A decrease in both mild and severe bicycle-related head injuries in helmet wearing ages--trend analyses in Sweden.

Several international studies point at the efficacy of bicycle helmets in reducing head injuries. In Sweden, observational studies show that from 1988 to 1996 helmet use increased in all categories of cyclists. The objectives of this study were to analyse the trends of bicycle-related head injuries based on their main diagnosis and external cause of injury by different age groups. Our study area was the whole population of Sweden from 1987 to 1996. Outcome evaluation was based on data from the Swedish National Hospital Discharge Register concerning all bicycle-related injuries from 1987 to 1996, which presented 49 758 reported in-patient care. The trends in incidence rates (IRs) were studied with regression analyses. The results show that children under 15 years had the highest IRs. For these children, the IR decreased by 46%. The head injuries in children decreased both in collisions with motor vehicles and in other accidents. Similarly, the IR of concussion and skull fracture decreased. For non-head injuries, there were no significant changes for children. On the other hand, the incidence of both head and other injuries for adults aged 16-50 years increased. Ages above that showed no significant changes. Our conclusions are that the decrease in IR for bicycle-related head injuries refers to children in ages for whom bicycle helmet use during the period increased. This could not be explained by any general decrease in bicycle-related accidents or by any changes in the distribution of injuries after collision with motor vehicles. The increasing helmet use among younger schoolchildren probably contributed to the decrease in head injuries.