Cycling crashes: factors associated with head trauma, alcohol consumption and helmet use Chiara Orsi a, Ottavia E. Ferraro a, Cristina Montomoli a, Dietmar Otte b, Anna Morandi a a Centre of Study and Research on Road Safety, Section of Biostatistics and Clinical Epidemiology, Department of Public Health, Experimental and Forensic Medicine, University of Pavia, Italy b Accident Research Unit, Hannover Medical University, Germany Abstract Cycling is becoming one of the most common modes of transportation across the entire world, due to its simplicity, low cost, and health-related benefits. In a road crash, however, cyclists are among the most vulnerable road users and they can suffer more severe consequences compared to users of motorised vehicles. Alcohol consumption is a risk factor for being involved in a crash and for the consequences of a crash. Few studies have analysed the role of alcohol in bicycle crashes and the corresponding severity of outcome. The aim of this study is to evaluate which cyclist and crash characteristics are associated with alcohol consumption among cyclists who have been involved in a crash. The data source is the German In-Depth Accident Study database. All cyclists that were involved in a road crash between 2000-2010 and on whom an alcohol test was conducted were selected. A logistic regression analysis was carried out to evaluate the association between the rider s blood alcohol level (<0.05 mg/l vs 0.05 mg/l) and cyclist and accident characteristics. Female bicycle riders were less likely to have consumed alcohol compared to men (OR=0.23, CI=0.08-0.66); cyclists who did not wear a helmet were more likely to have consumed alcohol (OR=2.41, IC=1.08-5.38); cyclists who were not responsible for causing the road crash were less likely to have consumed alcohol compared to cyclists who were partially responsible (OR=0.22, CI: 0.08-0.61). Cyclists who were involved in a crash when road conditions were dry or slippery were more likely to have consumed alcohol (OR=2.44, IC=1.03-5.80). Alcohol consumption is associated with unsafe cycling practices, for example not using a helmet or drive in bad road conditions, and with being the cause of a road crash. Preventing or limiting alcohol consumption and corresponding testing of cyclists must be improved. Background Cycling, being easy, inexpensive and healthy, is becoming one of the most popular means of transport the world over; bicycles are increasingly used for getting to work (Bacchieri et al., 2010). The cyclist population is therefore growing and becoming much more diverse. Cyclists, however, are among the most vulnerable road users in traffic collisions. Indeed, cyclists, being less protected, less visible and more unstable, are likely suffer more severe consequences of road accidents than users of motorised vehicles. The number of cyclist injuries and deaths, already high, increases year by year (NHTSA s National Center for Statistics, 2012; European Road Safety Observatory, 2011). Factors known to be associated with the risk of accidents and accident-related injuries are: age, rider experience, time and day of the week on which the accident occurred, and environmental conditions; helmet use and alcohol and drug consumption are also important factors (Ministry of Transport - New Zeland, 2012; Crocker et al., 2012; Bacchieri et al., 2010; Berg et al., 2007; Andersson and Bunketorp, 2002). Road accidents have widely varying consequences, ranging from minor abrasions to fractures and death (Scheiman et al., 2010; Schwellnus and Derman, 2005). Different parts of the body can be involved (Abbas et al., 2011; Stranges et al., 2009; Abu-Zidan F.M. et al., 2007),
but the most serious injuries are those that involve the head and the spinal cord. These injuries have been found to be more frequent among cyclists who had abused alcohol and drugs and who were not wearing a protective helmet at the time of the accident (Li at al., 2001; Crocker et al., 2012; Airaksinen et al., 2010, Javouhey et al., 2006; Andersson and Bunkertorp, 2002; Li et al., 2000; Li et al., 1996). Aims The aim of this study, which analyses cyclists involved in collisions, is to establish which cyclist and accident characteristics are associated with alcohol consumption in this population. Methods The source used for the present analysis is the database of the German In-Depth Accident Study (GIDAS), which is the largest study of this kind in Germany. Whenever an accident occurs, the police, rescue services, and fire department headquarters in the areas of Hannover and Dresden immediately inform the research team that goes directly to the accident site and collect information on environmental conditions, road design, traffic control, accident details, vehicle damage and deformation, impact contact points, technical vehicle data, and information about the people involved. In addition to this information collected at the scene, the researchers subsequently collect more detailed measurements of the vehicle (usually following day) and further medical information about injuries sustained and treatments administered. The accident is then reconstructed in depth. Each year approximately 2,000 traffic accidents are documented in this way (GIDAS, 2012). All cyclists from the GIDAS database who were involved in a road accident between 2000 and 2010 and submitted to an alcohol test were selected for the present study. According to the limit set by German law, alcohol tests were classed as positive if the blood alcohol concentration (BAC) was equal to or greater than 0.05 mg/l. In the years 2000-2010, a total of 4,928 cyclists were involved in road accidents. Of these, 299 underwent an alcohol test following the collision. Alcohol test results were available for 242 cyclists, who were thus included in the present analysis; the 57 cyclists whose alcohol test results were not known were excluded from the analysis. Absolute and relative frequencies were used to describe the studied variables. To evaluate the severity of head trauma the Abbreviated Injury Scale (AIS) was used (Association for the Advancement of Automotive Medicine, 1990). Overall body injury severity was classified on the basis of the most severe injury sustained in each part of the body considered (MAIS). Cyclists with BACs over and those with BACs under the prescribed limit were compared. Comparisons were performed using a ² test, or Fisher test when appropriate. A logistic regression analysis was carried out to evaluate the association between each cyclist s BAC (dependent variable) and the following variables: helmet use, age, gender, responsibility, use of cycle path, type of accident, road conditions, area, speed limit, weather conditions, day of the week, and collision consequences (independent variables). Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated. Analyses were performed using the STATA software, version 10. Results In all, 242 cyclists involved in road accidents and submitted to alcohol testing were analysed. Of these, 104 (43.0%) were over the prescribed BAC limit and 206 (85.1%) were not wearing a helmet at the time of the accident. Fifty-one (21.4%) were aged 11-24 years, 162 (68.1%) 25-64 years, and 25 (10.5%) 65+ years; most (213, 88.4%) were male. In 133 (55.9%) cases, the cyclist was entirely responsible for the accident, and in 65 (16.8%) the other road user
was entirely responsible; in 34 (27.3%) cases they were both partially responsible. It emerged that 164 cyclists (69.8%) were not using a cycle path at the time of the accident. In 59 (24.4%) cases, the accident involved only the cyclist, whereas in 137 (56.6%) cases the cyclist collided with a motorised vehicle and in 46 (19.0%) with a non-motorised vehicle. Most of the accidents occurred on a dry road (204, 84.3%), in an urban area (195, 80.9%), with a speed limit 50 km/h (193, 81.1%), in good weather conditions (220, 90.9%), and on a weekday (181, 74.8%). Slight injuries (MAIS=1-2) were sustained by 194 (84.7%) of the cyclists, while severe injuries (MAIS 3) were recorded in 14 cases (6.1%). Head injuries were sustained by 129 (56.6%) (Table 1). The analysis of possible associations with alcohol consumption showed higher percentages of intoxicated cyclists among those who had not been wearing a helmet (59.7% vs 41.7%, p=0.044) and among the males (60.6 % vs 28.7%, p=0.001). As regards responsibility for the collision, the intoxication rate was highest (71.4%) among those who were at fault, 52.3% among those who were partially responsible, and 20.0% among those involved in a collision caused entirely by the other party involved (p<0.0001). The percentage of intoxicated cyclists was 47.4% among those who collided with a motorised vehicle, 60.9% among those involved in an accident with a non-motorised vehicle, and 76.3% among those involved in singlevehicle accidents (i.e. which involved no other party) (p=0.001). The percentage of intoxicated riders was higher in the group of cyclists who sustained head injuries compared with those who did not (62.8% vs 47.5%, p=0.021 (Table 1). In the multivariate analysis (Table 2), the variables helmet use, gender, and responsibility remained statistically significant: the odds of being intoxicated were 2.41 (CI: 1.08-5.38) times higher among cyclists who did not wear a helmet than among those who did; 0.23 (CI: 0.08-0.66) times lower among females than males; and 0.22 (CI: 0.08-0.61) times lower among cyclists who were not at fault in the collision compared with those who were partially at fault. Road conditions were correlated with alcohol consumption in the mutually adjusted analysis: cyclists who were involved in a crash when road conditions were dry or slippery were more likely to have consumed alcohol (OR=2.44, IC=1.03-5.80). Discussion and conclusions Of 242 cyclists involved in collisions, 43% had a BAC 0.05 mg/l. An association emerged between failure to wear a helmet at the time of the accident and a positive alcohol test. Cyclists travelling under the effect of alcohol are more likely to be at fault in an accident and they are more likely to be involved in a collision when road surface is slippery or wet. Females are less likely than males to cycle under the effect of alcohol. The present study reveals a clear association between alcohol consumption and cycle helmet use: cyclists with a BAC 0.05 mg/l are less likely than other cyclists to wear a safety helmet. This finding confirms the evidence emerging in previous studies, which showed that alcohol consumption in cyclists is associated with other unsafe riding behaviors, in particular, failure to use a helmet or ride in bad road conditions (Li et al. 2001, Airaksinen et al. 2010, Andersson and Bunketrop 2002, Crocker et al. 2010). The dismal rate of helmet use among BAC-positive cyclists is linked to alcohol-induced impairment of cognitive functions and safety behaviours. In addition, it is possible that people who ride bicycles after consuming alcohol are less likely than other cyclists to own a safety helmet, or to opt to wear a helmet when one is available. Moreover, some bicycle riders underestimate the seriousness of cycling after drinking alcohol, and these individuals probably also underestimate both the degree to which their ability to operate a bicycle is impaired after drinking and the ensuing risks. Injury prevention should be directed at changing attitudes towards cycling while under the influence of alcohol and at promoting the use of bicycle helmets.
In agreement with the findings of Martínez-Ruiz et al. (2013), the results of the present study show that cyclists with a blood alcohol level higher than the legally prescribed limit are more likely to be responsible for accidents. This is probably due to an alcohol-induced loss of attention, lucidity and stability, which makes the cyclist a danger to himself and to other road users. In this study the males were found to be more likely than the females to ride a bicycle under the influence of alcohol, confirming previous findings in the literature (Airaksinen et al. 2010, Li et al 1996), revealed an association between gender and alcohol consumption in cyclists who are involved in collisions. The explanation for this finding may be related to differences in the behaviour of male and female cyclists. It is possible that male cyclists are more inclined to take risks and mind less about the social disapproval attached to certain behaviours such as drinking and driving. The present study showed a higher rate of head injuries among the cyclists with a positive alcohol test, even though this association was not significant on the multivariate analysis. Higher rates of head injuries among cyclists riding under the influence of alcohol were also reported in previous studies (Andersson and Bunketorp, 2002, Crocker et al., 2010, Crocker et al., 2012). A main reason for the association between alcohol consumption and injury is the deleterious impact of alcohol on psychomotor skills, cognitive functions, and safety behaviours. As a result, cyclists under the influence of alcohol find it difficult to keep their balance, negotiate traffic, and perceive and respond to hazardous situations. The fact that the intoxicated cyclists sustained injuries to the head and face to a much greater extent than the sober cyclists may be due to impairment of their ability to react, and thus to take action to protect themselves when they fell. This study presents three main limitations, all concerning missing data. One is the low number of subjects submitted to the alcohol test; exclusion of those not tested drastically reduced the initial sample size: from 4928 to 299. The low rate of alcohol testing is due to the fact that the police do not routinely test cyclists involved in traffic accidents, only those suspected of having consumed alcohol or drugs (i.e. those seeming mentally confused or unsteady or having alcohol-smelling breath, watery or bloodshot eyes, slow or slurred speech, etc.). Moreover, in 57 of the 299 tested cyclists, the results of the alcohol test were not available: in these cases, no medical report was produced due to problems with the blood sample. The characteristics of the cyclists whose alcohol test results were lacking were, however, similar to those for whom we did have test results. The only variable that differed significantly between the two groups was age (p=0.037) (data not shown). Finally, a high percentage of missing data for some of the collected variables prevented us from analysing several interesting possible risk factors identified in the literature. However, there is no reason to believe these potential biases had any systematic impact on the results of this methodologically rigorous study. In conclusion, showing that alcohol consumption in cyclists is associated with other unsafe riding behaviors, in particular, failure to use a helmet or drive in bad road conditions, and with being the cause of a road crash could be useful for the future development of injury prevention strategies. Particular attention should be paid to men riders. Preventing or limiting alcohol consumption and corresponding testing of cyclists must be improved. References Abbas, A.K., Hefny, A. F., & Abu-Zidan, F. M. (2011). Seatbelts and road traffic collision injuries. World Journal of Emergency Surgery, 6, 1 6.
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Stranges, E., Uscher-Pines, L., & Stocks, C. (2009). Statistical Brief#135. In Healthcare Cost and Utilization Project (HCUP), Emergency Department Visits and Hospital Inpatient Stays for Bicycle-Related Injuries. Rockville, MD: Agency for Health Care Policy and Research (US). Table 1. Sample description (n=242) Variables n BAC 0.05 (%) p Variables n BAC 0.05 (%) BAC 104 43.0 Age (years) 0.347 Use of helmet 0.044 11-24 51 49.0 0.276 No 206 59.7 25-64 162 59.9 0.295 Yes 36 41.7 65+ 25 52.0 0.900 Responsibility <0.001 Gender 0.001 Cyclist alone 133 71.4 <0.001 Male 213 60.6 Other party alone 40 20.0 <0.001 Female 28 28.6 Both 65 52.3 0.315 Road conditions 0.406 Use of cycle path 0.476 Dry 204 55.9 No 164 58.5 Wet/slippery 38 63.2 Yes 71 53.5 Area 0.053 Collision partner 0.001 Urban 195 53.8 Single-vehicle 59 76.3 0.001 Extra-urban 46 69.6 Motorised vehicle 137 47.4 0.001 Speed limit (km/h) 0.861 Non-motorised vehic. 46 60.9 0.558 <50 45 55.6 Maximum AIS 0.409 50 193 57.0 0 21 61.9 0.589 Weather conditions 0.485 1-2 194 54.6 0.224 Good 220 57.7 3-6 14 71.4 0.278* Bad 22 50.0 Head trauma (AIS) 0.021 Day of week 0.336 No (0) 99 47.5 Monday-Friday 181 55.2 Yes (1-6) 129 62.8 Saturday/Sunday 61 62.3 *Fisher s exact test Table 2. Factors associated with alcohol use (n=234) Variable OR CI p Use of helmet No vs Yes 2.41 1.08 5.38 0.032 Age 25-64 vs 11-24 1.90 0.92 3.92 0.082 Age 65+ vs 11-24 0.83 0.30 2.31 0.720 Gender Female vs Male 0.23 0.08 0.66 0.006 Fault Cyclist vs Both 1.84 0.90 3.78 0.096 Fault Other vs Both 0.22 0.08 0.61 0.004 Type of accident Motorised vehicle vs single-vehicle 0.54 0.22 1.30 0.168 Type of accident Non-motorised vehicle vs single-vehicle 0.57 0.21 1.52 0.257 Road conditions Wet/slippery vs Dry 2.44 1.03 5.80 0.042 p