Bicycling is a popular recreational activity and means of transportation among people of all ages. A national survey by the Outdoor Foundation in 2013 identified bicycling as the most popular outdoor activity among U.S. children and the third most popular among U.S. adults . Although various personal and structural safeguards have been studied and implemented, data from the Centers for Disease Control and Prevention (CDC) show that cycling-related injuries still send half a million people to the emergency room and cause 900 fatalities every year . Furthermore, reported numbers likely underestimate the true incidence of bicycle injuries, because not all injuries are documented in police or hospital records. Children are the most commonly injured age group, but the elderly sustain injuries with higher morbidity and mortality . This suggests that bicycle injury patterns may vary with demographic and behavioral factors, and that prevention strategies can be differentially adjusted for each target population.
Current injury prevention methods include protected bicycle lanes, cyclist visibility, cyclist education, and protective equipment (eg, helmets) . Of these, helmet use is by far the most extensively studied and commonly recommended. Many cities and states have enacted local helmet laws, most of which are limited to riders under the age of 18 . These laws have been controversial, with one side citing the number of studies indicating reduction of head injury and mortality with helmet use, and the other side pointing out the lack of high quality evidence that show helmet laws can effectively change injury patterns without also decreasing ridership [5-7]. Compliance with helmet-wearing is low, as low as one quarter of cyclists, which is especially true among young riders [8-9].
Many studies on bicycle ridership have previously identified risk factors for injury and mortality [3,10-15]. Additionally, other studies have focused on helmets, examining rates of, barriers to, and effectiveness of helmet use [3,8-9,16-18]. Yet, despite the published research and public reports, bicycle injuries have not seen a dramatic decline. Understanding factors associated with cycling-related injury severity and mortality may potentially help establish effective policy countermeasures. More importantly, further research can bring awareness to this ongoing issue that is both deadly and costly. The objectives of the current study were to examine cycling-related injuries from both local and national trauma databases and identify cyclist- and injury-related risk factors, and to compare the two sets of results to determine whether guidelines for bicycle safety can be adjusted for local communities.
PATIENTS & METHODS
The National Trauma Data Bank (NTDB) and a local Level I trauma center database were separately queried for bicycle injury data from January 2007 to December 2012. NTDB is managed by the American College of Surgeons and contains prospectively collected, de-identified data from over 700 trauma centers across the USA. The local trauma database contains similar information and contributes data annually to the NTDB. Approval was obtained from the University of Texas Medical Branch’s Institutional Review Board for this patient population.
Patients with bicycle-related injuries were retrospectively identified using ICD-9 E-codes (800-807[.3], 810-825[.6], 826.1). All external causes in which the patient was a bicyclist, such as collisions with motor vehicles, were included. Each bicycle trauma event was considered independently, even if a patient was involved in more than one accident during the study period. Patient characteristics (demographics, drug use), injury factors (mechanism, location, body region, helmet use), and short-term outcomes (severity, complications, number of procedures, length of stay, death) of interest were extracted. Patients under the age of 3 were excluded due to low likelihood of independent riding.
Data sets from the 2 databases were separately analyzed and then compared. Univariate analyses were carried out to describe each variable, using means (standard deviations) or proportions, as appropriate. Bivariate categorical comparisons were performed using the Pearson Chi-square test or Fisher’s exact test. Groups were compared using the Student’s t-test or analysis of variance (ANOVA). Multivariate models (logistic regressions) were built based on the bivariate analyses in order to relate predictor variables to outcome variables and control for confounding variables. In general, the variables with a bivariate analysis P-value <0.2 were included in the multivariate models. Odds ratios were determined for each predictor variable in the multivariate analyses. All tests were two-sided, and a P-value <0.05 considered significant. All analyses were completed using the R statistical package version 3.2.5 (R Developmental Core Team; R: A Language and Environment for Statistical Computing, 2009; available from: http://www.R-project.org).
National Database Summary
The NTDB query identified 113,623 bicycle trauma event evaluations in the years 2007-2012. Males made up 80% of injury evaluations (Table 1). The average patient age was 32.8 years (range 3-89). There was a 7:1:1 White:Black:Hispanic ratio. Of those patients whose alcohol and drug usage status were recorded (92,561 and 86,649, respectively), 9.7% were found to be using alcohol above the legal limit, and 9.2% were found to be using either illegal drugs or using prescription drugs illegally. Among the injured cyclists whose helmet status was recorded (92,209 incidents), 32% reported wearing helmets.
Motor vehicle accident was the mechanism behind 34% of injury evaluations, while bicycle-only accident was behind 64% of injuries identified. The most common location for injury was on the street (72%), and the second most common was recreation areas (10%). The average Injury Severity Score (ISS) was 9.8 (SD=8.3, range 1-75), and the mortality (at arrival and/or post-admission) was 1.9%. Average length of stay was 3.9 days (SD=7.1, range 0-314).
Head and neck injuries occurred in 65,413 (57.6%) injury evaluations, and traumatic brain injuries occurred in 48,317 (42.5%; Table 2). Fractures, the most common injuries, were sustained by 66% of injured cyclists (Table 3).
Compared to helmeted cyclists, the non-helmeted cyclists were younger, used more alcohol and illegal drugs, and were disproportionately male, Hispanic or non-Hispanic black, and Medicaid-insured (p<0.001; Table 4). Non-helmeted cyclists also suffered higher rates of head and neck injuries, traumatic brain injuries, and mortality (p<0.001).