Rethinking bicycle helmets as a preventive tool: a 4-year review of bicycle injuries
- 648 Downloads
Traumatic brain injury is a leading cause of disability in bicycle riders. Preventive measures including bicycle helmet laws have been highlighted; however, its protective role has always been debated. The aim of this study was to determine the utility of bicycle helmets in prevention of intra-cranial hemorrhage. We hypothesized that bicycle helmets are protective and prevent the development of intra-cranial hemorrhage.
We performed a 4-year (2009–2012) retrospective cohort analysis of all the patients who presented with traumatic brain injury due to bicycle injuries to our level 1 trauma center. We compared helmeted and non-helmeted bicycle riders for differences in the patterns of injury, need for intensive care unit admissions and mortality.
A total of 864 patients were reviewed of which, 709 patients (helmeted = 300, non-helmeted = 409) were included. Non-helmeted bicycle riders were more likely to be young (p < 0.001) males (p = 0.01). There was no difference in the median ISS between the two groups (p = 0.3). Non-helmeted riders were more likely to have a skull fracture (p = 0.01) and a scalp laceration (p = 0.01) compared to the helmeted riders. There was no difference in intra-cranial hemorrhage between the two groups (p = 0.1). Wearing a bicycle helmet was not independently associated (p = 0.1) with development of intra-cranial hemorrhage.
Bicycle helmets may have a protective effect against external head injury but its protective role for intra-cranial hemorrhage is questionable. Further studies assessing the protective role of helmets for intra-cranial hemorrhage are warranted.
KeywordsHelmet laws Traumatic brain injury Bicycle injury
According to the Center for Disease Control and Prevention (CDC), each year more than 500,000 people in the United States (US) are treated in emergency departments and more than 700 people die as a result of bicycle-related injuries . Traumatic Brain Injury (TBI) continues to remain the leading cause of death and disability after bicycle-related accidents across all age groups [1, 2, 3, 4, 5].
The changing demographic patterns across the US have promoted the use of bicycles among all age groups as means of daily transportation as well as for therapeutic and recreational activities [1, 2, 3, 4]. Given the increasing use of bicycles among individuals, several states have established legislations requiring mandatory use of helmets while riding a bicycle . The basis of these legislations is based on the findings of several studies that have highlighted the protective role of bicycle helmets in preventing head injury [6, 7, 8, 9, 10, 11, 12, 13, 14, 15]. However; these studies have assessed the protective benefits of helmets on development of external head injury and facial injury [14, 15]. The role of helmets in preventing the development of intra-cranial hemorrhage still remains controversial.
The aim of this study was to determine the utility of bicycle helmets in preventing development of intra-cranial hemorrhage. We hypothesized that bicycle helmets are protective and prevent the development of intra-cranial hemorrhage.
After the approval of the Institutional Review Board at the University of Arizona, College of Medicine, we performed a 4-year (2009–2012) retrospective cohort analysis of all trauma patients who presented to our level 1 trauma center after a bicycle accident.
Patients with recorded information of protective device and an initial head computed tomography (CT) scan were included. Patients transferred from other institutions, patients with missing data of protective devices, and patients dead on arrival were excluded from our study.
We collected the following data points from the patient’s electronic medical record: demographics (age, gender, race), physiologic parameters on presentation which included systolic blood pressure (SBP), heart rate (HR), temperature, and Glasgow Coma Scale (GCS) score, details of the bicycle accident (date, time, location, speed), information regarding the use of protective devices, physical examination findings on presentation, initial head CT scan findings, neurosurgical intervention details (craniotomy, craniectomy), hospital and intensive care unit (ICU) length of stay, and in-hospital mortality. The Injury Severity Score (ISS) and the Abbreviated Injury Scale (AIS) score were obtained from the trauma registry.
We then categorized patients into two groups: helmeted and non-helmeted group. The two groups were compared for demographics, patterns of head injury, ICU admission, discharge disposition, and mortality. The primary outcome measure was development of intra-cranial hemorrhage. The secondary outcome measure was requirement of ICU admission and in-hospital mortality. We defined intra-cranial injury as development of skull fracture and/or intra-cranial hemorrhage. The initial head CT scans were reviewed by the on-call radiologist and the findings were confirmed by a single investigator (trauma surgeon).
Data are reported as mean ± standard deviation for continuous variables, median (range) for ordinal variables, and proportions for categorical variables. We assessed the differences within the two groups utilizing the Students t test for parametric variables, Mann–Whitney U test for non-parametric variables, and Chi-square test for categorical variables. We performed univariate analysis to assess for the factors associated with development of intra-cranial head injury. Factors with p value ≤0.2 were used in a multivariate regression analysis for assessing independent factors associated with intra-cranial head injury. p value <0.05 in the multivariate regression analysis was considered to be statistically significant.
Helmeted (n = 300)
Non-helmeted (n = 409)
Age, y (mean ± SD)
32.2 ± 19.2
44.3 ± 19.1
ED GCS, median (IQR)
ED systolic BP, mean ± SD
129.8 ± 78
121.7 ± 61.4
ED heart rate, mean ± SD
93.8 ± 48.2
96.4 ± 51.6
Speed at accident, mean ± SD
20.8 ± 12.6
22.5 ± 12.5
Type of accident
Accident with another bicycle (%)
Accident with a motor vehicle (%)
Head AIS, median (IQR)
ISS, median (IQR)
Physical examination and initial CT scan findings
Helmeted (n = 300)
Non-helmeted (n = 409)
Scalp laceration, % (n)
Skull fracture, % (n)
Facial fractures, % (n)
Cervical spine fracture, % (n)
Intra-cranial hemorrhage, % (n)
Helmeted (n = 300)
Non-helmeted (n = 409)
Hospital admission, % (n)
Hospital LOS, mean ± SD
5.4 ± 3.6
5.3 ± 3.3
ICU admission, % (n)
ICU LOS, mean ± SD
3.1 ± 1.9
3.9 ± 1.1
Mortality, % (n)
Regression analysis for factors associated with intra-cranial hemorrhage
Unadjusted OR (95 % CI)
Adjusted OR (95 % CI)
Speed at accident
Type of accident
The protective role of bicycle helmets for development of intra-cranial injury remains unclear [6, 13, 14, 15]. In our study we found that, wearing a helmet was not independently associated with development of intra-cranial hemorrhage. Although we found that, helmeted bicycle riders were less likely to develop skull and facial fractures, there was no difference in the development of intra-cranial hemorrhage between helmeted and non-helmeted riders. The results of our study question the protective effects of helmets and advocate redesigning helmets that are protective against both external and internal head injury.
Bicycle helmets have been shown to be protective against the development of head injury which has resulted in the development of legislations mandating the use of helmets . In the United States, over 21 states have state-wide legislation warranting the use of bicycle helmets . Additionally; the Center for Disease Control and Prevention also recommends the use of bicycle helmets to prevent development of head injury . However, these recommendations are based on findings of studies showing the beneficial effects of helmets against the development of only external head injury [6, 7, 8, 9, 10, 11, 12, 13, 14, 15]. Our study provides evidence questioning the protective effect of helmets for development of intra-cranial injury.
Several studies have assessed the role of bicycle helmets for development of head injury [6, 7, 8, 9, 10, 11, 12, 13, 14, 15]. In our study, we found that, wearing a helmet was not independently associated with development of intra-cranial hemorrhage. Shafi et al.  in a retrospective review of bicycle riders highlighted no effect of helmets on development of intra-cranial injury. In another study, Wasserman et al.  also found that helmets were not protective against intra-cranial injury among bicycle riders. Contrastingly, Bambach et al.  demonstrated the protective effects of helmets for development of intra-cranial injury. In another meta-analysis of 16 studies, Attewell et al.  concluded that, helmets were protective against development of intra-cranial injury. However, these studies focused on a subset of riders with motor cycle accidents and included studies from various countries across the world. Given the variability in the type and standards of helmet development across different countries, we believe that the results of these studies are not generalizable.
In our study we found that, bicycle riders were less likely to have a scalp laceration, skull fracture, and a facial fracture compared to non-helmeted bicycle riders. Several studies have shown findings similar to our study and demonstrated the protective effects of helmets against development of external head injury and facial injury [6, 7, 8, 9, 10, 11, 12, 13]. Field tests and laboratory studies have also shown similar findings highlighting the protective role of helmets in developing external head and facial injury [8, 9, 10, 11, 12, 13]. We believe that, further research is required to clarify the protective role of helmets against development of intra-cranial hemorrhage. Additionally, redesigning of helmets is required to provide complete protection against both external and internal head injury.
Studies have demonstrated younger intoxicated males to be more likely involved in bicycle accidents and not wearing a helmet [8, 9, 12, 13]. In our study, we found that young and intoxicated bicycle riders were more likely to have an intra-cranial head injury after a bicycle accident. We believe that focused management and intervention are warranted in young bicycle riders under the influence of alcohol given the higher incidence of intra-cranial head injury.
The results of our study should be interpreted with the inherent limitations of a retrospective study design with a small sample size. Second, we did not take into account the type of helmet or bicycle the patients were riding. Despite these limitations, we demonstrated that there was no difference in the development of intra-cranial injury between helmeted and non-helmeted bicycle riders. The results of our study question the protective effect of helmets against development of intra-cranial head injury.
Bicycle helmets may have a protective effect against external head injury but, its protective role for intra-cranial injury needs further investigation. Appropriate measures to promote injury prevention programs aimed at safe bicycle riding should be enforced.
Conflict of interest
The authors Bellal Joseph, Viraj Pandit, Bardiya Zangbar, Mustafa Amman, Mazhar Khalil, Terence O’Keeffe, Tahereh Orouji, Anum Asif, Abdullah Katta, Daniel Judkins, Randall S. Friese, and Peter Rhee declare no identifiable conflict of interest.
This study has been approved by the Institutional Review Board at the University of Arizona, College of Medicine and this human study has been approved by the appropriate ethics committee and has therefore been performed in accordance with the ethical standards laid down in the 1964 Declaration of Helsinki and its later amendments.
- 1.Centers for Disease Control and Prevention. Web-based Injury Statistics Query and Reporting System (WISQARS). Atlanta: Centers for Disease Control and Prevention, National Center for Injury Prevention and Control. http://www.cdc.gov/injury/wisqars. Accessed 03 August 2013.
- 4.National Highway Traffic Safety Administration. Traffic safety facts, 2010 data—bicyclists and other cyclists. Washington, DC: US Department of Transportation; 2012. (publication no. DOT HS 811 624).Google Scholar
- 5.Bicycle Helmet Safety Institute. Helmet laws for bicycle riders. http://www.bhsi.org/mandator.htm. Accessed 5 October 2013.
- 8.Persaud N, Coleman E, Zwolakowski D, Lauwers B, Cass D. Nonuse of bicycle helmets and risk of fatal head injury: a proportional mortality, case–control study. CMAJ 2012;184(17).Google Scholar
- 15.Wasserman RC, Buccini RV. Helmet protection from head injuries among recreational bicyclists. Am J Sports Med. 1990;18(1):96–7.Google Scholar
- 16.Centers for Disease Control and Prevention. Nonfatal traumatic brain injuries related to sports and recreation activities among persons aged ≤19 years—United States, 2001–2009. Morb Mortal Wkly Rep. 2011;60(39):1337–42.Google Scholar