Bicyclists Injured by Automobiles: Relationship of Age to Injury Type and Severity--a National Trauma Databank Analysis

Background: Bicycle riding is a popular recreational activity and a common mode of transportation. Impact with a motor vehicle, however, has the potential to result in significant injury to the rider. The magnitude of this problem, the incidence and types of injuries, and the effect of age on these variables are poorly defined in the literature.

Methods: This was a National Trauma Databank study during a 5-year period. Injury Severity Score (ISS), specific injuries sustained by riders, and outcomes were analyzed according to age groups (≤ 14 years, 15-35 years, 36-55 years, 56-65 years, and >65 years).

Results: During the study period, there were 12,429 admissions as a result of bicycle-related injuries involving motor vehicles (0.7% of all trauma admissions). There were 4,095 patients (32.9%) ≤ 14 years, 3,806 (30.7%) 15 to 35 years, 3,413 (27.5%) 36 to 55 years, 688 (5.5%) 56 to 65 years, and 427 (3.4%) >65 years. The incidence of severe or critical trauma (ISS ≥ 16) in the five age strata was 20.3%, 19.2%, 26.4%, 33.4%, and 38.2%, respectively (p < 0.001). The most commonly encountered injuries consisted of extremity fractures (34.9%). Patients ≤ 14 years old were significantly more likely to suffer fractures to the lower extremity and less likely to sustain fractures to the upper extremity. The overall incidence of head injury was 28.3% and increased in a stepwise fashion with increasing age, ranging from 26.5% in the age stratum 15 to 35 years to 38.6% in the age stratum >65 years, p < 0.001. The overall mortality was 3.7% and ranged from 2.4% in the age stratum ≤ 14 years, to 12.2% in the stratum >65 years. After adjusting for differences in age groups, there was a stepwise increase in the risk of death for bicyclists >65 years old who were 10-fold more likely to die than those ≤ 14 years old (adj. p < 0.001).

Conclusion: Bicycle-related injuries involving motor vehicles are associated with a high incidence of head injuries and extremity fractures. Age plays a critical role in the severity and anatomic distribution of injuries sustained, with a stepwise increase in mortality with increasing age. Further evaluation of specific preventative measures, especially for elderly bicyclists is warranted.