Epidemiology and Injury Characteristic Between Bicycle and Motorcycle Under 19 Population: South Korea

Bicycles and motorcycles are the main means of transportation and leisure for those under the age of 19 in South Korea. We aimed to identify epidemiology of injuries and to determine the injury characteristics and clinical outcomes of two-wheel vehicle-related accidents in individuals under the age of 19. a retrospective cohort and data, acquired from collected from 401 emergency departments (EDs) and We included patients < who experienced while two-wheeled


Introduction
Bicycles and motorcycles are the main means of transportation and leisure for those under the age of 19 in South Korea. However, this use of two-wheeled vehicles often leads to injuries. Injury is a leading cause of death and morbidity in adolescents aged 19 or younger [1]. Tra c accidents are one of the most common causes for visits to emergency departments (ED) [2]. Among them, bicycle and motorcycle crashes show different characteristics from others, such as accidents in cars. Unlike car accidents, the body is exposed directly to the external environment in twowheeler accidents. Because bicycles and motorcycles use only two wheels for balance, they can easily turn over. In addition, they have a high probability of accidents due to the in uence of road surface and environment. As a result, fatal damage, such as the head and limb injuries, may be caused [3][4][5].
In South Korea, the adoption of cycling has steadily increased due to increased interest in leisure activities and the government's policy to encourage the use of bicycles by developing bicycle sharing systems and bicycle lanes [6]. The overall use of motorcycles is also gradually increasing due to the demand for food-delivery services. As the use of bicycles and motorcycles increases, the number of tra c accidents related to them is also increasing. From 2010 to 2019, the number of tra c accidents involving motorcycles and bicycles increased from 17,672 to 20,898 and from 11,439 to 13,693, respectively [7].
Patients who visit the ED due to motorcycle and bicycle-related tra c accidents have various severities of injuries, and may also require hospitalisation. Although some previous studies have reported motorcycle and bicycle-related injuries, most studied elderly patients or all age groups [8][9][10]. Bicycles and motorcycles are easier to use for paediatric and adolescent age groups compared to other transportation because a driver's license for cars is available only after the age of 20 years in South Korea. In addition, according to the World Health Organization, road tra c injuries, including motorcycle and bicycle accidents, are consistently one of the top three causes of death for young people [11]. Tra c accidents are the second leading cause of death in South Korea under the age of 10, and the third leading cause of death under the age of 10 [12].
Previous studies comparing bicycle and motorcycle-related accidents have shown differences in injury characteristics and outcomes [10,13,14]. To our knowledge, no study has been reported to evaluate the injury characteristics and outcomes in bicyclists and motorcyclists under the age of 19. Paediatric and adolescent injuries are an important public health concern because of their high global impact on deaths and disabilities [15].
The purpose of this research was to identify the general epidemiology of two-wheeled vehicle-related injuries and to determine the injury characteristics and clinical outcomes of motorcycle-and cycle-related accidents in individuals younger than 19 years of age.

Setting and Data Collection
This study used prospectively collected data from the National Emergency Department Information System (NEDIS) between January 2016 and December 2018. The NEDIS was started in 2003, and the number of participating emergency medical institutions has increased since. There are 36 regional emergency medical centres (Level 1), 117 local emergency medical centres (Level 2), and 119 local emergency medical rooms (Level 3) in South Korea. From 2016 to 2018, 399 (99.5%) emergency medical institutions participated in the NEDIS data collection [16]. The information of patients who visited emergency departments (EDs) was sent from each ED to the National Emergency Medical Centre database in real-time.
In this study, all patients under 19 years of age with tra c accident injuries were identi ed. In South Korea, driving licenses for cars are permitted for individuals over 20 years old, whereas driving licenses for motorcycle are permitted for individuals over 16 years old. We included patients who rode two-wheel vehicles; pedestrians hit by bicycles were excluded.

Variables and outcome Measures
NEDIS collected demographic and clinical data: age, sex, ED visit date, ED visit time, geographic location of EDs, insurance types, helmet use, means of visit, consciousness of patients in ED, systolic blood pressure, diastolic blood pressure, pulse rate, respiratory rate, diagnosis of patient in the ED, injury severity score (ISS), and dispositions after ED care (discharge, transfer to other hospital, admission to general ward (GW), or intensive care unit (ICU)). In the case of admitted patients, the data of nal diagnosis and medical results on discharge were sent. We divided ED visit date for spring (March to May), summer (June to August), autumn (September to November), and winter (December to February). The time was divided into dawn (00:00 to 05:59), morning (06:00 to 11:59), afternoon (12:00 to 17:59), and night (18:00 to 23:59).
We analysed the nal diagnosis to categorise the injury (injury regions and fracture sites). Injury characteristics included the epidemiology and severity of injuries according to the Abbreviated Injury Scale (AIS) scores and Injury Severity Score (ISS) [17]. ED disposition, type of discharge on admission, duration of hospitalisation, and mortality were analysed as clinical outcomes.

Statistical Analysis
We compared and analysed the variables of the patients and injury-related characteristics between bicycle and motorcycle injuries. Categorical variables were analysed using the chi-square test. Student's t-test was used for continuous variables. We used the Statistical Package for the Social Sciences Statistics for Windows version 21 (International Business Machines Corporation, Armonk, NY, USA) for analyses, and 95% con dence intervals were considered statistically signi cant.

Results
From January 2016 to December 2018, the total number of two-wheel vehicle-related injuries under 19 population in the nationwide EDs included 37,410 bicycle-related cases and 16,932 motorcycle-related cases. (Figure 1) In the under-19 population, bicycle patients were distributed among all ages, with peaks at 12-13 years. Motorcycle patients were mainly over 14 years of age, peaking at the age of 17, and the age graph of motorcycle users was much steeper than that of bicycle users. Motorcycle users increased geometrically above the age of 16 because the license for motorcycles in South Korea is permitted from the age of 16 years. (Figure 2 (Table 1) The mean age of patients was 11.6 ± 4.0 years for bicycle injuries and 17.1 ± 1.9 years for motorcycle injuries. The incidence of injury was spring (30.4%), summer (36.3%), autumn (26.7%), and winter (6.6%) for bicycle injuries, and spring (24.2%), summer (28.3%), and autumn (27.9%), and winter (19.6%) for motorcycle injuries. Injury time was morning (3.7%), afternoon (11.4%), night (37.1%), and dawn (47.8%) for bicycle injuries and morning (20.9%), afternoon (8.5%), and night (20.6%), and dawn (50.1%) for motorcycle injuries. The use of helmets was 10.3% among patients with bicycle injuries and 46.7% among those with motorcycle injuries. Among the patients with bicycle-related injuries, 71.9% were treated with National Health Care Insurance, while 69.6% of those with motorcycle-related injuries were treated with tra c accident insurance. Amongst the patients, 25.1% of patients with bicycle injuries visited the ED by emergency call, while 62.0% of the patients with motorcycle injuries visited the ED by emergency call. Both bicycle and motorcycle accidents occurred more frequently in the urban areas (bicycle, 73.7%; motorcycle, 69.8%) than in the rural areas (bicycle, 26.3%; motorcycle, 30.2%). About 0.4% of bicycle injuries were alerted consciousness, while 3.2% of motorcycle injuries were alerted consciousness.

Comparison of injury patterns and clinical outcomes of patients under 19 years of age who visited the EDs with
two-wheel vehicle related injury (Table 2) Bicycle and motorcycle-related injuries were categorised according to AIS regions. There were 37,410 bicycle-related injuries recorded in the EDs. Of them, 6,316 (16.9%) patients had head and neck injuries, 2,492 (6.7%) had face injuries, 1189 (3.2%) had chest injuries, 272 (0.7%) had abdomen and pelvis injuries, 21,144 (56.5%) had external injuries, 12,127 (32.4%) had upper extremities injuries, 11,161 (29.8%) had lower extremities injury, and 449 (1.2%) had spine injuries.
The mean ISS score was 5.0 ± 6.1 in bicycle injuries and 9.0 ± 10.4 in motor injuries (P < 0.000). ISS >16 was 2,172 (5.8%) patients with bicycle injuries and 30,278 (18.0%) with motorcycle injuries (P < 0.000). This indicates that motorcycle injuries had a higher number of severe injuries that needed hospitalisation than bicycle injuries.

Disposition of ED in bicycle injuries
3.3. Injury patterns and clinical outcomes of patients who were hospitalised with two-wheeled vehicle related injury (Table 3) We analysed two-wheel vehicle related injury patients who were hospitalised in the ICU and GW. There were 3,346 bicycle injuries and 4,096 motorcycle injuries.
The mean ISS score for hospitalised patients was 12.0 ± 12.6 for bicycle injury and 17.6 ± 15.4 for motorcycle injury.
ISS >16 was observed in 922 (27.6%) hospitalised patients after bicycle accident and 1,850 (45.2%) hospitalised patients after motorcycle accidents. The mean length of hospital stay (LOS) was 191.5.8 ± 224.2 hours for bicycle injury, while the mean LOS was 359.6 ± 416.7 hours for motorcycle injury. There were 6 (0.2%) hospital mortality cases with bicycle injury and 49 (1.2%) with motorcycle injury.

Discussion
This is the rst nationwide study that analysed the characteristics of two-wheel vehicle injuries and clinical outcomes in individuals younger than 19 years in South Korea. This population-based study using the National Emergency Department Information System (NEDIS) evaluated the difference between bicycle-and motorcycle-related injuries presenting to EDs in South Korea between 2016 and 2018. This retrospective study presented the incidence of injury and fracture sites as well as the demographic characteristics of patients, and also categorised the injury region according to AIS and calculated ISS for all adolescent patients who visited the ED. We separately analysed the hospitalised patients' injury sites, fracture sites, ISS, and hospital length of stay. Previous studies have mainly focused on individual studies of bicycle or motorcycle crashes, or comparative studies targeting the elderly [8,18], but this study compared the results of bicycle and motorcycle injuries among adolescents.
The Road Safety Report showed the road death by age group in 2018, which showed that the number of road deaths fell by 28% among 0-20 year-olds after road safety improvements [19]. Compared to other international road tra c and accident databases, adolescents have a relatively low mortality rate on Korean roads. Mortality rates ranged from 0.6 for 0-14 years to 3.7 for 21-24 years old. This may be because young people in Korea tend to drive late. In Korea, individuals above the age of 20 years can obtain driver's license for car; however, a motorcycle license is available from the age of 16 years. In this study, it can be seen that the rate of bicycle accidents and motorcycle accidents decreased and increased, respectively, when the patient age exceeded 15 years. After obtaining a motorcycle license, teenagers enjoy riding motorcycles rather than bicycles, which leads to them experiencing motorcycle-related injuries that are more severe than bicycle-related ones.
South Korea has four seasons, and this study shows that accidents occurred frequently from spring to autumn and decreased in winter. This may be due to the reduced use of two-wheel vehicles due to weather-related hinderances in winter compared to other seasons. Night and dawn periods had a large proportion of two-wheel vehicle accidents. The lack of light at night may make it di cult for other cars to notice two-wheeled vehicles or for drivers of two-wheeled vehicles to see the road surface or structures clearly [20]. In addition, there may also have been many accidents caused by drunk-driving at night and dawn. A previous study of alcohol-related motorcycle accidents also showed that the incidences of accidents due to drunken driving motorcycles were high at night and dawn [21].
Although there have been many previous studies that have proven the protective effects of helmets [22,23], this study showed that only 10% of bicycle-injured and less than 50% of motorcycle-injured patients used helmets. A previous study on bicycle-related injury in the ED in South Korea during 2012-2014 showed that the use of helmet was nearly 20% [18], but decreased in 2016-2018 during the current study period. The helmet use rate of motorcycles was 85% in 2018 surveyed by the Korea Road Tra c Authority (KoROAD). There was a large difference between KoROAD and this study in the ratio of individuals wearing helmets. There are two possible reasons for this. The rst is that KoROAD's measurements were based on the road around tra c accident cases or on speci c samples. The second reason is that this study may not re ect the overall helmet usage rate in the population as we only considered the helmet usage rate of patients using two-wheeled vehicles who visited the ED after injury. [19] If the actual motorcycle rider's helmet wearing rate was 85%, the helmet usage rate of the injury group visiting the ED was very low.
This study showed that 86.8% of bicycle-related injuries and 94.9% of motorcycle-related injuries were in males.
Previous studies have shown that men had a higher proportion of injuries than females [24][25][26].
An ISS greater than 16 was more frequent in motorcycle than bicycle injuries, which means more severe injuries that need to be hospitalised in motorcycle injuries. We analysed two-wheeled vehicle related injury patients who were admitted to the ICU and GW. Bicycle injuries had more upper extremity injuries than motorcycle injuries. (32.4% vs.

76.0%).
There was a report about the orthopaedic characteristics of bicycle injury in South Korea. It revealed that fractures of the forearm and shoulder were the most common orthopaedic injuries. This was a study of the entire age of a single institution [27]. The majority of childhood tra c accidents were mild and required only minor treatment [26]. In this study, there was a low mortality rate. However, motorcycle mortality was 7 times higher than that of bicycle injuries. We investigated both the disposition and clinical outcomes at both points during discharge from the ED and discharge after hospitalisation. The reason was that it was di cult to determine the overall mortality rate and the injury that would require hospitalisation if only the ED was reported. The national data used in this study were transmitted upon evacuation from the ED and upon discharge after hospitalisation. The average ISS was higher for motorcycle-related injuries, and patients with ISS > 16 were higher as well. This means that even if the same region is injured, the severity is higher in motorcycle-related accidents. Patients with motorcycle accidents were more severe than bicycles, so hospital LOS and mortality rates were also higher. Comparing the entire patient visiting the ED with the hospitalised patient, the frequency order of the injured area was different. Many of the hospitalised patients were injured in the head and neck, face, and lower extremities. These injuries require hospitalisation and affect the increase in ISS. Lower extremity injury was higher in motorcycle accidents than in bicycle accidents. It could have a negative impact on return We could suggest some bene cial ideas to adolescents who ride two-wheel vehicles, depending on our study. In South Korea, helmets have become compulsory for users of all motorised two-wheelers since 2007. Head and neck injuries may require hospitalisation and have a poor prognosis. However, the rate of wearing a helmet on motorcycles and bicycles have been low. Helmets should be recommended and mandatory for both bicycle and motorcycle riders. In addition, two-wheel vehicle riders are recommended to use body protectors. Upper and lower extremity injuries were the most common injuries, so using arm, knee, and joint protectors may help to prevent extremity fractures. In addition, since most patients visit the ED at night, wearing protective gear with re ective lighting may help to prevent two-wheel vehicle crashes.
There are some limitations to our study. In this study, information on weather and road types were not taken into consideration. These factors could have affected the severity of injury. We also had no information on the patients' medical history and other laboratory tests that could affect the patient's outcome. Another limitation is that we did not investigate whether motorcycle usage was for leisure or livelihood. Information on several known and potential risk factors that could affect the severity, such as the speed at the time of the accident, the location of the accident, the weather, the license acquisition status, and engine displacement, could not be obtained. In addition, mopeds on the bike are not coded separately but are coded as bikes. Moreover, minor injuries could be treated at the outpatient clinic outside the ED, so this study could not represent all of the two-wheel vehicle injuries.

Conclusions
In the under 19 population, two-wheeled vehicle-related injuries had a very low mortality rate and occurred predominantly among males. Motorcycle injuries increased dramatically among individuals aged over 16 years, which is the required age for obtaining a license, and had a higher ISS (> 16), intensive care unit admission rate, and mortality rate than bicycle injuries. Bicycle accidents predominantly caused upper limb fractures, whereas motorcycle accidents predominantly caused lower limb fractures. Injuries in adolescents may have long-lasting physical and psychological problems. Preventive measures according to the means and the age group are required. In order to reduce injuries, adequate education regarding accidents and the importance of wearing protective devices should be provided to the youth when they obtain a motorcycle license.

Declarations Ethics approval
This study was approved by the Institutional Review Board (IRB) of Ewha Womans' University Mok-dong hospital (IRB No. 2020-11-034) and was approved by the ethical principles of the Declaration of Helsinki. Informed consent was waived by the IRB because the study was retrospective in nature and patient information was anonymised before the analysis.
Consent to publish NA Availability of data and materials The datasets used and/or analysed during the current study available from the corresponding author on reasonable request.

Competing interests
The authors declare that they have no competing interests.

Funding
This work was supported by the Center of National Emergency Medical Center. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.