"It is a bit counterintuitive that we don't see an effect of helmet laws on head injuries," said University of Toronto researcher Jessica Dennis, whose work was published Tuesday in the journal of the British Medical Association.
"But there's so many other things going on at the same time a helmet law is passed that it's really hard to say that helmet law was the reason head injuries decrease."
Dennis, herself a daily cyclist with a 30-minute commute to downtown Toronto, compiled information countrywide on more than 66,000 hospital admissions for cycling-related head injuries between 1994 and 2008. She compared how those injury rates changed over time between provinces that had mandatory helmet laws and those that didn't.
She found admission rates for provinces with legislation dropped 54 per cent for young people between 1994 and 2003, the period during which the laws were being brought in.
But Dennis also found rates dropping in provinces without legislation — although, at 33 per cent, not quite so steeply. She also found helmet laws produced little change in adult admission rates, which were low and stable throughout the study period.
Dennis found that in every province with legislation, the decline in hospital admissions for head-related cycling injuries actually started years before a law was introduced. Nor did the rate of that decline change with legislation.
She couldn't find any statistical link between helmet laws and reduced hospital admissions.
"We were unable to detect an independent effect of legislation on the rate of hospital admissions," the report concludes.
The study, the most extensive to date and the first to compare hospital admissions between provinces with and without helmet laws, suggests there's a lot more to making cyclists safe than forcing them to wear head gear.
"It's a complex social intervention that's happening," Dennis said.
Cities have installed cycling infrastructure such as bike lanes. Some communities have passed safe-passing laws that require motorists to move over as they drive by bikes.
Many cyclists have adopted helmets on their own without being required to by law. Education campaigns for riders and drivers have been created.
And there are just more people on bikes.
"There's something to be said for safety in numbers."
Dennis's previous research has debunked theories that helmet laws reduce ridership and has shown that kids are more likely to wear helmets in provinces requiring both young and adult riders to do so.
Now her latest paper suggests that helmet laws don't have the safety impact they're cracked up to have.
"Helmet laws are attractive because they're cheap and they're easy to implement. But as our study shows, they shouldn't be the only solution because it's not enough.
"Helmet laws should be part of a comprehensive strategy to improve cycling safety."
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