A systematic review of correct bicycle helmet use: how varying definitions and study quality influence the results

Background: Bicycle helmets effectively reduce the risk of bicycle-related head injuries and trauma; however, they must fit properly to be effective. Little is known about the prevalence of correctly worn helmets and factors associated with proper helmet use. Objective: To examine proper bicycle helmet use through a systematic review. Methods: Comprehensive searches of electronic medical databases were performed, and completed by grey literature and reference list checks to identify eligible studies. Studies eligible for inclusion had to involve cyclists and report on the prevalence of correct or incorrect helmet use. Two reviewers independently selected studies and data were extracted regarding the prevalence and factors influencing proper helmet wearing of cyclists. Results: An inclusive search strategy led to 2285 prescreened citations; 11 of the studies were finally included in the review. Overall, correct helmet use varied from 46% to 100%, depending on the criteria used by researchers to define proper helmet use; stricter criteria reduced the proportion of properly worn helmets. Adulthood, female sex and educational interventions were associated with correct helmet use in some studies. Self-reported poor helmet fit (OR = 1.96; 95% CI 1.10 to 3.75), posterior positioning of helmet (OR = 1.52; 95% CI 1.02 to 2.26) and helmet loss in crash (OR = 3.25; 95% CI 1.82 to 5.75) increased the risk of head injury. In addition, educational programmes on helmet use in schools increased correct helmet use among schoolchildren. Conclusions: This systematic review outlines the current state of the literature including the variability in research methodology and definitions used to study proper helmet-wearing behaviour among cyclists.