Helmet legislation and admissions to hospital for cycling related head injuries in Canadian provinces and territories: interrupted time series analysis

OBJECTIVE To investigate the association between helmet legislation and admissions to hospital for cycling related head injuries among young people and adults in Canada. DESIGN Interrupted time series analysis using data from the National Trauma Registry Minimum Data Set. SETTING Canadian provinces and territories; between 1994 and 2003, six of 10 provinces implemented helmet legislation. PARTICIPANTS All admissions (n=66,716) to acute care hospitals in Canada owing to cycling related injury between 1994 and 2008. MAIN OUTCOME MEASURE Rate of admissions to hospital for cycling related head injuries before and after the implementation of provincial helmet legislation. RESULTS Between 1994 and 2008, 66,716 hospital admissions were for cycling related injuries in Canada. Between 1994 and 2003, the rate of head injuries among young people decreased by 54.0% (95% confidence interval 48.2% to 59.8%) in provinces with helmet legislation compared with 33.1% (23.3% to 42.9%) in provinces and territories without legislation. Among adults, the rate of head injuries decreased by 26.0% (16.0% to 36.3%) in provinces with legislation but remained constant in provinces and territories without legislation. After taking baseline trends into consideration, however, we were unable to detect an independent effect of legislation on the rate of hospital admissions for cycling related head injuries. CONCLUSIONS Reductions in the rates of admissions to hospital for cycling related head injuries were greater in provinces with helmet legislation, but injury rates were already decreasing before the implementation of legislation and the rate of decline was not appreciably altered on introduction of legislation. While helmets reduce the risk of head injuries and we encourage their use, in the Canadian context of existing safety campaigns, improvements to the cycling infrastructure, and the passive uptake of helmets, the incremental contribution of provincial helmet legislation to reduce hospital admissions for head injuries seems to have been minimal.