figure 5

Age-standardized DALY rates of transport injuries for 31 provinces of Iran in 2021 by SDI; expected values based on the sociodemographic index and injury rates across all provinces are marked by the black line. The observed age-standardized DALY rates are shown as 32 plotted points for each province from 1990 to 2021. Provinces with a higher-than-expected DALY rate are above the black line, and provinces with a lower-than-expected DALY rate are below. DALY: disability-adjusted life-years; SDI: socio-demographic index.

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Discussion

The current study used the GBD 2021 data to determine the burden of TIs in Iran from 1990 to 2021. In 2021, there were 3.083 million prevalent cases, 1.147 million incident cases, and 19.472 thousand deaths in Iran. Iran had higher prevalence, incidence, DALY, and Death rates compared the global and MENA regions, however it showed a more noticeable reduction in these rates over the study period. The burdon of TIs varied across provinces and among different age and sex groups. Among the provinces, highest DALY rates were reported for Fars and Sistan-Baluchistan, with neither having much improvement since 1990. Males, particularly those aged 20–24, had the highest incidence and DALY rates, while older adults (70 + years) had the highest prevalence and death rates. A negative association was observed between the Socio-demographic Index (SDI) and DALYs, highlighting the influence of socioeconomic factors on injury burden.

The burden of TIs is assessed using prevalence, incidence, mortality, and DALYs. While the prevalence of TIs indicates the number of individuals living with injury-related disabilities, the incidence rate highlights the ongoing occurrence of new injury cases, emphasizing the persistent risk of transport injuries despite existing preventive measures. The mortality rate shows the burden of TIs resulting in death, whereas DALYs, which combine both YLLs due to premature death and YLDs, reflect the impact of TIs in terms of both fatal and non-fatal outcomes10. Consequently, factors such as road safety laws, vehicle safety standards, transportation infrastructure, injury severity, and post-injury healthcare influence both the occurrence and outcomes of TIs and their overall burden15.

Compared with the global and MENA regions, Iran had higher prevalence, incidence, and DALY rates of TIs in both 1990 and 2021. This finding is consistent with a previous study that reported higher rates in Iran using GBD 2019 data2. Iran has experienced 2.5 times population growth along with rapid urbanization in recent decades16,17. Rapid urbanization and an inadequate transport system increase the risk of transport injuries. For instance, overcrowded and poorly maintained roads contribute to a higher risk of traffic accidents18. In addition, weak enforcement of traffic laws, such as speed limits, seatbelt usage, and driving under the influence, can lead to increased traffic accidents. Lower safety standards for cars, lack of proper public awareness, and common reckless behavior among drivers may also increase the risk of TIs19,20. A systematic review of 20 studies in Iran reported roadway defects and improper road surfaces as mortality risk factors for traffic injuries19. Despite having higher rates of TIs, Iran experienced a more noticeable reduction in these rates between 1990 and 2021. This could be due to the availability of safer transportation options, such as switching to automobiles with higher safety standards and using public transportation21,22. The recent increase in public awareness and official efforts in Iran may have contributed to these results. A study reported a 3.3% decrease in deaths due to road traffic injuries after enforcement of mandatory use of seatbelts23,24.

As reported in this study, there was a negative association between the SDI and DALYs of TIs. In most regions, a higher SDI indicates greater access to vehicles with higher safety standards. Furthermore, regions and provinces with a higher SDI tend to have properly developed transport infrastructure, better road maintenance, and better road services15,25. However, various social and economic factors may play a role in the SDI and TI. For instance, in some low-income countries, living in urban regions with a higher SDI would mean more access to motor vehicles and more TIs compared with rural areas, where access to motor vehicles is limited26. By contrast, in higher-income countries, residents of higher SDI regions may prefer to travel with air and rail transport vehicles, with a lower likelihood of injury15. This emphasizes the importance of considering the local context when interpreting data on the relationship between the SDI and TIs.

Among the different types of transport injuries, road traffic injuries compose a substantial proportion of it in Iran. As reported, motor vehicle, pedestrian, and motorcyclist road injuries are the three leading causes of the burden of TIs in Iran. Considering the high rate of traffic injuries among pedestrians and motorcycle riders it would be helpful to put on initiatives such as encouraging the use of helmets and installing safety measures like speed bumps and necessary road signs. In the cyclist road injuries subcategory, we observed lower death and DALY rates; however, the prevalence and incidence rates were not as low. This could be explained by the fact that cyclists typically travel at lower speeds and avoid highways and roads designed for higher-speed vehicles, which may reduce the severity of injuries in this subcategory. As a subcategory of TIs, other transport injuries, such as air and rail travel, contribute to a lesser extent to Iran’s overall burden of TIs. Air and rail travel are known for their lower injury risk, yet in the event of an incident, they can result in severe injuries and multiple casualties, which should not be overlooked in programs aimed at reducing burden of TIs15.

According to the present study, the burden of TIs did not have a consistent pattern across the provinces in Iran. Among the provinces, Tehran, Fars, and Khorasan-e-Razavi had the highest prevalence of TIs. However, the highest incidence rates were reported for Fars, Kohgiluyeh and Boyer-Ahmad, and Mazandaran. Despite its dense transportation landscape, Tehran, as Iran’s capital, had the lowest overall burden of TIs, likely because of better infrastructure and stricter enforcement of traffic laws. In contrast, Sistan-Baluchistan and Fars had the highest mortality and DALY rates, indicating a significant fatal and nonfatal impact of TIs in these regions. Furthermore, these provinces were among those with the least improvement in DALY rates and burden of TIs over time. This highlights how the issue of TIs has remained persistent, underlining the need to address factors such as road safety, traffic law enforcement, proper healthcare, and post-injury care access in those areas.

A previous study also reported a significant disparity in the burden of TIs across the provinces in Iran. The Tehran and Sistan-Baluchistan provinces were reported to have the lowest and highest burdens of road traffic injuries in 2019, respectively2. Other studies reported similar heterogeneity across provinces. Shavaleh et al. reported a higher incident rate of road traffic crashes in the central and eastern provinces of Iran27. However, in contrast to our findings, Najimi-Varzaneh et al. reported the lowest pooled road traffic accident rate for Fars province in their systematic review, which included studies published between 1995 and 2018. This may be explained by the different methods applied compared with GBD studies, which use a consistent, global analytical approach, likely integrating recent hospital and official records8,28.

Mentioned heterogeneity also exists in other countries29. A previous study that analyzed the provincial distribution of traffic accidents in Turkey reported a higher death rate for roads connecting major cities (Erdogan)30. Variations in transportation infrastructure, road conditions, compliance with traffic laws, social behaviors, and healthcare access could contribute to the reported disparities31. These differences highlight the importance of considering province-specific factors during the policymaking process.

According to our findings, the burden of TIs was not the same for the different age groups in Iran, with distinct trends of rate and number in prevalence, incidence, mortality, and DALYs. Males in the 20–24 age group had the highest incidence and DALY rates, along with a peak in the death rate. Other studies have reported similar findings in this age group. Chen et al. reported the highest incidence rates of transport injuries for men in the 20–24 age group globally32. The high incidence rate in this age group can partly be due to behavioral factors; for instance, young adults tend to manifest risk-taking behaviors more frequently4. Additionally, the high DALY and mortality rates in early adulthood indicate the severity and long-term consequences of their injuries. However, this pattern was less prominent among females in the same age group in Iran, underlining a distinction in contributing factors according to sex.

For the 30–39 age range, both males and females had higher prevalence, incidence, mortality, and DALYs. The 30–39 age range tends to have a higher exposure to road traffic because of their workforce participation, daily mobility, or involvement in responsibilities such as commuting and transporting family members. Despite the similarities, the disparity across age groups for number of prevalence, incidence, mortality, and DALYs was more noticeable for males. This can be explained by men being more likely to work in jobs that involve frequent transportation, particularly those that require intercity travel, which has a high risk of resulting in severe injuries33,34.

Individuals aged 70 and older had the highest prevalence and death rates in our study. Due to their limited recovery capability and the likelihood of underlying conditions, such as low bone density, they may experience a cumulative effect of persisting prior injury-related disabilities, leading to a higher prevalence and death rate from TIs. However, in males, older individuals had a lower DALY rate compared to young adults. This can be explained by the contribution of YLDs and YLLs in calculating DALYs. Therefore, in cases of disability or premature death due to TIs, older individuals lose fewer potential years of life based on their expected lifespan compared to younger ones, which results in smaller DALYs for the older population15,35.

Limitations

This study had some limitations. First, the present study applied GBD data for analysis, which relies on modeling methods rather than primary data, to provide estimates in case of a lack and/or dispersion of data. Second, considering the social and economic factors unique to every region, it may be challenging to interpret data, especially according to the SDI and gender groups. Third, although the COVID-19 pandemic has been reported to affect TIs both in terms of incidence and medical service provision, it was not evaluated in this study36.

Conclusion

The burden of TIs in Iran has decreased significantly since 1990; however, it remains higher than that in the Global and MENA regions. TIs show an uneven distribution across provinces as well as age and gender groups in Iran. Provinces of Fars and Sistan-Baluchistan had a high burden of TIs persistently, however, Tehran had the lowest rates of burden despite its population. Young adults (20–24 years) had the highest incidence rate of TIs, while older adults (70 + years) had the highest prevalence and mortality rates.

Given these findings, applying targeted interventions would mitigate the impact of TIs. While older people would most benefit from better post-injury care and road safety measures, driver education programs like GDL could help young adults avoid TIs. Therefore, more research is required to examine demographic and regional risk factors as well as to assess the efficacy of these interventions.

Data availability

“Data sets generated during the current study are available from the corresponding author on reasonable request (Hassan Soleimanpour) upon reasonable request.”

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Acknowledgements

The authors would like to appreciate the Clinical Research Development Unit, Imam Reza General Hospital, Tabriz, Iran, for their cooperation in conducting this research. This article was written based on the dataset from a thesis by Amin Abbasi entitled “The National and Provincial Burden of Transport Injuries in Iran between 1990 and 2021”. This study was registered in Tabriz University of Medical Sciences (Code No: 75348).

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Authors and Affiliations

Emergency and trauma care research center, Imam Reza General Hospital, Tabriz University of Medical Sciences, Tabriz, Iran

Amin Abbasi, Moloud Balafar, Mahboub Pouraghaei, Sajjad Ahmadi & Hassan Soleimanpour

Department of Anesthesiology and Critical Care Medicine, Faculty of Medicine, Tabriz University of Medical Sciences, Tabriz, Iran

Samad E.J. Golzari

Department of Anaesthesiology and Intensive Care Medicine, Klinikum Dortmund, University Witten/Herdecke, Herdecke, Germany

Samad E.J. Golzari

Clinical Research Development Unit of Tabriz Valiasr Hospital, Tabriz University of Medical Sciences, Tabriz, Iran

Maryam Soleimanpour

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Amin Abbasi

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