Article, Traumatology

Preventive effects of motorcycle helmets on intracranial injury and mortality from severe road traffic injuries

a b s t r a c t

Introduction: Road traffic injuries caused by motorcycle crashes are one of the major public health burdens lead- ing to high mortality, functional disability, and high Medical costs. The helmet is crucial protective equipment for motorcyclists. This study aimed to measure the protective effect of motorcycle helmets on clinical outcomes and to compare the effects of high- and low-speed motorcycle crashes.

Methods: A cross-sectional observational study was conducted using a nationwide registry of severe trauma pa- tients treated by emergency medical services (EMS) providers in Korea. The study population consisted of severe trauma patients injured in motorcycle crashes between January and December 2013. The primary and secondary outcomes were Intracranial injury and in-hospital mortality. We calculated adjusted odds ratios (AORs) of hel- met use and motorcycle speeds for study outcomes after adjusting for potential confounders.

Results: Among 495 eligible patients, 105 (21.2%) patients were wearing helmets at the time of the crash, and 256 (51.7%) patients had intracranial injuries. The helmeted group was less likely to have an intracranial injury com- pared with the un-helmeted group (41.0% vs. 54.6%, AOR: 0.53 (0.33-0.84)). However, there was no significant difference in in-hospital mortality between the two groups (16.2% vs. 16.9%, AOR: 0.91 (0.49-1.69)). In the inter- action analysis, there was a significant preventive effect of motorcycle helmet use on intracranial injury when the speed of the motorcycle was b 30 km/h (AOR: 0.50 (0.27-0.91)).

Conclusion: Wearing helmets for severe trauma patients in motorcycle crashes reduced intracranial injuries. The preventive effect on intracranial injury was significant in low-speed motorcycle crashes.

(C) 2017

Introduction

Road traffic injuries are a major Public health problem in both devel- oped and Developing countries and are the sixth most common cause of death according to the World Health Organization (WHO) [1,2]. Motor- cycle drivers are vulnerable road users, as motorcyclists are 34 times more likely to die from road traffic injuries than those who drive other vehicles, and there is an 8-fold higher risk of being injured per vehicle mile [3]. However, motorcycles are accepted as inexpensive, conve- nient, and fuel-efficient means of transportation, and their use is in- creasing in many countries. In Korea, more than half of motorcycles are used to deliver parcels or food. According to the survey conducted by the Korea Research Institute for the Alternative Worker’s Movement,

* Corresponding author at: Laboratory of Emergency Medical Services, Seoul National University Hospital Biomedical Research Institute, 101 Daehak-Ro, Jongno-Gu, Seoul 03080, Republic of Korea.

E-mail address: [email protected] (Y.S. Ro).

51% of postmen experienced Road traffic accidents, including motorcy- cle crashes. Motorcycle crashes accounted for approximately 5% of all road traffic injuries in Korea, and the case-fatality rate from motorcycle injuries was approximately 12%, which was higher than the 2.1% for all road traffic fatalities [4,5].

Traumatic brain injuries (TBIs) caused by motorcycle crashes are es- timated to be the leading cause of death in 50% of cases with fatalities [6]. TBI is also a catastrophic event that can destroy quality of life. Most patients who survive after intracranial injury remain cognitively impaired or have post-injury functional disability resulting in high med- ical costs [7]. There has been limited evidence of effective therapeutic interventions to improve long-term functional outcomes in patients who suffered a severe TBI. Therefore, primary Prevention efforts for TBI should be emphasized.

Helmets, which are crucial protective equipment for motorcyclists and bicyclists, significantly reduce the risk of TBI and case-fatality from motorcycle and bicycle crashes [8-10]. In terms of biomechanical efficacy, several simulation studies demonstrated that the preventive

http://dx.doi.org/10.1016/j.ajem.2017.07.044

0735-6757/(C) 2017

mechanism of helmet use is diffusing and attenuating the impact on the skull and brain resulting from the primary and secondary collisions [11-13]. High-speed motorcycle crashes increase the energy of the col- lision and the force transmitted to the human body. Faster motorcycle speeds may increase the risk of injury. There may be certain thresholds of motorcycle speeds for which the helmet is no longer able to compen- sate and the protective effect is lost. However, there are limited studies comparing the preventive effects of helmets on clinical outcomes in high- and low-speed motorcycle crashes.

We hypothesized that the preventive effects of a helmet on intracrani- al injury and case-fatality would be greater in magnitude for low-speed motorcycle crashes than for high-speed crashes among severe trauma pa- tients injured in a motorcycle crash. The aims of this study were to evalu- ate the protective effects of motorcycle helmets on clinical outcomes and to compare the effects across high- and low-speed motorcycle crashes.

Methods

Study setting

The total number of registered motorcycles in Korea was approxi- mately 2.1 million in 2015 (population is approximately 50 million). Wearing helmets for all motorcycle drivers and riders was mandated by the Road Traffic Act. In Korea, it is illegal to drive a motorcycle on a highway; therefore, all of the motorcycle crashes occur on the national highways, local roads, and county roads.

The emergency medical services (EMS) system in Korea is single- tiered, and the emergency medical technicians provide prehospital treatment for injured patients depends upon the patients’ needs [14]. There are approximately 460 emergency departments (EDs) in Korea that are designated level 1 through 3 by the Ministry of Health and Welfare based on capacity and resources. The level 1 (n = 20) and level 2 (n = 119) EDs must be staffed by emergency medicine specialists 24 h a day and 7 days a week by law and have more resources and better facilities for emergency care. The Ministry of Health and Wel- fare designated 7 regional trauma care centers to be staffed by trauma surgeons in 2013 to improve trauma care systems and to enhance clin- ical outcomes by avoiding Preventable death in severe trauma patients.

Study design and data source

This study was a cross-sectional observational study using a nation- wide registry of severe trauma patients treated by EMS providers in Korea. The EMS providers defined severe trauma as either a patient who had an abnormal Revised Trauma Score in the field or a pa- tient who met the criteria of the field triage decision scheme for trans- port to a trauma center designated by the American College of Surgeons Committee on Trauma (ACS-COT) and the guidelines for field triage of injured patients from the Centers for Disease Control and Prevention (CDC) [15,16].

Data on the national EMS-treated severe trauma registry was col- lected from EMS run sheets for basic ambulance operation information, EMS severe trauma registry for detailed environment and prehospital information, and the national severe trauma registry for hospital care and survival outcomes via hospital medical record review. EMS run sheets and the EMS severe trauma registry were abstracted from the EMS database of the National Emergency Management Agency (NEMA). A subsequent medical record review was performed using the medical records of each destination hospital by trained medical re- cord reviewers of the Korea Center for Disease Control and Prevention (KCDC). The national EMS-treated severe trauma registry covers metro- politan, urban and rural areas in Korea.

For quality assurance, monthly meetings were held by a project Quality management committee in the KCDC, which consisted of emer- gency physicians, epidemiologists, statistical experts, representatives from NEMA, and medical record review experts. The quality

management committee provided the standard operational protocols to extract the data from the medical records and provided consultation and feedback to the medical record reviewers as needed.

Study population

The study population included all severe trauma patients who were injured in a motorcycle crash and who were treated by EMS providers in 10 provinces between from January 2013 and December 2013. We in- cluded all occupants, both driver and passengers, older than 15 years who were injured in a 2-wheeled motorcycle crash. We excluded pa- tients who had cardiac arrest at the scene or who had unknown infor- mation on hospital outcomes.

Main outcomes

The primary outcome of the study was intracranial injury, which was defined as a diagnosis of ICD-10 code S06.1-S06.9 as recorded on discharge summaries after ED and hospital admission. The secondary outcome was in-hospital mortality, defined as death in the ED or during initial admission resulting from the injury regardless of the duration from injury to death, and it was determined at discharge from the ED or hospital. The tertiary outcome was intensive care unit (ICU) admis- sion. Emergency physicians in each hospital decided whether the pa- tient needed to be admitted to a general ward or ICU without a nationwide standard protocol.

Variables and measurements

The main exposure of interest was helmet use as indicated in the EMS-treated severe trauma registry. The helmet was defined as protec- tive equipment worn on the head with either full or partial coverage. We collected information on demographic factors (age and gender), in- jury-related factors (time of injury, place of injury, speed of motorcycle, and alcohol-related injury), Prehospital factors (EMS response time (from call to arrival at the scene), EMS prehospital time (from call to ar- rival at the ED), and prehospital care), and ED/hospital factors (level of ED, diagnostic assessment, medical treatment in the ED, Abbreviated In- jury Scale (AIS) score and Injury Severity Score (ISS), ED disposition, pa- tient outcome after admission if the patient was admitted, and Glasgow Outcome Scale at hospital discharge) from the registry. The speed of the motorcycle was categorized into high (>= 30 km/h) and low (b 30 km/h) as recorded by EMS providers based on interviews with vic- tims, witnesses, and police officers on the scene. The classification of motorcycle speed was based on the guidelines for field triage of injured patients from the ACS-COT and the CDC [15,16].

Statistical analysis

Descriptive analyses were performed to examine the distributions of the study variables. Counts and proportions were used for categorical variables, and medians and interquartile ranges were used for continu- ous variables. Categorical variables were compared using Chi-square tests, and continuous variables were compared using Mann-Whitney U tests. P-values were based on a two-sided significance level of 0.05.

Unadjusted and adjusted odds ratios (ORs) with 95% confidence in- tervals (CIs) for helmet use for the study outcomes were calculated using multivariable logistic regression analysis with no helmet use as the reference. The model adjusted for age, gender, speed of motorcycle, season of injury, time of injury and alcohol consumption.

To determine variability in the preventive effect of helmet use accord- ing to the different motorcycle speeds, we developed an interaction model with an interaction term between helmet use and motorcycle speed (helmet x speed of motorcycle) as the final multivariable logistic regression model for the study outcomes. All statistical analyses was per- formed using SAS software, version 9.4 (SAS Institute Inc., Cary, NC, USA).

Ethics statements

The study was approved by the Institutional Review Board of Seoul National University Hospital (IRB No. 1206-024-412).

Results

Among the 16,781 patients in the EMS-treated severe trauma regis- try, 892 patients were in motorcycle crashes. Cases younger than 15 years old (n = 9), patients who experienced cardiac arrest at the scene (n = 176) and patients who had unknown information on hospi- tal outcome (n = 212) were excluded (Fig. 1).

Table 1 shows the demographic characteristics by motorcycle hel- met use. Among the 495 eligible patients, 105 (21.2%) patients were wearing helmets when involved in the motorcycle crash. In terms of clinical outcomes, 51.7% of eligible patients had intracranial injuries, and 43.8% had an ISS of N 16. Additionally, 50.3% were admitted to the ICU, 1.8% were in a vegetative state, and 5.5% had severe disability at hospital discharge. The in-hospital mortality rate was 16.8%. The un-hel- meted group had a higher proportion of intracranial injury (54.6% vs. 41.0%, P b 0.01). However, there was no significant difference in in-hos- pital mortality (16.9% vs. 16.2%, P = 0.84).

Table 2 shows the demographic characteristics by intracranial injury. Patients without intracranial injury were more likely to wear motorcy- cle helmets than patients with intracranial injury (25.9% vs. 16.8%, P = 0.01). The proportion of high-speed motorcycle crashes was higher in patients with intracranial injuries than in those without intracranial in- juries (47.3% vs. 26.8%, P b 0.01).

The results from the Multivariable logistic regression models are shown in Table 3. The helmeted group was less likely to have intracra- nial injury and be admitted to the ICU after motorcycle crashes com- pared with the un-helmeted group (the adjusted ORs (95% CI): 0.53 (0.33-0.84) for intracranial injury and 0.47 (0.29-0.75) for ICU admis- sion), whereas there was no significant difference in in-hospital mortal- ity (the adjusted ORs (95% CI): 0.91 (0.49-1.69)). Low-speed motorcycle crashes were associated with reduced risk of intracranial in- jury, in-hospital mortality, and ICU admission.

In the interaction model in which the preventive effects of motorcy- cle helmets were estimated for different motorcycle speeds, there was a significant preventive effect of motorcycle helmet use on intracranial in- jury when the speed was b 30 km/h (the adjusted ORs (95% CI): 0.50 (0.27-0.91)), but there was no significant difference between the hel- meted group and the un-helmeted group in high-speed motorcycle crashes. Regarding in-hospital mortality and ICU admission, there

were no significant differences in the effects of motorcycle helmet use between low- and high-speed motorcycle crashes. The helmeted group was less likely to be admitted to the ICU compared to the un-hel- meted group in both low- and high-speed motorcycle crashes, and there was no significant difference in in-hospital mortality between the two groups regardless of speed (Table 4).

Discussion

The nationwide EMS-treated severe trauma registry data illustrated that wearing a helmet had significant protective effects on intracranial injury and ICU admission for motorcyclists after severe road traffic inju- ries. However, there was no significant reduction in in-hospital mortal- ity. Only one-fifth of the severe trauma patients suffering from motorcycle injuries were wearing helmets in this study, despite the legal requirement to wear a helmet for all motorcycle rider in Korea. The proportion of intracranial injury was as high as 54.6% in patients not wearing a helmet and 41.0% in those wearing a helmet. The protec- tive effect of the helmets on intracranial injury was preserved at speeds under 30 km/h. Our results emphasized that wearing a motorcycle hel- met is a strong intervention for preventing intracranial injuries after motorcycle crashes, especially when driving a motorcycle at a low speed.

Motorcycle helmets are an effective modality for motorcyclists to re- duce TBI from road traffic injury, as numerous pieces of evidence sup- port the association between wearing helmets and reduced case- fatality and health-related costs [7,10,17,18]. Among patients who sustained severe trauma in this study, motorcycle riders wearing a hel- met had 0.53 times lower odds of intracranial injury and 0.47 times lower likelihoods of ICU admission compared to those who did not wear a helmet. Intracranial injury is one of the most fatal anatomical re- gions for road traffic injuries and is known to cause consequent disabil- ity and negative sequelae [19,20]. However, motorcycle helmets had no statistically significant effect on in-hospital mortality. One speculative explanation for our finding is that the study population in this study was severe trauma patients treated by EMS providers, and therefore, the in-hospital mortality rate (16.8%) was higher than in previous stud- ies. The motorcycle helmet protects the face and head directly in case of accident while diffusing the impact caused by the primary and the sec- ondary collision. It has no effects on the thorax, abdomen, pelvis, or ex- tremities. Therefore, the motorcycle helmet would not have a preventive effect on fatalities mainly caused by injuries to other ana- tomical locations.

Fig. 1. Study population.

Table 1

Demographic characteristics of the study population by motorcycle helmet use.

Total Helmet No helmet P-value

N

%

n

%

n

%

Total Age

495

100

105

21.2

390

78.8

0.14

16-39

251

50.7

56

53.3

195

50.0

40-64

150

30.3

36

34.3

114

29.2

65 +

94

19.0

13

12.4

81

20.8

0.46

Year, median (IQR)

40 (23-59)

38 (29-55)

40 (22-60)

Gender

Male

454 91.7

103 98.1

351 90.0

Speed of motorcycle

High-speed

185 37.4

42 40.0

143 36.7

Alcohol

Intake

96 19.4

14 13.3

82 21.0

Season of injury

b0.01 0.53

0.08

0.90

Spring

119

24.0

28

26.7

91

23.3

Summer

170

34.3

34

32.4

136

34.9

Fall

127

25.7

27

25.7

100

25.6

Winter

Time of injury

79

16.0

16

15.2

63

16.2

0.06

Daytime Place of injury

Metropolitan

224

227

45.3

45.9

56

48

53.3

45.7

168

179

43.1

0.97

45.9

EMS time intervals

Response time, min

6 (5-9)

6 (5-9)

6 (5-9)

0.70

prehospital time, min

21 (16-29)

21 (17-32)

21 (16-29)

0.39

Prehospital care

Oxygen supply

327

66.1

68

64.8

259

66.4

0.75

spine immobilization

435

87.9

96

91.4

339

86.9

0.21

Bleeding control

262

52.9

51

48.6

211

54.1

0.31

Level of ED

b0.01

Level 1/2

374

75.6

99

94.3

275

70.5

Level 3

121

24.4

6

5.7

115

29.5

Clinical finding

Intracranial injury

256

51.7

43

41.0

213

54.6

0.01

Head, AIS >= 3

242

48.9

40

38.1

202

51.8

0.01

ISS >= 16

217

43.8

41

39.1

176

45.1

0.27

Operation

185

37.4

41

39.1

144

36.9

0.69

ED disposition

Admission to ward

111

22.4

34

32.4

77

19.7

b0.01

Admission to ICU

249

50.3

39

37.1

210

53.9

b0.01

In-hospital mortality

Total

83

16.8

17

16.2

66

16.9

0.84

ED

34

6.9

8

7.6

26

6.7

Ward or ICU

49

9.9

9

8.6

40

10.3

GOS at discharge

0.75

Death

83

16.8

17

16.2

66

16.9

Vegetative state

9

1.8

2

1.9

7

1.8

Severe disability

27

5.5

3

2.9

24

6.2

Moderate disability

86

17.4

20

19.1

66

16.9

good recovery

290

58.6

63

60.0

227

58.2

IQR: interquartile range; EMS: emergency medical services; ED: emergency department; AIS: Abbreviated Injury Scale; ISS: injury severity score; ICU: intensive care unit; GOS: Glasgow outcome scale.

The speed of a motorcycle is one of the main influences on clinical outcomes after road traffic injuries [21]. In this study, high-speed mo- torcycle crashes were associated with increased risks of intracranial in- jury, in-hospital mortality, and ICU admission compared to low-speed crashes. We hypothesized that there may be certain thresholds of mo- torcycle speeds for which the helmet is no longer able to compensate and the protective effect is lost. The high-speed motorcycle crashes modified the preventive effects of the motorcycle helmets on intracrani- al injury in this study; the preventive effects were maintained only in low-speed motorcycle crashes. High-speed involves strong forces that are transmitted to the human body at the time of a collision. Speed limits for motorcycles according to road function can increase road safe- ty and reduce the incidence of motorcycle crashes and the health bur- den resulting from road traffic injuries [22].

The public burden of motorcycle crashes is huge because motorcycle riders are relatively young and are vulnerable to road traffic injuries [20]. Wearing a motorcycle helmet and enforcing speed limits are

Table 2

Demographic characteristics of the study population by intracranial injury.

Total

Intracranial injury

No intracranial injury

P-value

N %

n %

n %

Total Helmet use

495 100

256 51.7

239 48.3

0.01

Helmet

Age

105 21.2

43 16.8

62 25.9

0.59

16-39

251 50.7

128

50.0

123

51.5

40-64

150 30.3

75

29.3

75

31.4

65 +

94 19.0

53

20.7

41

17.2

Gender

Male

454

91.7

237

92.6

217

90.8

0.47

Speed of motorcycle

High-speed

185

37.4

121

47.3

64

26.8

b 0.01

Alcohol

Intake

96

19.4

39

15.2

57

23.9

0.02

Prehospital care

Oxygen supply

327

66.1

205

80.1

122

51.1

b 0.01

Spine immobilization

435

87.9

242

94.5

193

80.8

b 0.01

Bleeding control

262

52.9

142

55.5

120

50.2

0.24

Level of ED

Level 1/2

374

75.6

220

85.9

154

64.4

b 0.01

Level 3

121

24.4

36

14.1

85

35.6

Clinical finding

ISS >= 16

217

43.8

176

68.8

41

17.2

b 0.01

Operation

185

37.4

126

49.2

59

24.7

b 0.01

ED disposition

Admission to ward

111

22.4

23

9.0

88

36.8

b 0.01

Admission to ICU

In-hospital mortality

249

50.3

211

82.4

38

15.9

b 0.01

Total

83

16.8

60

23.4

23

9.6

b 0.01

ED

34

6.9

18

7.0

16

6.7

Ward or ICU

49

9.9

42

16.4

7

2.9

GOS at discharge –

Death

83

16.8

60

23.4

23

9.6

Vegetative state

9

1.8

9

3.5

0

Severe disability

27

5.5

25

9.8

2

0.8

Moderate disability

86

17.4

29

23.1

27

11.3

Good recovery 290 58.6 103 40.2 187 78.2

IQR: interquartile range; EMS: emergency medical services; ED: emergency department; AIS: abbreviated injury scale; ISS: injury severity score; ICU: intensive care unit GOS: Glas- gow outcome scale.

important evidence-based strategies to reduce injury severity and case-fatality and to ultimately reduce the overall health burden of mo- torcycle crashes [22-25]. In this study, only 21.2% of patients severely in- jured in motorcycle crashes were wearing helmets despite the legislative measures to enforce helmet use, which was a very disheartening figure compared to previous studies [3,25-27]. In previ- ous studies in Korea, the rate of wearing a motorcycle helmet among pa- tients visiting the ED after motorcycle crashes, regardless of injury severity, varied from 60% to 70% [27,28]. The lenient fine and weakly enforced regulations for helmet use can affect the low compliance rate. Primary enforcement of motorcycle helmet laws and stronger law enforcement are required for effective regulation of motorcycle hel- met use. Extensive public advocacy campaigns, legislation, strong en- forcement of related laws, and engineering and development of new technology are necessary to enhance helmet use among motorcyclists [29].

Limitations

There are several limitations in this study. First, the study population consisted of EMS-treated severe trauma patients and excluded patients whose EMS providers evaluated the patient as a non-severe trauma in the field. There is a possibility of underestimation of the benefits of mo- torcycle helmets because the excluded population might be both biased towards using helmets and be the ones who had the greatest beneficial effect from using a helmet. Second, motorcycle helmet use, which was

Table 3

Logistic regression analysis of study outcomes by helmet and speed of motorcycle.

30 km/h or not); therefore, we could not compare the preventive effects of helmet use across different motorcycle speeds. Fourth, we could not

Total Positive

outcomes

Unadjusted Adjusted

distinguish whether the motorcycle rider was a driver or a non-driving passenger and whether or not there were non-driving passengers in the

N n % OR (95% CI) OR (95% CI)

Primary outcome: intracranial injury

Total 495 256 51.7

Helmet use

Helmet

105

43

41.0

0.58 (0.37-0.89)

0.53 (0.33-0.84)

No helmet

390

213

54.6

1.00

1.00

Speed of motorcycle

High-speed 185

121

65.4

1.00

1.00

Low-speed

310

135

43.5

0.41 (0.28-0.60)

0.37 (0.25-0.55)

Secondary outcome: in-hospital mortality

Total

495

83

16.8

Helmet use

Helmet

105

17

16.2

0.95 (0.53-1.70)

0.91 (0.49-1.69)

No helmet

390

66

16.9

1.00

1.00

Speed of motorcycle

High-speed

185

41

22.2

1.00

1.00

Low-speed

310

42

13.5

0.55 (0.34-0.89)

0.48 (0.29-0.80)

Tertiary outcome: ICU admission

Total

495

249

50.3

Helmet use

Helmet

105

39

37.1

0.51 (0.33-0.79)

0.47 (0.29-0.75)

No helmet

390

210

53.8

1.00

1.00

Speed of motorcycle

High-speed

185

115

62.2

1.00

1.00

Low-speed

310

134

43.2

0.46 (0.32-0.67)

0.43 (0.29-0.63)

Adjusted for age, gender, speed of motorcycle, season of injury, time of injury, place of in- jury, and Alcohol intake. OR: odds ratio; CI: confidence interval; ICU: intensive care unit.

the main exposure variable, was measured by medical record review. Furthermore, we did not collect information on which type of motorcy- cle helmet the patients wore at the time of the motorcycle crash, wheth- er the helmet was worn appropriately, or where the helmet was certified. There is a possibility of misclassification and/or over- or under-estimation, which can result in bias. Third, the speed of the mo- torcycle was recorded by an EMS provider through face-to-face inter- views with patients, guardians, witnesses, or police officers. We collected the information as a dichotomous variable (faster than

Table 4

Interaction effects of helmet use with speed of motorcycle.

Outcome/total Adjusted

n/N (%) OR (95% CI)

Primary outcome: intracranial injury High-speed

Helmet 23/42 (54.8) 0.58 (0.28-1.18)

No helmet 98/143 (68.5) 1.00

Low-speed

Helmet 20/63 (31.7) 0.50 (0.27-0.91)

No helmet 115/247 (46.6) 1.00

Secondary outcome: in-hospital mortality High-speed

Helmet

8/42 (19.0)

0.75 (0.30-1.86)

No helmet

33/143 (23.1)

1.00

ow-speed

Helmet 9/63 (14.3) 1.08 (0.47-2.47)

No helmet

33/247 (13.4)

1.00

L

Tertiary outcome: ICU admission High-speed

Helmet

19/42 (45.2)

0.42 (0.21-0.86)

No helmet

Low-speed

96/143 (67.1)

1.00

Helmet

20/63 (31.7)

0.50 (0.28-0.92)

No helmet

114/247 (46.2)

1.00

Adjusted for age, gender, helmet, speed of motorcycle, season of injury, time of injury, place of injury, alcohol intake, and interaction term (helmet x speed of motorcycle). OR: odds ratio; CI: confidence interval; ICU: intensive care unit.

vehicle. Injury-related information on the specific position, cause of the crash, mechanism of the collision, and blood alcohol level were limited and not fully adjusted. Fifth, we did not collect information on long- term hospital outcomes, such as disability.

Conclusion

The findings from this study reiterate the importance of wearing hel- mets to reduce intracranial injuries for motorcyclists suffering from se- vere road traffic injuries. Among severe trauma patients injured from motorcycle crashes, wearing a helmet had preventive effects on intra- cranial injury and ICU admission. Public health efforts and multidisci- plinary approaches are needed to increase motorcycle helmet use and can help reduce the health burden of motorcycle crashes.

Funding acknowledgement

This study was financially supported by the Korea Centers for Dis- ease Control and Prevention (2014) (Grant No. 2014-E33011-00). The funders had no role in study design, data collection and analysis, deci- sion to publish, or preparation of the manuscript.

Disclosure

The authors declare no conflicts of interest, and the authors are re- sponsible for the content and writing of the article.

Author contributions

Dr. Ro had full access to all of the data in the study and take respon- sibility for the integrity of the data and the accuracy of the data analysis.

Study concept and design: Drs. Ro, Kim, Shin.

Acquisition, analysis, or interpretation of data: Drs. Ro, Kim, Song, Hong, and Jeong.

Drafting of the manuscript: Drs. Ro and Kim. Critical revision of the manuscript for important intellectual content:

Dr. Shin.

Statistical analysis: Drs. Ro and Kim. Obtained funding: Dr. Shin.

Administrative, technical, or material support: Drs. Kim, Song, Hong, and Jeong.

Study supervision: Drs. Shin.

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