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Evaluating the impact of cycle helmet use on severe traumatic brain injury and death in a national cohort of over 11000 pedal cyclists: a retrospective study from the NHS England Trauma Audit and Research Network dataset
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    Claims of cycle helmet benefit: Selection bias has a stronger claim as explanatory factor.

    In their recent paper Dodds et al. analysed cycling-related injuries recorded in the NHS England Trauma Audit and Research Network (TARN) Database for the period from 14 March 2012 to 30 September 2017(Dodds et al., 2019). They claim their methods show an association between cycle helmet use and reductions in, crude 30-day mortality, severe traumatic brain injury (TBI), intensive care unit requirement and neurosurgical intervention. Cycle helmets are light structures, generally weighing 250g to 600g, and are typically composed of a thin shell of stiff plastic outside a thicker shell of expanded polystyrene foam. The standard approval tests simulate simple falls, with no other vehicles involved (ROSPA, 2018). They are not rated for high-energy impacts involving moving motor vehicles. Eighty four per cent of fatality and serious cyclist accidents reported to the police involve motor vehicles (ROSPA, 2017). Cycle helmets are shaped to "cup" the top of the skull rather than enclose the head, which means they need a system of well-adjusted straps to stay attached in the event of a crash. When worn by non-enthusiast cyclists they are often poorly adjusted or the wrong size (Parkinson and Hike, 2003; Thai et al., 2015). When claims are made of "significant correlation between use of cycle helmets and reduction in adjusted mortality and morbidity associated with TBI and facial injury" (Dodds et al., 2019), then some observers will be immediately sceptical an...

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    Conflict of Interest:
    I have been a volunteer advocate for active travel for most of my adult life.