Potential impact of mandatory helmet when biking.

INTRODUCTION

Head injuries are a common and severe outcome of bicycle-related incidents, but they are preventable with a helmet. In Denmark, helmet use is not mandatory, and only half of cyclists wear helmets. Estimating the prevention potential of mandatory helmet use may inform evidence-based injury prevention policy. We aimed to estimate the number of preventable head injuries and severe head injuries under mandatory helmet use in 2020 and 2024.

METHODS

We conducted a retrospective study using emergency department data from Odense and Svendborg University Hospital, where helmet use is systematically recorded. Cyclists treated for head injuries (minor or major) following bicycle-related incidents were included. The potential impact of mandatory helmet use was estimated-, assuming a post-legislation helmet use rate of 92%, based on evidence from New Zealand. A switch fraction was applied to account for compliance, and meta-analytic-based relative risk reductions of 48% for minor injuries and 60% for severe head injuries were used to estimate the number of potentially preventable head injuries.

RESULTS

In total, 2,393 cyclists were treated for minor or major head injuries during the five-year period (1,366 (57%) unhelmeted). Overall, 57% were male, and the mean age was 38 years (SD 21 years). Severe head injuries were sustained by 511 cyclists, 275 of whom (53%) were unhelmeted. Extrapolation suggests that approximately 5,733 minor and 1,806 severe head injuries could have been prevented.

CONCLUSION

The findings support helmet use as an effective prevention strategy to reduce head injuries among bicyclists.

FUNDING: None.

TRIAL REGISTRATION: Not relevant.