Fact

Bicycle helmets - Do bicycle helmets protect cyclists from (fatal) head injury?

Yes: according to three independent sources – biomechanical research, simulation research, and case‑control research – a bicycle helmet reduces the risk of head and/or brain injury in case of a crash or fall.

In biomechanical research bicycle helmets are tested in the laboratory on their shock-absorbing effect. In a test in which a head-shaped form  fell down a distance of one and a half metres it was estimated that the bicycle helmet reduced the risk of serious brain injury by almost 100% to about 10% (Cripton et al., 2014). The helmets that were tested, complied with the mandatory bicycle helmet standard in the US. This CPSC-standard uses slightly higher requirements than the European EN-1078-standard (see e.g. Mizuno et al. (2014) for a comparison of test conditions of different standards).

In simulation research, both the physical forces that act on the head and the possible protective effect of a helmet are simulated in a model. Based on computer simulations of three types of bicycle crashes, Fahlstedt et al. (2016) established that a bicycle helmet could diminish the risk of concussion by more than 50% and the risk of a skull fracture by more than 90%. 

In case-control research the head or brain injury of cyclists who do or who do not wear a helmet is compared. The meta-analysis by Olivier & Creighton (2016) is the most recent and extensive overview of so-called case-control studies of the protective effect of a bicycle helmet. Olivier & Creighton estimate that the risk of severe head injury decreased by 69% and that of fatal head injury by 65%. The estimates in this meta-analysis are based on 40 case-control studies. In these studies the injuries of a total of 64,000 cycling casualties with and without helmet were compared.

Case-control studies on bicycle helmets have been criticized, because the statistical analysis would lead to an overestimation of the protective effect. Also the frequently used control group (cyclists in the emergency department of a hospital with other injuries than head injury) may differ on important aspects? – such as cycling behaviour and distance travelled by bicycle – from the cases (cyclists with a head wound; see e.g. Zeegers, 2015). Although these points are justifiable to some extent, we do not expect that they can explain the total effect found by the case-control studies. Besides, most of the case-control studies were performed in the United States, Canada and Australia, where the traffic infrastructure is different from that in Netherlands. Bicycle crashes may therefore also be different, and this can potentially affect the estimation of the protective effect of bicycle helmets. No case-control studies of the protective effect of bicycle helmets have as yet been executed in the Netherlands.

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