Bicycle-related trauma represents an essential percentage of road traffic victims worldwide2,10. The increasing diffusion of this type of transport responds to anti-pollution policies, representing a valid alternative method of mobility in heavy-traffic urban areas11. Bicycle mobility was also improved by the diffusion of different bike sharing companies worldwide, that have made this popular type of transport easily available in a few minutes11. Given the high diffusion of bicycle use both for sport and transport purposes, analysing the kind of injuries and the mortality distribution of these types of trauma is of paramount importance.
Our study confirmed head and chest injuries as independent predictors of mortality only in patients over 55 years old, as showed in Table 2. Aggravating factors influenced the mortality trends, as roll-on and roll-over were independent predictors of mortality in patients ≥ 55 years old. The throw was an independent predictor of mortality between 18 and 54 years old (Table 3). Only 44 patients (9.8 %) were not wearing helmets in our study. Only one patient died among them, in the group 18–54 years old. In our research, not wearing a helmet was not an independent predictor of mortality, but head and chest AIS ≥ 3 were independent predictors of death. Therefore, despite the protective effect of the helmet, other variables should influence the mortality trends in cycle trauma. These results align with the study of Foley J. et al.3, who showed that different variables (i.e., gender and mechanism of trauma) were independent predictors of mortality in bicycle trauma, and other factors than wearing a helmet could have a role in head injuries. A systematic review conducted by Hoye A.12 showed that mandatory bicycle helmet legislation for all cyclists reduces about 20% of head injuries, significantly affecting severe head injuries. Two meta-analyses13,14 confirmed the positive impact of the helmet only on severe head injuries, also showing a protective result on fatal injury prevention. However, all the studies agreed13,14 on the role of different variables on bicycle mortality.
The survival rate estimated with the Kaplan-Mayer method showed a higher mortality in patients with an ISS ≥ 25, confirming that overall trauma severity influenced mortality.
However, as shown in Fig. 1, patients older than 55 years showed the lowest survival rate, confirming age as an independent predictor of mortality. Interestingly, another study on motorcycle-related trauma9 showed similar results, with a higher mortality trend in older patients (≥ 55 years old).
Finally, Fig. 2 shows the seasonal distribution of bicycle trauma, more frequent in summer (34%), followed by spring (28.9%). These results align with current literature15.
Given its retrospective nature, this study presents some limitations. Although older patients showed a higher mortality rate, it’s possible that patients’ comorbidities and the use of anticoagulant therapy could influence the prognosis. Unfortunately, these variables were not available in our trauma registry and were not considered.
Moreover, although this study was conducted in a level-one trauma center in Italy, no information on prehospital trauma mortality was available. Indeed, our data referred only to our in-hospital experience.
Finally, despite different studies showing a possible correlation between the bicycle infrastructure and mortality16,17, this variable is not reported in our trauma registry, and it has not been considered.
In conclusion, this study showed that different variables influenced bicycle trauma mortality. Older age and aggravating factors are independent predictors of mortality. Despite the protective effect of the helmet, head and chest injuries were confirmed to be independent predictors of mortality in patients ≥ 55 years old. Bicycle-related trauma is more frequent during the warm seasons, especially in July and August. Further multicentric and prospective studies should be advisable to confirm our results, fostering a stronger scientific collaboration with the prehospital care services.